diff --git a/src/modules/audio_coding/codecs/ilbc/documentation/rfc3951.txt b/src/modules/audio_coding/codecs/ilbc/documentation/rfc3951.txt deleted file mode 100644 index d4fba08e4..000000000 --- a/src/modules/audio_coding/codecs/ilbc/documentation/rfc3951.txt +++ /dev/null @@ -1,10867 +0,0 @@ - - - - - - -Network Working Group S. Andersen -Request for Comments: 3951 Aalborg University -Category: Experimental A. Duric - Telio - H. Astrom - R. Hagen - W. Kleijn - J. Linden - Global IP Sound - December 2004 - - - Internet Low Bit Rate Codec (iLBC) - -Status of this Memo - - This memo defines an Experimental Protocol for the Internet - community. It does not specify an Internet standard of any kind. - Discussion and suggestions for improvement are requested. - Distribution of this memo is unlimited. - -Copyright Notice - - Copyright (C) The Internet Society (2004). - -Abstract - - This document specifies a speech codec suitable for robust voice - communication over IP. The codec is developed by Global IP Sound - (GIPS). It is designed for narrow band speech and results in a - payload bit rate of 13.33 kbit/s for 30 ms frames and 15.20 kbit/s - for 20 ms frames. The codec enables graceful speech quality - degradation in the case of lost frames, which occurs in connection - with lost or delayed IP packets. - - - - - - - - - - - - - - - - - -Andersen, et al. Experimental [Page 1] - -RFC 3951 Internet Low Bit Rate Codec December 2004 - - -Table of Contents - - 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4 - 2. Outline of the Codec . . . . . . . . . . . . . . . . . . . . . 5 - 2.1. Encoder. . . . . . . . . . . . . . . . . . . . . . . . . 5 - 2.2. Decoder. . . . . . . . . . . . . . . . . . . . . . . . . 7 - 3. Encoder Principles . . . . . . . . . . . . . . . . . . . . . . 7 - 3.1. Pre-processing . . . . . . . . . . . . . . . . . . . . . 9 - 3.2. LPC Analysis and Quantization. . . . . . . . . . . . . . 9 - 3.2.1. Computation of Autocorrelation Coefficients. . . 10 - 3.2.2. Computation of LPC Coefficients. . . . . . . . . 11 - 3.2.3. Computation of LSF Coefficients from LPC - Coefficients . . . . . . . . . . . . . . . . . . 11 - 3.2.4. Quantization of LSF Coefficients . . . . . . . . 12 - 3.2.5. Stability Check of LSF Coefficients. . . . . . . 13 - 3.2.6. Interpolation of LSF Coefficients. . . . . . . . 13 - 3.2.7. LPC Analysis and Quantization for 20 ms Frames . 14 - 3.3. Calculation of the Residual. . . . . . . . . . . . . . . 15 - 3.4. Perceptual Weighting Filter. . . . . . . . . . . . . . . 15 - 3.5. Start State Encoder. . . . . . . . . . . . . . . . . . . 15 - 3.5.1. Start State Estimation . . . . . . . . . . . . . 16 - 3.5.2. All-Pass Filtering and Scale Quantization. . . . 17 - 3.5.3. Scalar Quantization. . . . . . . . . . . . . . . 18 - 3.6. Encoding the Remaining Samples . . . . . . . . . . . . . 19 - 3.6.1. Codebook Memory. . . . . . . . . . . . . . . . . 20 - 3.6.2. Perceptual Weighting of Codebook Memory - and Target . . . . . . . . . . . . . . . . . . . 22 - 3.6.3. Codebook Creation. . . . . . . . . . . . . . . . 23 - 3.6.3.1. Creation of a Base Codebook . . . . . . 23 - 3.6.3.2. Codebook Expansion. . . . . . . . . . . 24 - 3.6.3.3. Codebook Augmentation . . . . . . . . . 24 - 3.6.4. Codebook Search. . . . . . . . . . . . . . . . . 26 - 3.6.4.1. Codebook Search at Each Stage . . . . . 26 - 3.6.4.2. Gain Quantization at Each Stage . . . . 27 - 3.6.4.3. Preparation of Target for Next Stage. . 28 - 3.7. Gain Correction Encoding . . . . . . . . . . . . . . . . 28 - 3.8. Bitstream Definition . . . . . . . . . . . . . . . . . . 29 - 4. Decoder Principles . . . . . . . . . . . . . . . . . . . . . . 32 - 4.1. LPC Filter Reconstruction. . . . . . . . . . . . . . . . 33 - 4.2. Start State Reconstruction . . . . . . . . . . . . . . . 33 - 4.3. Excitation Decoding Loop . . . . . . . . . . . . . . . . 34 - 4.4. Multistage Adaptive Codebook Decoding. . . . . . . . . . 35 - 4.4.1. Construction of the Decoded Excitation Signal. . 35 - 4.5. Packet Loss Concealment. . . . . . . . . . . . . . . . . 35 - 4.5.1. Block Received Correctly and Previous Block - Also Received. . . . . . . . . . . . . . . . . . 35 - 4.5.2. Block Not Received . . . . . . . . . . . . . . . 36 - - - - -Andersen, et al. Experimental [Page 2] - -RFC 3951 Internet Low Bit Rate Codec December 2004 - - - 4.5.3. Block Received Correctly When Previous Block - Not Received . . . . . . . . . . . . . . . . . . 36 - 4.6. Enhancement. . . . . . . . . . . . . . . . . . . . . . . 37 - 4.6.1. Estimating the Pitch . . . . . . . . . . . . . . 39 - 4.6.2. Determination of the Pitch-Synchronous - Sequences. . . . . . . . . . . . . . . . . . . . 39 - 4.6.3. Calculation of the Smoothed Excitation . . . . . 41 - 4.6.4. Enhancer Criterion . . . . . . . . . . . . . . . 41 - 4.6.5. Enhancing the Excitation . . . . . . . . . . . . 42 - 4.7. Synthesis Filtering. . . . . . . . . . . . . . . . . . . 43 - 4.8. Post Filtering . . . . . . . . . . . . . . . . . . . . . 43 - 5. Security Considerations. . . . . . . . . . . . . . . . . . . . 43 - 6. Evaluation of the iLBC Implementations . . . . . . . . . . . . 43 - 7. References . . . . . . . . . . . . . . . . . . . . . . . . . . 43 - 7.1. Normative References . . . . . . . . . . . . . . . . . . 43 - 7.2. Informative References . . . . . . . . . . . . . . . . . 44 - 8. ACKNOWLEDGEMENTS . . . . . . . . . . . . . . . . . . . . . . . 44 - APPENDIX A: Reference Implementation . . . . . . . . . . . . . . . 45 - A.1. iLBC_test.c. . . . . . . . . . . . . . . . . . . . . . . 46 - A.2 iLBC_encode.h. . . . . . . . . . . . . . . . . . . . . . 52 - A.3. iLBC_encode.c. . . . . . . . . . . . . . . . . . . . . . 53 - A.4. iLBC_decode.h. . . . . . . . . . . . . . . . . . . . . . 63 - A.5. iLBC_decode.c. . . . . . . . . . . . . . . . . . . . . . 64 - A.6. iLBC_define.h. . . . . . . . . . . . . . . . . . . . . . 76 - A.7. constants.h. . . . . . . . . . . . . . . . . . . . . . . 80 - A.8. constants.c. . . . . . . . . . . . . . . . . . . . . . . 82 - A.9. anaFilter.h. . . . . . . . . . . . . . . . . . . . . . . 96 - A.10. anaFilter.c. . . . . . . . . . . . . . . . . . . . . . . 97 - A.11. createCB.h . . . . . . . . . . . . . . . . . . . . . . . 98 - A.12. createCB.c . . . . . . . . . . . . . . . . . . . . . . . 99 - A.13. doCPLC.h . . . . . . . . . . . . . . . . . . . . . . . .104 - A.14. doCPLC.c . . . . . . . . . . . . . . . . . . . . . . . .104 - A.15. enhancer.h . . . . . . . . . . . . . . . . . . . . . . .109 - A.16. enhancer.c . . . . . . . . . . . . . . . . . . . . . . .110 - A.17. filter.h . . . . . . . . . . . . . . . . . . . . . . . .123 - A.18. filter.c . . . . . . . . . . . . . . . . . . . . . . . .125 - A.19. FrameClassify.h. . . . . . . . . . . . . . . . . . . . .128 - A.20. FrameClassify.c. . . . . . . . . . . . . . . . . . . . .129 - A.21. gainquant.h. . . . . . . . . . . . . . . . . . . . . . .131 - A.22. gainquant.c. . . . . . . . . . . . . . . . . . . . . . .131 - A.23. getCBvec.h . . . . . . . . . . . . . . . . . . . . . . .134 - A.24. getCBvec.c . . . . . . . . . . . . . . . . . . . . . . .134 - A.25. helpfun.h. . . . . . . . . . . . . . . . . . . . . . . .138 - A.26. helpfun.c. . . . . . . . . . . . . . . . . . . . . . . .140 - A.27. hpInput.h. . . . . . . . . . . . . . . . . . . . . . . .146 - A.28. hpInput.c. . . . . . . . . . . . . . . . . . . . . . . .146 - A.29. hpOutput.h . . . . . . . . . . . . . . . . . . . . . . .148 - A.30. hpOutput.c . . . . . . . . . . . . . . . . . . . . . . .148 - - - -Andersen, et al. Experimental [Page 3] - -RFC 3951 Internet Low Bit Rate Codec December 2004 - - - A.31. iCBConstruct.h . . . . . . . . . . . . . . . . . . . . .149 - A.32. iCBConstruct.c . . . . . . . . . . . . . . . . . . . . .150 - A.33. iCBSearch.h. . . . . . . . . . . . . . . . . . . . . . .152 - A.34. iCBSearch.c. . . . . . . . . . . . . . . . . . . . . . .153 - A.35. LPCdecode.h. . . . . . . . . . . . . . . . . . . . . . .163 - A.36. LPCdecode.c. . . . . . . . . . . . . . . . . . . . . . .164 - A.37. LPCencode.h. . . . . . . . . . . . . . . . . . . . . . .167 - A.38. LPCencode.c. . . . . . . . . . . . . . . . . . . . . . .167 - A.39. lsf.h. . . . . . . . . . . . . . . . . . . . . . . . . .172 - A.40. lsf.c. . . . . . . . . . . . . . . . . . . . . . . . . .172 - A.41. packing.h. . . . . . . . . . . . . . . . . . . . . . . .178 - A.42. packing.c. . . . . . . . . . . . . . . . . . . . . . . .179 - A.43. StateConstructW.h. . . . . . . . . . . . . . . . . . . .182 - A.44. StateConstructW.c. . . . . . . . . . . . . . . . . . . .183 - A.45. StateSearchW.h . . . . . . . . . . . . . . . . . . . . .185 - A.46. StateSearchW.c . . . . . . . . . . . . . . . . . . . . .186 - A.47. syntFilter.h . . . . . . . . . . . . . . . . . . . . . .190 - A.48. syntFilter.c . . . . . . . . . . . . . . . . . . . . . .190 - Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . .192 - Full Copyright Statement . . . . . . . . . . . . . . . . . . . . .194 - -1. Introduction - - This document contains the description of an algorithm for the coding - of speech signals sampled at 8 kHz. The algorithm, called iLBC, uses - a block-independent linear-predictive coding (LPC) algorithm and has - support for two basic frame lengths: 20 ms at 15.2 kbit/s and 30 ms - at 13.33 kbit/s. When the codec operates at block lengths of 20 ms, - it produces 304 bits per block, which SHOULD be packetized as in [1]. - Similarly, for block lengths of 30 ms it produces 400 bits per block, - which SHOULD be packetized as in [1]. The two modes for the - different frame sizes operate in a very similar way. When they - differ it is explicitly stated in the text, usually with the notation - x/y, where x refers to the 20 ms mode and y refers to the 30 ms mode. - - The described algorithm results in a speech coding system with a - controlled response to packet losses similar to what is known from - pulse code modulation (PCM) with packet loss concealment (PLC), such - as the ITU-T G.711 standard [4], which operates at a fixed bit rate - of 64 kbit/s. At the same time, the described algorithm enables - fixed bit rate coding with a quality-versus-bit rate tradeoff close - to state-of-the-art. A suitable RTP payload format for the iLBC - codec is specified in [1]. - - Some of the applications for which this coder is suitable are real - time communications such as telephony and videoconferencing, - streaming audio, archival, and messaging. - - - - -Andersen, et al. Experimental [Page 4] - -RFC 3951 Internet Low Bit Rate Codec December 2004 - - - Cable Television Laboratories (CableLabs(R)) has adopted iLBC as a - mandatory PacketCable(TM) audio codec standard for VoIP over Cable - applications [3]. - - This document is organized as follows. Section 2 gives a brief - outline of the codec. The specific encoder and decoder algorithms - are explained in sections 3 and 4, respectively. Appendix A provides - a c-code reference implementation. - - The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", - "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this - document are to be interpreted as described in BCP 14, RFC 2119 [2]. - -2. Outline of the Codec - - The codec consists of an encoder and a decoder as described in - sections 2.1 and 2.2, respectively. - - The essence of the codec is LPC and block-based coding of the LPC - residual signal. For each 160/240 (20 ms/30 ms) sample block, the - following major steps are performed: A set of LPC filters are - computed, and the speech signal is filtered through them to produce - the residual signal. The codec uses scalar quantization of the - dominant part, in terms of energy, of the residual signal for the - block. The dominant state is of length 57/58 (20 ms/30 ms) samples - and forms a start state for dynamic codebooks constructed from the - already coded parts of the residual signal. These dynamic codebooks - are used to code the remaining parts of the residual signal. By this - method, coding independence between blocks is achieved, resulting in - elimination of propagation of perceptual degradations due to packet - loss. The method facilitates high-quality packet loss concealment - (PLC). - -2.1. Encoder - - The input to the encoder SHOULD be 16 bit uniform PCM sampled at 8 - kHz. It SHOULD be partitioned into blocks of BLOCKL=160/240 samples - for the 20/30 ms frame size. Each block is divided into NSUB=4/6 - consecutive sub-blocks of SUBL=40 samples each. For 30 ms frame - size, the encoder performs two LPC_FILTERORDER=10 linear-predictive - coding (LPC) analyses. The first analysis applies a smooth window - centered over the second sub-block and extending to the middle of the - fifth sub-block. The second LPC analysis applies a smooth asymmetric - window centered over the fifth sub-block and extending to the end of - the sixth sub-block. For 20 ms frame size, one LPC_FILTERORDER=10 - linear-predictive coding (LPC) analysis is performed with a smooth - window centered over the third sub-frame. - - - - -Andersen, et al. Experimental [Page 5] - -RFC 3951 Internet Low Bit Rate Codec December 2004 - - - For each of the LPC analyses, a set of line-spectral frequencies - (LSFs) are obtained, quantized, and interpolated to obtain LSF - coefficients for each sub-block. Subsequently, the LPC residual is - computed by using the quantized and interpolated LPC analysis - filters. - - The two consecutive sub-blocks of the residual exhibiting the maximal - weighted energy are identified. Within these two sub-blocks, the - start state (segment) is selected from two choices: the first 57/58 - samples or the last 57/58 samples of the two consecutive sub-blocks. - The selected segment is the one of higher energy. The start state is - encoded with scalar quantization. - - A dynamic codebook encoding procedure is used to encode 1) the 23/22 - (20 ms/30 ms) remaining samples in the two sub-blocks containing the - start state; 2) the sub-blocks after the start state in time; and 3) - the sub-blocks before the start state in time. Thus, the encoding - target can be either the 23/22 samples remaining of the two sub- - blocks containing the start state or a 40-sample sub-block. This - target can consist of samples indexed forward in time or backward in - time, depending on the location of the start state. - - The codebook coding is based on an adaptive codebook built from a - codebook memory that contains decoded LPC excitation samples from the - already encoded part of the block. These samples are indexed in the - same time direction as the target vector, ending at the sample - instant prior to the first sample instant represented in the target - vector. The codebook is used in CB_NSTAGES=3 stages in a successive - refinement approach, and the resulting three code vector gains are - encoded with 5-, 4-, and 3-bit scalar quantization, respectively. - - The codebook search method employs noise shaping derived from the LPC - filters, and the main decision criterion is to minimize the squared - error between the target vector and the code vectors. Each code - vector in this codebook comes from one of CB_EXPAND=2 codebook - sections. The first section is filled with delayed, already encoded - residual vectors. The code vectors of the second codebook section - are constructed by predefined linear combinations of vectors in the - first section of the codebook. - - As codebook encoding with squared-error matching is known to produce - a coded signal of less power than does the scalar quantized start - state signal, a gain re-scaling method is implemented by a refined - search for a better set of codebook gains in terms of power matching - after encoding. This is done by searching for a higher value of the - gain factor for the first stage codebook, as the subsequent stage - codebook gains are scaled by the first stage gain. - - - - -Andersen, et al. Experimental [Page 6] - -RFC 3951 Internet Low Bit Rate Codec December 2004 - - -2.2. Decoder - - Typically for packet communications, a jitter buffer placed at the - receiving end decides whether the packet containing an encoded signal - block has been received or lost. This logic is not part of the codec - described here. For each encoded signal block received the decoder - performs a decoding. For each lost signal block, the decoder - performs a PLC operation. - - The decoding for each block starts by decoding and interpolating the - LPC coefficients. Subsequently the start state is decoded. - - For codebook-encoded segments, each segment is decoded by - constructing the three code vectors given by the received codebook - indices in the same way that the code vectors were constructed in the - encoder. The three gain factors are also decoded and the resulting - decoded signal is given by the sum of the three codebook vectors - scaled with respective gain. - - An enhancement algorithm is applied to the reconstructed excitation - signal. This enhancement augments the periodicity of voiced speech - regions. The enhancement is optimized under the constraint that the - modification signal (defined as the difference between the enhanced - excitation and the excitation signal prior to enhancement) has a - short-time energy that does not exceed a preset fraction of the - short-time energy of the excitation signal prior to enhancement. - - A packet loss concealment (PLC) operation is easily embedded in the - decoder. The PLC operation can, e.g., be based on repeating LPC - filters and obtaining the LPC residual signal by using a long-term - prediction estimate from previous residual blocks. - -3. Encoder Principles - - The following block diagram is an overview of all the components of - the iLBC encoding procedure. The description of the blocks contains - references to the section where that particular procedure is further - described. - - - - - - - - - - - - - -Andersen, et al. Experimental [Page 7] - -RFC 3951 Internet Low Bit Rate Codec December 2004 - - - +-----------+ +---------+ +---------+ - speech -> | 1. Pre P | -> | 2. LPC | -> | 3. Ana | -> - +-----------+ +---------+ +---------+ - - +---------------+ +--------------+ - -> | 4. Start Sel | ->| 5. Scalar Qu | -> - +---------------+ +--------------+ - - +--------------+ +---------------+ - -> |6. CB Search | -> | 7. Packetize | -> payload - | +--------------+ | +---------------+ - ----<---------<------ - sub-frame 0..2/4 (20 ms/30 ms) - - Figure 3.1. Flow chart of the iLBC encoder - - 1. Pre-process speech with a HP filter, if needed (section 3.1). - - 2. Compute LPC parameters, quantize, and interpolate (section 3.2). - - 3. Use analysis filters on speech to compute residual (section 3.3). - - 4. Select position of 57/58-sample start state (section 3.5). - - 5. Quantize the 57/58-sample start state with scalar quantization - (section 3.5). - - 6. Search the codebook for each sub-frame. Start with 23/22 sample - block, then encode sub-blocks forward in time, and then encode - sub-blocks backward in time. For each block, the steps in Figure - 3.4 are performed (section 3.6). - - 7. Packetize the bits into the payload specified in Table 3.2. - - The input to the encoder SHOULD be 16-bit uniform PCM sampled at 8 - kHz. Also it SHOULD be partitioned into blocks of BLOCKL=160/240 - samples. Each block input to the encoder is divided into NSUB=4/6 - consecutive sub-blocks of SUBL=40 samples each. - - - - - - - - - - - - - -Andersen, et al. Experimental [Page 8] - -RFC 3951 Internet Low Bit Rate Codec December 2004 - - - 0 39 79 119 159 - +---------------------------------------+ - | 1 | 2 | 3 | 4 | - +---------------------------------------+ - 20 ms frame - - 0 39 79 119 159 199 239 - +-----------------------------------------------------------+ - | 1 | 2 | 3 | 4 | 5 | 6 | - +-----------------------------------------------------------+ - 30 ms frame - Figure 3.2. One input block to the encoder for 20 ms (with four sub- - frames) and 30 ms (with six sub-frames). - -3.1. Pre-processing - - In some applications, the recorded speech signal contains DC level - and/or 50/60 Hz noise. If these components have not been removed - prior to the encoder call, they should be removed by a high-pass - filter. A reference implementation of this, using a filter with a - cutoff frequency of 90 Hz, can be found in Appendix A.28. - -3.2. LPC Analysis and Quantization - - The input to the LPC analysis module is a possibly high-pass filtered - speech buffer, speech_hp, that contains 240/300 (LPC_LOOKBACK + - BLOCKL = 80/60 + 160/240 = 240/300) speech samples, where samples 0 - through 79/59 are from the previous block and samples 80/60 through - 239/299 are from the current block. No look-ahead into the next - block is used. For the very first block processed, the look-back - samples are assumed to be zeros. - - For each input block, the LPC analysis calculates one/two set(s) of - LPC_FILTERORDER=10 LPC filter coefficients using the autocorrelation - method and the Levinson-Durbin recursion. These coefficients are - converted to the Line Spectrum Frequency representation. In the 20 - ms case, the single lsf set represents the spectral characteristics - as measured at the center of the third sub-block. For 30 ms frames, - the first set, lsf1, represents the spectral properties of the input - signal at the center of the second sub-block, and the other set, - lsf2, represents the spectral characteristics as measured at the - center of the fifth sub-block. The details of the computation for 30 - ms frames are described in sections 3.2.1 through 3.2.6. Section - 3.2.7 explains how the LPC Analysis and Quantization differs for 20 - ms frames. - - - - - - -Andersen, et al. Experimental [Page 9] - -RFC 3951 Internet Low Bit Rate Codec December 2004 - - -3.2.1. Computation of Autocorrelation Coefficients - - The first step in the LPC analysis procedure is to calculate - autocorrelation coefficients by using windowed speech samples. This - windowing is the only difference in the LPC analysis procedure for - the two sets of coefficients. For the first set, a 240-sample-long - standard symmetric Hanning window is applied to samples 0 through 239 - of the input data. The first window, lpc_winTbl, is defined as - - lpc_winTbl[i]= 0.5 * (1.0 - cos((2*PI*(i+1))/(BLOCKL+1))); - i=0,...,119 - lpc_winTbl[i] = winTbl[BLOCKL - i - 1]; i=120,...,239 - - The windowed speech speech_hp_win1 is then obtained by multiplying - the first 240 samples of the input speech buffer with the window - coefficients: - - speech_hp_win1[i] = speech_hp[i] * lpc_winTbl[i]; - i=0,...,BLOCKL-1 - - From these 240 windowed speech samples, 11 (LPC_FILTERORDER + 1) - autocorrelation coefficients, acf1, are calculated: - - acf1[lag] += speech_hp_win1[n] * speech_hp_win1[n + lag]; - lag=0,...,LPC_FILTERORDER; n=0,...,BLOCKL-lag-1 - - In order to make the analysis more robust against numerical precision - problems, a spectral smoothing procedure is applied by windowing the - autocorrelation coefficients before the LPC coefficients are - computed. Also, a white noise floor is added to the autocorrelation - function by multiplying coefficient zero by 1.0001 (40dB below the - energy of the windowed speech signal). These two steps are - implemented by multiplying the autocorrelation coefficients with the - following window: - - lpc_lagwinTbl[0] = 1.0001; - lpc_lagwinTbl[i] = exp(-0.5 * ((2 * PI * 60.0 * i) /FS)^2); - i=1,...,LPC_FILTERORDER - where FS=8000 is the sampling frequency - - Then, the windowed acf function acf1_win is obtained by - - acf1_win[i] = acf1[i] * lpc_lagwinTbl[i]; - i=0,...,LPC_FILTERORDER - - The second set of autocorrelation coefficients, acf2_win, are - obtained in a similar manner. The window, lpc_asymwinTbl, is applied - to samples 60 through 299, i.e., the entire current block. The - - - -Andersen, et al. Experimental [Page 10] - -RFC 3951 Internet Low Bit Rate Codec December 2004 - - - window consists of two segments, the first (samples 0 to 219) being - half a Hanning window with length 440 and the second a quarter of a - cycle of a cosine wave. By using this asymmetric window, an LPC - analysis centered in the fifth sub-block is obtained without the need - for any look-ahead, which would add delay. The asymmetric window is - defined as - - lpc_asymwinTbl[i] = (sin(PI * (i + 1) / 441))^2; i=0,...,219 - - lpc_asymwinTbl[i] = cos((i - 220) * PI / 40); i=220,...,239 - - and the windowed speech is computed by - - speech_hp_win2[i] = speech_hp[i + LPC_LOOKBACK] * - lpc_asymwinTbl[i]; i=0,....BLOCKL-1 - - The windowed autocorrelation coefficients are then obtained in - exactly the same way as for the first analysis instance. - - The generation of the windows lpc_winTbl, lpc_asymwinTbl, and - lpc_lagwinTbl are typically done in advance, and the arrays are - stored in ROM rather than repeating the calculation for every block. - -3.2.2. Computation of LPC Coefficients - - From the 2 x 11 smoothed autocorrelation coefficients, acf1_win and - acf2_win, the 2 x 11 LPC coefficients, lp1 and lp2, are calculated - in the same way for both analysis locations by using the well known - Levinson-Durbin recursion. The first LPC coefficient is always 1.0, - resulting in ten unique coefficients. - - After determining the LPC coefficients, a bandwidth expansion - procedure is applied to smooth the spectral peaks in the - short-term spectrum. The bandwidth addition is obtained by the - following modification of the LPC coefficients: - - lp1_bw[i] = lp1[i] * chirp^i; i=0,...,LPC_FILTERORDER - lp2_bw[i] = lp2[i] * chirp^i; i=0,...,LPC_FILTERORDER - - where "chirp" is a real number between 0 and 1. It is RECOMMENDED to - use a value of 0.9. - -3.2.3. Computation of LSF Coefficients from LPC Coefficients - - Thus far, two sets of LPC coefficients that represent the short-term - spectral characteristics of the speech signal for two different time - locations within the current block have been determined. These - coefficients SHOULD be quantized and interpolated. Before this is - - - -Andersen, et al. Experimental [Page 11] - -RFC 3951 Internet Low Bit Rate Codec December 2004 - - - done, it is advantageous to convert the LPC parameters into another - type of representation called Line Spectral Frequencies (LSF). The - LSF parameters are used because they are better suited for - quantization and interpolation than the regular LPC coefficients. - Many computationally efficient methods for calculating the LSFs from - the LPC coefficients have been proposed in the literature. The - detailed implementation of one applicable method can be found in - Appendix A.26. The two arrays of LSF coefficients obtained, lsf1 and - lsf2, are of dimension 10 (LPC_FILTERORDER). - -3.2.4. Quantization of LSF Coefficients - - Because the LPC filters defined by the two sets of LSFs are also - needed in the decoder, the LSF parameters need to be quantized and - transmitted as side information. The total number of bits required - to represent the quantization of the two LSF representations for one - block of speech is 40, with 20 bits used for each of lsf1 and lsf2. - - For computational and storage reasons, the LSF vectors are quantized - using three-split vector quantization (VQ). That is, the LSF vectors - are split into three sub-vectors that are each quantized with a - regular VQ. The quantized versions of lsf1 and lsf2, qlsf1 and - qlsf2, are obtained by using the same memoryless split VQ. The - length of each of these two LSF vectors is 10, and they are split - into three sub-vectors containing 3, 3, and 4 values, respectively. - - For each of the sub-vectors, a separate codebook of quantized values - has been designed with a standard VQ training method for a large - database containing speech from a large number of speakers recorded - under various conditions. The size of each of the three codebooks - associated with the split definitions above is - - int size_lsfCbTbl[LSF_NSPLIT] = {64,128,128}; - - The actual values of the vector quantization codebook that must be - used can be found in the reference code of Appendix A. Both sets of - LSF coefficients, lsf1 and lsf2, are quantized with a standard - memoryless split vector quantization (VQ) structure using the squared - error criterion in the LSF domain. The split VQ quantization - consists of the following steps: - - 1) Quantize the first three LSF coefficients (1 - 3) with a VQ - codebook of size 64. - 2) Quantize the next three LSF coefficients 4 - 6 with VQ a codebook - of size 128. - 3) Quantize the last four LSF coefficients (7 - 10) with a VQ - codebook of size 128. - - - - -Andersen, et al. Experimental [Page 12] - -RFC 3951 Internet Low Bit Rate Codec December 2004 - - - This procedure, repeated for lsf1 and lsf2, gives six quantization - indices and the quantized sets of LSF coefficients qlsf1 and qlsf2. - Each set of three indices is encoded with 6 + 7 + 7 = 20 bits. The - total number of bits used for LSF quantization in a block is thus 40 - bits. - -3.2.5. Stability Check of LSF Coefficients - - The LSF representation of the LPC filter has the convenient property - that the coefficients are ordered by increasing value, i.e., lsf(n-1) - < lsf(n), 0 < n < 10, if the corresponding synthesis filter is - stable. As we are employing a split VQ scheme, it is possible that - at the split boundaries the LSF coefficients are not ordered - correctly and hence that the corresponding LP filter is unstable. To - ensure that the filter used is stable, a stability check is performed - for the quantized LSF vectors. If it turns out that the coefficients - are not ordered appropriately (with a safety margin of 50 Hz to - ensure that formant peaks are not too narrow), they will be moved - apart. The detailed method for this can be found in Appendix A.40. - The same procedure is performed in the decoder. This ensures that - exactly the same LSF representations are used in both encoder and - decoder. - -3.2.6. Interpolation of LSF Coefficients - - From the two sets of LSF coefficients that are computed for each - block of speech, different LSFs are obtained for each sub-block by - means of interpolation. This procedure is performed for the original - LSFs (lsf1 and lsf2), as well as the quantized versions qlsf1 and - qlsf2, as both versions are used in the encoder. Here follows a - brief summary of the interpolation scheme; the details are found in - the c-code of Appendix A. In the first sub-block, the average of the - second LSF vector from the previous block and the first LSF vector in - the current block is used. For sub-blocks two through five, the LSFs - used are obtained by linear interpolation from lsf1 (and qlsf1) to - lsf2 (and qlsf2), with lsf1 used in sub-block two and lsf2 in sub- - block five. In the last sub-block, lsf2 is used. For the very first - block it is assumed that the last LSF vector of the previous block is - equal to a predefined vector, lsfmeanTbl, obtained by calculating the - mean LSF vector of the LSF design database. - - lsfmeanTbl[LPC_FILTERORDER] = {0.281738, 0.445801, 0.663330, - 0.962524, 1.251831, 1.533081, 1.850586, 2.137817, - 2.481445, 2.777344} - - - - - - - -Andersen, et al. Experimental [Page 13] - -RFC 3951 Internet Low Bit Rate Codec December 2004 - - - The interpolation method is standard linear interpolation in the LSF - domain. The interpolated LSF values are converted to LPC - coefficients for each sub-block. The unquantized and quantized LPC - coefficients form two sets of filters respectively. The unquantized - analysis filter for sub-block k is defined as follows - - ___ - \ - Ak(z)= 1 + > ak(i)*z^(-i) - /__ - i=1...LPC_FILTERORDER - - The quantized analysis filter for sub-block k is defined as follows - ___ - \ - A~k(z)= 1 + > a~k(i)*z^(-i) - /__ - i=1...LPC_FILTERORDER - - A reference implementation of the lsf encoding is given in Appendix - A.38. A reference implementation of the corresponding decoding can - be found in Appendix A.36. - -3.2.7. LPC Analysis and Quantization for 20 ms Frames - - As previously stated, the codec only calculates one set of LPC - parameters for the 20 ms frame size as opposed to two sets for 30 ms - frames. A single set of autocorrelation coefficients is calculated - on the LPC_LOOKBACK + BLOCKL = 80 + 160 = 240 samples. These samples - are windowed with the asymmetric window lpc_asymwinTbl, centered over - the third sub-frame, to form speech_hp_win. Autocorrelation - coefficients, acf, are calculated on the 240 samples in speech_hp_win - and then windowed exactly as in section 3.2.1 (resulting in - acf_win). - - This single set of windowed autocorrelation coefficients is used to - calculate LPC coefficients, LSF coefficients, and quantized LSF - coefficients in exactly the same manner as in sections 3.2.3 through - 3.2.4. As for the 30 ms frame size, the ten LSF coefficients are - divided into three sub-vectors of size 3, 3, and 4 and quantized by - using the same scheme and codebook as in section 3.2.4 to finally get - 3 quantization indices. The quantized LSF coefficients are - stabilized with the algorithm described in section 3.2.5. - - From the set of LSF coefficients computed for this block and those - from the previous block, different LSFs are obtained for each sub- - block by means of interpolation. The interpolation is done linearly - in the LSF domain over the four sub-blocks, so that the n-th sub- - - - -Andersen, et al. Experimental [Page 14] - -RFC 3951 Internet Low Bit Rate Codec December 2004 - - - frame uses the weight (4-n)/4 for the LSF from old frame and the - weight n/4 of the LSF from the current frame. For the very first - block the mean LSF, lsfmeanTbl, is used as the LSF from the previous - block. Similarly as seen in section 3.2.6, both unquantized, A(z), - and quantized, A~(z), analysis filters are calculated for each of the - four sub-blocks. - -3.3. Calculation of the Residual - - The block of speech samples is filtered by the quantized and - interpolated LPC analysis filters to yield the residual signal. In - particular, the corresponding LPC analysis filter for each 40 sample - sub-block is used to filter the speech samples for the same sub- - block. The filter memory at the end of each sub-block is carried - over to the LPC filter of the next sub-block. The signal at the - output of each LP analysis filter constitutes the residual signal for - the corresponding sub-block. - - A reference implementation of the LPC analysis filters is given in - Appendix A.10. - -3.4. Perceptual Weighting Filter - - In principle any good design of a perceptual weighting filter can be - applied in the encoder without compromising this codec definition. - However, it is RECOMMENDED to use the perceptual weighting filter Wk - for sub-block k specified below: - - Wk(z)=1/Ak(z/LPC_CHIRP_WEIGHTDENUM), where - LPC_CHIRP_WEIGHTDENUM = 0.4222 - - This is a simple design with low complexity that is applied in the - LPC residual domain. Here Ak(z) is the filter obtained for sub-block - k from unquantized but interpolated LSF coefficients. - -3.5. Start State Encoder - - The start state is quantized by using a common 6-bit scalar quantizer - for the block and a 3-bit scalar quantizer operating on scaled - samples in the weighted speech domain. In the following we describe - the state encoding in greater detail. - - - - - - - - - - -Andersen, et al. Experimental [Page 15] - -RFC 3951 Internet Low Bit Rate Codec December 2004 - - -3.5.1. Start State Estimation - - The two sub-blocks containing the start state are determined by - finding the two consecutive sub-blocks in the block having the - highest power. Advantageously, down-weighting is used in the - beginning and end of the sub-frames, i.e., the following measure is - computed (NSUB=4/6 for 20/30 ms frame size): - - nsub=1,...,NSUB-1 - ssqn[nsub] = 0.0; - for (i=(nsub-1)*SUBL; i<(nsub-1)*SUBL+5; i++) - ssqn[nsub] += sampEn_win[i-(nsub-1)*SUBL]* - residual[i]*residual[i]; - for (i=(nsub-1)*SUBL+5; i<(nsub+1)*SUBL-5; i++) - ssqn[nsub] += residual[i]*residual[i]; - for (i=(nsub+1)*SUBL-5; i<(nsub+1)*SUBL; i++) - ssqn[nsub] += sampEn_win[(nsub+1)*SUBL-i-1]* - residual[i]*residual[i]; - - where sampEn_win[5]={1/6, 2/6, 3/6, 4/6, 5/6}; MAY be used. The - sub-frame number corresponding to the maximum value of - ssqEn_win[nsub-1]*ssqn[nsub] is selected as the start state - indicator. A weighting of ssqEn_win[]={0.8,0.9,1.0,0.9,0.8} for 30 - ms frames and ssqEn_win[]={0.9,1.0,0.9} for 20 ms frames; MAY - advantageously be used to bias the start state towards the middle of - the frame. - - For 20 ms frames there are three possible positions for the two-sub- - block length maximum power segment; the start state position is - encoded with 2 bits. The start state position, start, MUST be - encoded as - - start=1: start state in sub-frame 0 and 1 - start=2: start state in sub-frame 1 and 2 - start=3: start state in sub-frame 2 and 3 - - For 30 ms frames there are five possible positions of the two-sub- - block length maximum power segment, the start state position is - encoded with 3 bits. The start state position, start, MUST be - encoded as - - start=1: start state in sub-frame 0 and 1 - start=2: start state in sub-frame 1 and 2 - start=3: start state in sub-frame 2 and 3 - start=4: start state in sub-frame 3 and 4 - start=5: start state in sub-frame 4 and 5 - - - - - -Andersen, et al. Experimental [Page 16] - -RFC 3951 Internet Low Bit Rate Codec December 2004 - - - Hence, in both cases, index 0 is not used. In order to shorten the - start state for bit rate efficiency, the start state is brought down - to STATE_SHORT_LEN=57 samples for 20 ms frames and STATE_SHORT_LEN=58 - samples for 30 ms frames. The power of the first 23/22 and last - 23/22 samples of the two sub-frame blocks identified above is - computed as the sum of the squared signal sample values, and the - 23/22-sample segment with the lowest power is excluded from the start - state. One bit is transmitted to indicate which of the two possible - 57/58 sample segments is used. The start state position within the - two sub-frames determined above, state_first, MUST be encoded as - - state_first=1: start state is first STATE_SHORT_LEN samples - state_first=0: start state is last STATE_SHORT_LEN samples - -3.5.2. All-Pass Filtering and Scale Quantization - - The block of residual samples in the start state is first filtered by - an all-pass filter with the quantized LPC coefficients as denominator - and reversed quantized LPC coefficients as numerator. The purpose of - this phase-dispersion filter is to get a more even distribution of - the sample values in the residual signal. The filtering is performed - by circular convolution, where the initial filter memory is set to - zero. - - res(0..(STATE_SHORT_LEN-1)) = uncoded start state residual - res((STATE_SHORT_LEN)..(2*STATE_SHORT_LEN-1)) = 0 - - Pk(z) = A~rk(z)/A~k(z), where - ___ - \ - A~rk(z)= z^(-LPC_FILTERORDER)+>a~k(i+1)*z^(i-(LPC_FILTERORDER-1)) - /__ - i=0...(LPC_FILTERORDER-1) - - and A~k(z) is taken from the block where the start state begins - - res -> Pk(z) -> filtered - - ccres(k) = filtered(k) + filtered(k+STATE_SHORT_LEN), - k=0..(STATE_SHORT_LEN-1) - - The all-pass filtered block is searched for its largest magnitude - sample. The 10-logarithm of this magnitude is quantized with a 6-bit - quantizer, state_frgqTbl, by finding the nearest representation. - - - - - - - -Andersen, et al. Experimental [Page 17] - -RFC 3951 Internet Low Bit Rate Codec December 2004 - - - This results in an index, idxForMax, corresponding to a quantized - value, qmax. The all-pass filtered residual samples in the block are - then multiplied with a scaling factor scal=4.5/(10^qmax) to yield - normalized samples. - - state_frgqTbl[64] = {1.000085, 1.071695, 1.140395, 1.206868, - 1.277188, 1.351503, 1.429380, 1.500727, 1.569049, - 1.639599, 1.707071, 1.781531, 1.840799, 1.901550, - 1.956695, 2.006750, 2.055474, 2.102787, 2.142819, - 2.183592, 2.217962, 2.257177, 2.295739, 2.332967, - 2.369248, 2.402792, 2.435080, 2.468598, 2.503394, - 2.539284, 2.572944, 2.605036, 2.636331, 2.668939, - 2.698780, 2.729101, 2.759786, 2.789834, 2.818679, - 2.848074, 2.877470, 2.906899, 2.936655, 2.967804, - 3.000115, 3.033367, 3.066355, 3.104231, 3.141499, - 3.183012, 3.222952, 3.265433, 3.308441, 3.350823, - 3.395275, 3.442793, 3.490801, 3.542514, 3.604064, - 3.666050, 3.740994, 3.830749, 3.938770, 4.101764} - -3.5.3. Scalar Quantization - - The normalized samples are quantized in the perceptually weighted - speech domain by a sample-by-sample scalar DPCM quantization as - depicted in Figure 3.3. Each sample in the block is filtered by a - weighting filter Wk(z), specified in section 3.4, to form a weighted - speech sample x[n]. The target sample d[n] is formed by subtracting - a predicted sample y[n], where the prediction filter is given by - - Pk(z) = 1 - 1 / Wk(z). - - +-------+ x[n] + d[n] +-----------+ u[n] - residual -->| Wk(z) |-------->(+)---->| Quantizer |------> quantized - +-------+ - /|\ +-----------+ | residual - | \|/ - y[n] +--------------------->(+) - | | - | +------+ | - +--------| Pk(z)|<------+ - +------+ - - Figure 3.3. Quantization of start state samples by DPCM in weighted - speech domain. - - The coded state sample u[n] is obtained by quantizing d[n] with a 3- - bit quantizer with quantization table state_sq3Tbl. - - state_sq3Tbl[8] = {-3.719849, -2.177490, -1.130005, -0.309692, - 0.444214, 1.329712, 2.436279, 3.983887} - - - -Andersen, et al. Experimental [Page 18] - -RFC 3951 Internet Low Bit Rate Codec December 2004 - - - The quantized samples are transformed back to the residual domain by - 1) scaling with 1/scal; 2) time-reversing the scaled samples; 3) - filtering the time-reversed samples by the same all-pass filter, as - in section 3.5.2, by using circular convolution; and 4) time- - reversing the filtered samples. (More detail is in section 4.2.) - - A reference implementation of the start-state encoding can be found - in Appendix A.46. - -3.6. Encoding the Remaining Samples - - A dynamic codebook is used to encode 1) the 23/22 remaining samples - in the two sub-blocks containing the start state; 2) the sub-blocks - after the start state in time; and 3) the sub-blocks before the start - state in time. Thus, the encoding target can be either the 23/22 - samples remaining of the 2 sub-blocks containing the start state, or - a 40-sample sub-block. This target can consist of samples that are - indexed forward in time or backward in time, depending on the - location of the start state. The length of the target is denoted by - lTarget. - - The coding is based on an adaptive codebook that is built from a - codebook memory that contains decoded LPC excitation samples from the - already encoded part of the block. These samples are indexed in the - same time direction as is the target vector and end at the sample - instant prior to the first sample instant represented in the target - vector. The codebook memory has length lMem, which is equal to - CB_MEML=147 for the two/four 40-sample sub-blocks and 85 for the - 23/22-sample sub-block. - - The following figure shows an overview of the encoding procedure. - - +------------+ +---------------+ +-------------+ - -> | 1. Decode | -> | 2. Mem setup | -> | 3. Perc. W. | -> - +------------+ +---------------+ +-------------+ - - +------------+ +-----------------+ - -> | 4. Search | -> | 5. Upd. Target | ------------------> - | +------------+ +------------------ | - ----<-------------<-----------<---------- - stage=0..2 - - +----------------+ - -> | 6. Recalc G[0] | ---------------> gains and CB indices - +----------------+ - - Figure 3.4. Flow chart of the codebook search in the iLBC encoder. - - - - -Andersen, et al. Experimental [Page 19] - -RFC 3951 Internet Low Bit Rate Codec December 2004 - - - 1. Decode the part of the residual that has been encoded so far, - using the codebook without perceptual weighting. - - 2. Set up the memory by taking data from the decoded residual. This - memory is used to construct codebooks. For blocks preceding the - start state, both the decoded residual and the target are time - reversed (section 3.6.1). - 3. Filter the memory + target with the perceptual weighting filter - (section 3.6.2). - - 4. Search for the best match between the target and the codebook - vector. Compute the optimal gain for this match and quantize that - gain (section 3.6.4). - - 5. Update the perceptually weighted target by subtracting the - contribution from the selected codebook vector from the - perceptually weighted memory (quantized gain times selected - vector). Repeat 4 and 5 for the two additional stages. - - 6. Calculate the energy loss due to encoding of the residual. If - needed, compensate for this loss by an upscaling and - requantization of the gain for the first stage (section 3.7). - - The following sections provide an in-depth description of the - different blocks of Figure 3.4. - -3.6.1. Codebook Memory - - The codebook memory is based on the already encoded sub-blocks, so - the available data for encoding increases for each new sub-block that - has been encoded. Until enough sub-blocks have been encoded to fill - the codebook memory with data, it is padded with zeros. The - following figure shows an example of the order in which the sub- - blocks are encoded for the 30 ms frame size if the start state is - located in the last 58 samples of sub-block 2 and 3. - - +-----------------------------------------------------+ - | 5 | 1 |///|////////| 2 | 3 | 4 | - +-----------------------------------------------------+ - - Figure 3.5. The order from 1 to 5 in which the sub-blocks are - encoded. The slashed area is the start state. - - - - - - - - - -Andersen, et al. Experimental [Page 20] - -RFC 3951 Internet Low Bit Rate Codec December 2004 - - - The first target sub-block to be encoded is number 1, and the - corresponding codebook memory is shown in the following figure. As - the target vector comes before the start state in time, the codebook - memory and target vector are time reversed; thus, after the block has - been time reversed the search algorithm can be reused. As only the - start state has been encoded so far, the last samples of the codebook - memory are padded with zeros. - - +------------------------- - |zeros|\\\\\\\\|\\\\| 1 | - +------------------------- - - Figure 3.6. The codebook memory, length lMem=85 samples, and the - target vector 1, length 22 samples. - - The next step is to encode sub-block 2 by using the memory that now - has increased since sub-block 1 has been encoded. The following - figure shows the codebook memory for encoding of sub-block 2. - - +----------------------------------- - | zeros | 1 |///|////////| 2 | - +----------------------------------- - - Figure 3.7. The codebook memory, length lMem=147 samples, and the - target vector 2, length 40 samples. - - The next step is to encode sub-block 3 by using the memory which has - been increased yet again since sub-blocks 1 and 2 have been encoded, - but the sub-block still has to be padded with a few zeros. The - following figure shows the codebook memory for encoding of sub-block - 3. - - +------------------------------------------ - |zeros| 1 |///|////////| 2 | 3 | - +------------------------------------------ - - Figure 3.8. The codebook memory, length lMem=147 samples, and the - target vector 3, length 40 samples. - - The next step is to encode sub-block 4 by using the memory which now - has increased yet again since sub-blocks 1, 2, and 3 have been - encoded. This time, the memory does not have to be padded with - zeros. The following figure shows the codebook memory for encoding - of sub-block 4. - - - - - - - -Andersen, et al. Experimental [Page 21] - -RFC 3951 Internet Low Bit Rate Codec December 2004 - - - +------------------------------------------ - |1|///|////////| 2 | 3 | 4 | - +------------------------------------------ - - Figure 3.9. The codebook memory, length lMem=147 samples, and the - target vector 4, length 40 samples. - - The final target sub-block to be encoded is number 5, and the - following figure shows the corresponding codebook memory. As the - target vector comes before the start state in time, the codebook - memory and target vector are time reversed. - - +------------------------------------------- - | 3 | 2 |\\\\\\\\|\\\\| 1 | 5 | - +------------------------------------------- - - Figure 3.10. The codebook memory, length lMem=147 samples, and the - target vector 5, length 40 samples. - - For the case of 20 ms frames, the encoding procedure looks almost - exactly the same. The only difference is that the size of the start - state is 57 samples and that there are only three sub-blocks to be - encoded. The encoding order is the same as above, starting with the - 23-sample target and then encoding the two remaining 40-sample sub- - blocks, first going forward in time and then going backward in time - relative to the start state. - -3.6.2. Perceptual Weighting of Codebook Memory and Target - - To provide a perceptual weighting of the coding error, a - concatenation of the codebook memory and the target to be coded is - all-pole filtered with the perceptual weighting filter specified in - section 3.4. The filter state of the weighting filter is set to - zero. - - in(0..(lMem-1)) = unweighted codebook memory - in(lMem..(lMem+lTarget-1)) = unweighted target signal - - - in -> Wk(z) -> filtered, - where Wk(z) is taken from the sub-block of the target - - weighted codebook memory = filtered(0..(lMem-1)) - weighted target signal = filtered(lMem..(lMem+lTarget-1)) - - The codebook search is done with the weighted codebook memory and the - weighted target, whereas the decoding and the codebook memory update - uses the unweighted codebook memory. - - - -Andersen, et al. Experimental [Page 22] - -RFC 3951 Internet Low Bit Rate Codec December 2004 - - -3.6.3. Codebook Creation - - The codebook for the search is created from the perceptually weighted - codebook memory. It consists of two sections, where the first is - referred to as the base codebook and the second as the expanded - codebook, as it is created by linear combinations of the first. Each - of these two sections also has a subsection referred to as the - augmented codebook. The augmented codebook is only created and used - for the coding of the 40-sample sub-blocks and not for the 23/22- - sample sub-block case. The codebook size used for the different - sub-blocks and different stages are summarized in the table below. - - Stage - 1 2 & 3 - -------------------------------------------- - 22 128 (64+0)*2 128 (64+0)*2 - Sub- 1:st 40 256 (108+20)*2 128 (44+20)*2 - Blocks 2:nd 40 256 (108+20)*2 256 (108+20)*2 - 3:rd 40 256 (108+20)*2 256 (108+20)*2 - 4:th 40 256 (108+20)*2 256 (108+20)*2 - - Table 3.1. Codebook sizes for the 30 ms mode. - - Table 3.1 shows the codebook size for the different sub-blocks and - stages for 30 ms frames. Inside the parentheses it shows how the - number of codebook vectors is distributed, within the two sections, - between the base/expanded codebook and the augmented base/expanded - codebook. It should be interpreted in the following way: - (base/expanded cb + augmented base/expanded cb). The total number of - codebook vectors for a specific sub-block and stage is given by the - following formula: - - Tot. cb vectors = base cb + aug. base cb + exp. cb + aug. exp. cb - - The corresponding values to Figure 3.1 for 20 ms frames are only - slightly modified. The short sub-block is 23 instead of 22 samples, - and the 3:rd and 4:th sub-frame are not present. - -3.6.3.1. Creation of a Base Codebook - - The base codebook is given by the perceptually weighted codebook - memory that is mentioned in section 3.5.3. The different codebook - vectors are given by sliding a window of length 23/22 or 40, given by - variable lTarget, over the lMem-long perceptually weighted codebook - memory. The indices are ordered so that the codebook vector - containing sample (lMem-lTarget-n) to (lMem-n-1) of the codebook - - - - - -Andersen, et al. Experimental [Page 23] - -RFC 3951 Internet Low Bit Rate Codec December 2004 - - - memory vector has index n, where n=0..lMem-lTarget. Thus the total - number of base codebook vectors is lMem-lTarget+1, and the indices - are ordered from sample delay lTarget (23/22 or 40) to lMem+1 (86 or - 148). - -3.6.3.2. Codebook Expansion - - The base codebook is expanded by a factor of 2, creating an - additional section in the codebook. This new section is obtained by - filtering the base codebook, base_cb, with a FIR filter with filter - length CB_FILTERLEN=8. The construction of the expanded codebook - compensates for the delay of four samples introduced by the FIR - filter. - - cbfiltersTbl[CB_FILTERLEN]={-0.033691, 0.083740, -0.144043, - 0.713379, 0.806152, -0.184326, - 0.108887, -0.034180}; - - ___ - \ - exp_cb(k)= + > cbfiltersTbl(i)*x(k-i+4) - /__ - i=0...(LPC_FILTERORDER-1) - - where x(j) = base_cb(j) for j=0..lMem-1 and 0 otherwise - - The individual codebook vectors of the new filtered codebook, exp_cb, - and their indices are obtained in the same fashion as described above - for the base codebook. - -3.6.3.3. Codebook Augmentation - - For cases where encoding entire sub-blocks, i.e., cbveclen=40, the - base and expanded codebooks are augmented to increase codebook - richness. The codebooks are augmented by vectors produced by - interpolation of segments. The base and expanded codebook, - constructed above, consists of vectors corresponding to sample delays - in the range from cbveclen to lMem. The codebook augmentation - attempts to augment these codebooks with vectors corresponding to - sample delays from 20 to 39. However, not all of these samples are - present in the base codebook and expanded codebook, respectively. - Therefore, the augmentation vectors are constructed as linear - combinations between samples corresponding to sample delays in the - range 20 to 39. The general idea of this procedure is presented in - the following figures and text. The procedure is performed for both - the base codebook and the expanded codebook. - - - - - -Andersen, et al. Experimental [Page 24] - -RFC 3951 Internet Low Bit Rate Codec December 2004 - - - - - ------------------------| - codebook memory | - - - ------------------------| - |-5-|---15---|-5-| - pi pp po - - | | Codebook vector - |---15---|-5-|-----20-----| <- corresponding to - i ii iii sample delay 20 - - Figure 3.11. Generation of the first augmented codebook. - - Figure 3.11 shows the codebook memory with pointers pi, pp, and po, - where pi points to sample 25, pp to sample 20, and po to sample 5. - Below the codebook memory, the augmented codebook vector - corresponding to sample delay 20 is drawn. Segment i consists of - fifteen samples from pointer pp and forward in time. Segment ii - consists of five interpolated samples from pi and forward and from po - and forward. The samples are linearly interpolated with weights - [0.0, 0.2, 0.4, 0.6, 0.8] for pi and weights [1.0, 0.8, 0.6, 0.4, - 0.2] for po. Segment iii consists of twenty samples from pp and - forward. The augmented codebook vector corresponding to sample delay - 21 is produced by moving pointers pp and pi one sample backward in - time. This gives us the following figure. - - - - ------------------------| - codebook memory | - - - ------------------------| - |-5-|---16---|-5-| - pi pp po - - | | Codebook vector - |---16---|-5-|-----19-----| <- corresponding to - i ii iii sample delay 21 - - Figure 3.12. Generation of the second augmented codebook. - - Figure 3.12 shows the codebook memory with pointers pi, pp and po - where pi points to sample 26, pp to sample 21, and po to sample 5. - Below the codebook memory, the augmented codebook vector - corresponding to sample delay 21 is drawn. Segment i now consists of - sixteen samples from pp and forward. Segment ii consists of five - interpolated samples from pi and forward and from po and forward, and - the interpolation weights are the same throughout the procedure. - Segment iii consists of nineteen samples from pp and forward. The - same procedure of moving the two pointers is continued until the last - augmented vector corresponding to sample delay 39 has been created. - This gives a total of twenty new codebook vectors to each of the two - - - -Andersen, et al. Experimental [Page 25] - -RFC 3951 Internet Low Bit Rate Codec December 2004 - - - sections. Thus the total number of codebook vectors for each of the - two sections, when including the augmented codebook, becomes lMem- - SUBL+1+SUBL/2. This is provided that augmentation is evoked, i.e., - that lTarget=SUBL. - -3.6.4. Codebook Search - - The codebook search uses the codebooks described in the sections - above to find the best match of the perceptually weighted target, see - section 3.6.2. The search method is a multi-stage gain-shape - matching performed as follows. At each stage the best shape vector - is identified, then the gain is calculated and quantized, and finally - the target is updated in preparation for the next codebook search - stage. The number of stages is CB_NSTAGES=3. - - If the target is the 23/22-sample vector the codebooks are indexed so - that the base codebook is followed by the expanded codebook. If the - target is 40 samples the order is as follows: base codebook, - augmented base codebook, expanded codebook, and augmented expanded - codebook. The size of each codebook section and its corresponding - augmented section is given by Table 3.1 in section 3.6.3. - - For example, when the second 40-sample sub-block is coded, indices 0 - - 107 correspond to the base codebook, 108 - 127 correspond to the - augmented base codebook, 128 - 235 correspond to the expanded - codebook, and indices 236 - 255 correspond to the augmented expanded - codebook. The indices are divided in the same fashion for all stages - in the example. Only in the case of coding the first 40-sample sub- - block is there a difference between stages (see Table 3.1). - -3.6.4.1. Codebook Search at Each Stage - - The codebooks are searched to find the best match to the target at - each stage. When the best match is found, the target is updated and - the next-stage search is started. The three chosen codebook vectors - and their corresponding gains constitute the encoded sub-block. The - best match is decided by the following three criteria: - - 1. Compute the measure - - (target*cbvec)^2 / ||cbvec||^2 - - for all codebook vectors, cbvec, and choose the codebook vector - maximizing the measure. The expression (target*cbvec) is the dot - product between the target vector to be coded and the codebook vector - for which we compute the measure. The norm, ||x||, is defined as the - square root of (x*x). - - - - -Andersen, et al. Experimental [Page 26] - -RFC 3951 Internet Low Bit Rate Codec December 2004 - - - 2. The absolute value of the gain, corresponding to the chosen - codebook vector, cbvec, must be smaller than a fixed limit, - CB_MAXGAIN=1.3: - - |gain| < CB_MAXGAIN - - where the gain is computed in the following way: - - gain = (target*cbvec) / ||cbvec||^2 - - 3. For the first stage, the dot product of the chosen codebook vector - and target must be positive: - - target*cbvec > 0 - - In practice the above criteria are used in a sequential search - through all codebook vectors. The best match is found by registering - a new max measure and index whenever the previously registered max - measure is surpassed and all other criteria are fulfilled. If none - of the codebook vectors fulfill (2) and (3), the first codebook - vector is selected. - -3.6.4.2. Gain Quantization at Each Stage - - The gain follows as a result of the computation - - gain = (target*cbvec) / ||cbvec||^2 - - for the optimal codebook vector found by the procedure in section - 3.6.4.1. - - The three stages quantize the gain, using 5, 4, and 3 bits, - respectively. In the first stage, the gain is limited to positive - values. This gain is quantized by finding the nearest value in the - quantization table gain_sq5Tbl. - - gain_sq5Tbl[32]={0.037476, 0.075012, 0.112488, 0.150024, 0.187500, - 0.224976, 0.262512, 0.299988, 0.337524, 0.375000, - 0.412476, 0.450012, 0.487488, 0.525024, 0.562500, - 0.599976, 0.637512, 0.674988, 0.712524, 0.750000, - 0.787476, 0.825012, 0.862488, 0.900024, 0.937500, - 0.974976, 1.012512, 1.049988, 1.087524, 1.125000, - 1.162476, 1.200012} - - The gains of the subsequent two stages can be either positive or - negative. The gains are quantized by using a quantization table - times a scale factor. The second stage uses the table gain_sq4Tbl, - and the third stage uses gain_sq3Tbl. The scale factor equates 0.1 - - - -Andersen, et al. Experimental [Page 27] - -RFC 3951 Internet Low Bit Rate Codec December 2004 - - - or the absolute value of the quantized gain representation value - obtained in the previous stage, whichever is larger. Again, the - resulting gain index is the index to the nearest value of the - quantization table times the scale factor. - - gainQ = scaleFact * gain_sqXTbl[index] - - gain_sq4Tbl[16]={-1.049988, -0.900024, -0.750000, -0.599976, - -0.450012, -0.299988, -0.150024, 0.000000, 0.150024, - 0.299988, 0.450012, 0.599976, 0.750000, 0.900024, - 1.049988, 1.200012} - - gain_sq3Tbl[8]={-1.000000, -0.659973, -0.330017,0.000000, - 0.250000, 0.500000, 0.750000, 1.00000} - -3.6.4.3. Preparation of Target for Next Stage - - Before performing the search for the next stage, the perceptually - weighted target vector is updated by subtracting from it the selected - codebook vector (from the perceptually weighted codebook) times the - corresponding quantized gain. - - target[i] = target[i] - gainQ * selected_vec[i]; - - A reference implementation of the codebook encoding is found in - Appendix A.34. - -3.7. Gain Correction Encoding - - The start state is quantized in a relatively model independent manner - using 3 bits per sample. In contrast, the remaining parts of the - block are encoded by using an adaptive codebook. This codebook will - produce high matching accuracy whenever there is a high correlation - between the target and the best codebook vector. For unvoiced speech - segments and background noises, this is not necessarily so, which, - due to the nature of the squared error criterion, results in a coded - signal with less power than the target signal. As the coded start - state has good power matching to the target, the result is a power - fluctuation within the encoded frame. Perceptually, the main problem - with this is that the time envelope of the signal energy becomes - unsteady. To overcome this problem, the gains for the codebooks are - re-scaled after the codebook encoding by searching for a new gain - factor for the first stage codebook that provides better power - matching. - - First, the energy for the target signal, tene, is computed along with - the energy for the coded signal, cene, given by the addition of the - three gain scaled codebook vectors. Because the gains of the second - - - -Andersen, et al. Experimental [Page 28] - -RFC 3951 Internet Low Bit Rate Codec December 2004 - - - and third stage scale with the gain of the first stage, when the - first stage gain is changed from gain[0] to gain_sq5Tbl[i] the energy - of the coded signal changes from cene to - - cene*(gain_sq5Tbl[i]*gain_sq5Tbl[i])/(gain[0]*gain[0]) - - where gain[0] is the gain for the first stage found in the original - codebook search. A refined search is performed by testing the gain - indices i=0 to 31, and as long as the new codebook energy as given - above is less than tene, the gain index for stage 1 is increased. A - restriction is applied so that the new gain value for stage 1 cannot - be more than two times higher than the original value found in the - codebook search. Note that by using this method we do not change the - shape of the encoded vector, only the gain or amplitude. - -3.8. Bitstream Definition - - The total number of bits used to describe one frame of 20 ms speech - is 304, which fits in 38 bytes and results in a bit rate of 15.20 - kbit/s. For the case of a frame length of 30 ms speech, the total - number of bits used is 400, which fits in 50 bytes and results in a - bit rate of 13.33 kbit/s. In the bitstream definition, the bits are - distributed into three classes according to their bit error or loss - sensitivity. The most sensitive bits (class 1) are placed first in - the bitstream for each frame. The less sensitive bits (class 2) are - placed after the class 1 bits. The least sensitive bits (class 3) - are placed at the end of the bitstream for each frame. - - In the 20/30 ms frame length cases for each class, the following hold - true: The class 1 bits occupy a total of 6/8 bytes (48/64 bits), the - class 2 bits occupy 8/12 bytes (64/96 bits), and the class 3 bits - occupy 24/30 bytes (191/239 bits). This distribution of the bits - enables the use of uneven level protection (ULP) as is exploited in - the payload format definition for iLBC [1]. The detailed bit - allocation is shown in the table below. When a quantization index is - distributed between more classes, the more significant bits belong to - the lowest class. - - - - - - - - - - - - - - -Andersen, et al. Experimental [Page 29] - -RFC 3951 Internet Low Bit Rate Codec December 2004 - - - Bitstream structure: - - ------------------------------------------------------------------+ - Parameter | Bits Class <1,2,3> | - | 20 ms frame | 30 ms frame | - ----------------------------------+---------------+---------------+ - Split 1 | 6 <6,0,0> | 6 <6,0,0> | - LSF 1 Split 2 | 7 <7,0,0> | 7 <7,0,0> | - LSF Split 3 | 7 <7,0,0> | 7 <7,0,0> | - ------------------+---------------+---------------+ - Split 1 | NA (Not Appl.)| 6 <6,0,0> | - LSF 2 Split 2 | NA | 7 <7,0,0> | - Split 3 | NA | 7 <7,0,0> | - ------------------+---------------+---------------+ - Sum | 20 <20,0,0> | 40 <40,0,0> | - ----------------------------------+---------------+---------------+ - Block Class | 2 <2,0,0> | 3 <3,0,0> | - ----------------------------------+---------------+---------------+ - Position 22 sample segment | 1 <1,0,0> | 1 <1,0,0> | - ----------------------------------+---------------+---------------+ - Scale Factor State Coder | 6 <6,0,0> | 6 <6,0,0> | - ----------------------------------+---------------+---------------+ - Sample 0 | 3 <0,1,2> | 3 <0,1,2> | - Quantized Sample 1 | 3 <0,1,2> | 3 <0,1,2> | - Residual : | : : | : : | - State : | : : | : : | - Samples : | : : | : : | - Sample 56 | 3 <0,1,2> | 3 <0,1,2> | - Sample 57 | NA | 3 <0,1,2> | - ------------------+---------------+---------------+ - Sum | 171 <0,57,114>| 174 <0,58,116>| - ----------------------------------+---------------+---------------+ - Stage 1 | 7 <6,0,1> | 7 <4,2,1> | - CB for 22/23 Stage 2 | 7 <0,0,7> | 7 <0,0,7> | - sample block Stage 3 | 7 <0,0,7> | 7 <0,0,7> | - ------------------+---------------+---------------+ - Sum | 21 <6,0,15> | 21 <4,2,15> | - ----------------------------------+---------------+---------------+ - Stage 1 | 5 <2,0,3> | 5 <1,1,3> | - Gain for 22/23 Stage 2 | 4 <1,1,2> | 4 <1,1,2> | - sample block Stage 3 | 3 <0,0,3> | 3 <0,0,3> | - ------------------+---------------+---------------+ - Sum | 12 <3,1,8> | 12 <2,2,8> | - ----------------------------------+---------------+---------------+ - Stage 1 | 8 <7,0,1> | 8 <6,1,1> | - sub-block 1 Stage 2 | 7 <0,0,7> | 7 <0,0,7> | - Stage 3 | 7 <0,0,7> | 7 <0,0,7> | - ------------------+---------------+---------------+ - - - -Andersen, et al. Experimental [Page 30] - -RFC 3951 Internet Low Bit Rate Codec December 2004 - - - Stage 1 | 8 <0,0,8> | 8 <0,7,1> | - sub-block 2 Stage 2 | 8 <0,0,8> | 8 <0,0,8> | - Indices Stage 3 | 8 <0,0,8> | 8 <0,0,8> | - for CB ------------------+---------------+---------------+ - sub-blocks Stage 1 | NA | 8 <0,7,1> | - sub-block 3 Stage 2 | NA | 8 <0,0,8> | - Stage 3 | NA | 8 <0,0,8> | - ------------------+---------------+---------------+ - Stage 1 | NA | 8 <0,7,1> | - sub-block 4 Stage 2 | NA | 8 <0,0,8> | - Stage 3 | NA | 8 <0,0,8> | - ------------------+---------------+---------------+ - Sum | 46 <7,0,39> | 94 <6,22,66> | - ----------------------------------+---------------+---------------+ - Stage 1 | 5 <1,2,2> | 5 <1,2,2> | - sub-block 1 Stage 2 | 4 <1,1,2> | 4 <1,2,1> | - Stage 3 | 3 <0,0,3> | 3 <0,0,3> | - ------------------+---------------+---------------+ - Stage 1 | 5 <1,1,3> | 5 <0,2,3> | - sub-block 2 Stage 2 | 4 <0,2,2> | 4 <0,2,2> | - Stage 3 | 3 <0,0,3> | 3 <0,0,3> | - Gains for ------------------+---------------+---------------+ - sub-blocks Stage 1 | NA | 5 <0,1,4> | - sub-block 3 Stage 2 | NA | 4 <0,1,3> | - Stage 3 | NA | 3 <0,0,3> | - ------------------+---------------+---------------+ - Stage 1 | NA | 5 <0,1,4> | - sub-block 4 Stage 2 | NA | 4 <0,1,3> | - Stage 3 | NA | 3 <0,0,3> | - ------------------+---------------+---------------+ - Sum | 24 <3,6,15> | 48 <2,12,34> | - ----------------------------------+---------------+---------------+ - Empty frame indicator | 1 <0,0,1> | 1 <0,0,1> | - ------------------------------------------------------------------- - SUM 304 <48,64,192> 400 <64,96,240> - - Table 3.2. The bitstream definition for iLBC for both the 20 ms - frame size mode and the 30 ms frame size mode. - - When packetized into the payload, the bits MUST be sorted as follows: - All the class 1 bits in the order (from top to bottom) as specified - in the table, all the class 2 bits (from top to bottom), and all the - class 3 bits in the same sequential order. The last bit, the empty - frame indicator, SHOULD be set to zero by the encoder. If this bit - is set to 1 the decoder SHOULD treat the data as a lost frame. For - example, this bit can be set to 1 to indicate lost frame for file - storage format, as in [1]. - - - - -Andersen, et al. Experimental [Page 31] - -RFC 3951 Internet Low Bit Rate Codec December 2004 - - -4. Decoder Principles - - This section describes the principles of each component of the - decoder algorithm. - - +-------------+ +--------+ +---------------+ - payload -> | 1. Get para | -> | 2. LPC | -> | 3. Sc Dequant | -> - +-------------+ +--------+ +---------------+ - - +-------------+ +------------------+ - -> | 4. Mem setup| -> | 5. Construct res |-------> - | +-------------+ +------------------- | - ---------<-----------<-----------<------------ - Sub-frame 0...2/4 (20 ms/30 ms) - - +----------------+ +----------+ - -> | 6. Enhance res | -> | 7. Synth | ------------> - +----------------+ +----------+ - - +-----------------+ - -> | 8. Post Process | ----------------> decoded speech - +-----------------+ - - Figure 4.1. Flow chart of the iLBC decoder. If a frame was lost, - steps 1 to 5 SHOULD be replaced by a PLC algorithm. - - 1. Extract the parameters from the bitstream. - - 2. Decode the LPC and interpolate (section 4.1). - - 3. Construct the 57/58-sample start state (section 4.2). - - 4. Set up the memory by using data from the decoded residual. This - memory is used for codebook construction. For blocks preceding - the start state, both the decoded residual and the target are time - reversed. Sub-frames are decoded in the same order as they were - encoded. - - 5. Construct the residuals of this sub-frame (gain[0]*cbvec[0] + - gain[1]*cbvec[1] + gain[2]*cbvec[2]). Repeat 4 and 5 until the - residual of all sub-blocks has been constructed. - - 6. Enhance the residual with the post filter (section 4.6). - - 7. Synthesis of the residual (section 4.7). - - 8. Post process with HP filter, if desired (section 4.8). - - - - -Andersen, et al. Experimental [Page 32] - -RFC 3951 Internet Low Bit Rate Codec December 2004 - - -4.1. LPC Filter Reconstruction - - The decoding of the LP filter parameters is very straightforward. - For a set of three/six indices, the corresponding LSF vector(s) are - found by simple table lookup. For each of the LSF vectors, the three - split vectors are concatenated to obtain qlsf1 and qlsf2, - respectively (in the 20 ms mode only one LSF vector, qlsf, is - constructed). The next step is the stability check described in - section 3.2.5 followed by the interpolation scheme described in - section 3.2.6 (3.2.7 for 20 ms frames). The only difference is that - only the quantized LSFs are known at the decoder, and hence the - unquantized LSFs are not processed. - - A reference implementation of the LPC filter reconstruction is given - in Appendix A.36. - -4.2. Start State Reconstruction - - The scalar encoded STATE_SHORT_LEN=58 (STATE_SHORT_LEN=57 in the 20 - ms mode) state samples are reconstructed by 1) forming a set of - samples (by table lookup) from the index stream idxVec[n], 2) - multiplying the set with 1/scal=(10^qmax)/4.5, 3) time reversing the - 57/58 samples, 4) filtering the time reversed block with the - dispersion (all-pass) filter used in the encoder (as described in - section 3.5.2); this compensates for the phase distortion of the - earlier filter operation, and 5 reversing the 57/58 samples from the - previous step. - - in(0..(STATE_SHORT_LEN-1)) = time reversed samples from table - look-up, - idxVecDec((STATE_SHORT_LEN-1)..0) - - in(STATE_SHORT_LEN..(2*STATE_SHORT_LEN-1)) = 0 - - Pk(z) = A~rk(z)/A~k(z), where - ___ - \ - A~rk(z)= z^(-LPC_FILTERORDER) + > a~ki*z^(i-(LPC_FILTERORDER-1)) - /__ - i=0...(LPC_FILTERORDER-1) - - and A~k(z) is taken from the block where the start state begins - - in -> Pk(z) -> filtered - - out(k) = filtered(STATE_SHORT_LEN-1-k) + - filtered(2*STATE_SHORT_LEN-1-k), - k=0..(STATE_SHORT_LEN-1) - - - -Andersen, et al. Experimental [Page 33] - -RFC 3951 Internet Low Bit Rate Codec December 2004 - - - The remaining 23/22 samples in the state are reconstructed by the - same adaptive codebook technique described in section 4.3. The - location bit determines whether these are the first or the last 23/22 - samples of the 80-sample state vector. If the remaining 23/22 - samples are the first samples, then the scalar encoded - STATE_SHORT_LEN state samples are time-reversed before initialization - of the adaptive codebook memory vector. - - A reference implementation of the start state reconstruction is given - in Appendix A.44. - -4.3. Excitation Decoding Loop - - The decoding of the LPC excitation vector proceeds in the same order - in which the residual was encoded at the encoder. That is, after the - decoding of the entire 80-sample state vector, the forward sub-blocks - (corresponding to samples occurring after the state vector samples) - are decoded, and then the backward sub-blocks (corresponding to - samples occurring before the state vector) are decoded, resulting in - a fully decoded block of excitation signal samples. - - In particular, each sub-block is decoded by using the multistage - adaptive codebook decoding module described in section 4.4. This - module relies upon an adaptive codebook memory constructed before - each run of the adaptive codebook decoding. The construction of the - adaptive codebook memory in the decoder is identical to the method - outlined in section 3.6.3, except that it is done on the codebook - memory without perceptual weighting. - - For the initial forward sub-block, the last STATE_LEN=80 samples of - the length CB_LMEM=147 adaptive codebook memory are filled with the - samples of the state vector. For subsequent forward sub-blocks, the - first SUBL=40 samples of the adaptive codebook memory are discarded, - the remaining samples are shifted by SUBL samples toward the - beginning of the vector, and the newly decoded SUBL=40 samples are - placed at the end of the adaptive codebook memory. For backward - sub-blocks, the construction is similar, except that every vector of - samples involved is first time reversed. - - A reference implementation of the excitation decoding loop is found - in Appendix A.5. - - - - - - - - - - -Andersen, et al. Experimental [Page 34] - -RFC 3951 Internet Low Bit Rate Codec December 2004 - - -4.4. Multistage Adaptive Codebook Decoding - - The Multistage Adaptive Codebook Decoding module is used at both the - sender (encoder) and the receiver (decoder) ends to produce a - synthetic signal in the residual domain that is eventually used to - produce synthetic speech. The module takes the index values used to - construct vectors that are scaled and summed together to produce a - synthetic signal that is the output of the module. - -4.4.1. Construction of the Decoded Excitation Signal - - The unpacked index values provided at the input to the module are - references to extended codebooks, which are constructed as described - in section 3.6.3, except that they are based on the codebook memory - without the perceptual weighting. The unpacked three indices are - used to look up three codebook vectors. The unpacked three gain - indices are used to decode the corresponding 3 gains. In this - decoding, the successive rescaling, as described in section 3.6.4.2, - is applied. - - A reference implementation of the adaptive codebook decoding is - listed in Appendix A.32. - -4.5. Packet Loss Concealment - - If packet loss occurs, the decoder receives a signal saying that - information regarding a block is lost. For such blocks it is - RECOMMENDED to use a Packet Loss Concealment (PLC) unit to create a - decoded signal that masks the effect of that packet loss. In the - following we will describe an example of a PLC unit that can be used - with the iLBC codec. As the PLC unit is used only at the decoder, - the PLC unit does not affect interoperability between - implementations. Other PLC implementations MAY therefore be used. - - The PLC described operates on the LP filters and the excitation - signals and is based on the following principles: - -4.5.1. Block Received Correctly and Previous Block Also Received - - If the block is received correctly, the PLC only records state - information of the current block that can be used in case the next - block is lost. The LP filter coefficients for each sub-block and the - entire decoded excitation signal are all saved in the decoder state - structure. All of this information will be needed if the following - block is lost. - - - - - - -Andersen, et al. Experimental [Page 35] - -RFC 3951 Internet Low Bit Rate Codec December 2004 - - -4.5.2. Block Not Received - - If the block is not received, the block substitution is based on a - pitch-synchronous repetition of the excitation signal, which is - filtered by the last LP filter of the previous block. The previous - block's information is stored in the decoder state structure. - - A correlation analysis is performed on the previous block's - excitation signal in order to detect the amount of pitch periodicity - and a pitch value. The correlation measure is also used to decide on - the voicing level (the degree to which the previous block's - excitation was a voiced or roughly periodic signal). The excitation - in the previous block is used to create an excitation for the block - to be substituted, such that the pitch of the previous block is - maintained. Therefore, the new excitation is constructed in a - pitch-synchronous manner. In order to avoid a buzzy-sounding - substituted block, a random excitation is mixed with the new pitch - periodic excitation, and the relative use of the two components is - computed from the correlation measure (voicing level). - - For the block to be substituted, the newly constructed excitation - signal is then passed through the LP filter to produce the speech - that will be substituted for the lost block. - - For several consecutive lost blocks, the packet loss concealment - continues in a similar manner. The correlation measure of the last - block received is still used along with the same pitch value. The LP - filters of the last block received are also used again. The energy - of the substituted excitation for consecutive lost blocks is - decreased, leading to a dampened excitation, and therefore to - dampened speech. - -4.5.3. Block Received Correctly When Previous Block Not Received - - For the case in which a block is received correctly when the previous - block was not, the correctly received block's directly decoded speech - (based solely on the received block) is not used as the actual - output. The reason for this is that the directly decoded speech does - not necessarily smoothly merge into the synthetic speech generated - for the previous lost block. If the two signals are not smoothly - merged, an audible discontinuity is accidentally produced. - Therefore, a correlation analysis between the two blocks of - excitation signal (the excitation of the previous concealed block and - that of the current received block) is performed to find the best - phase match. Then a simple overlap-add procedure is performed to - merge the previous excitation smoothly into the current block's - excitation. - - - - -Andersen, et al. Experimental [Page 36] - -RFC 3951 Internet Low Bit Rate Codec December 2004 - - - The exact implementation of the packet loss concealment does not - influence interoperability of the codec. - - A reference implementation of the packet loss concealment is - suggested in Appendix A.14. Exact compliance with this suggested - algorithm is not needed for a reference implementation to be fully - compatible with the overall codec specification. - -4.6. Enhancement - - The decoder contains an enhancement unit that operates on the - reconstructed excitation signal. The enhancement unit increases the - perceptual quality of the reconstructed signal by reducing the - speech-correlated noise in the voiced speech segments. Compared to - traditional postfilters, the enhancer has an advantage in that it can - only modify the excitation signal slightly. This means that there is - no risk of over enhancement. The enhancer works very similarly for - both the 20 ms frame size mode and the 30 ms frame size mode. - - For the mode with 20 ms frame size, the enhancer uses a memory of six - 80-sample excitation blocks prior in time plus the two new 80-sample - excitation blocks. For each block of 160 new unenhanced excitation - samples, 160 enhanced excitation samples are produced. The enhanced - excitation is 40-sample delayed compared to the unenhanced - excitation, as the enhancer algorithm uses lookahead. - - For the mode with 30 ms frame size, the enhancer uses a memory of - five 80-sample excitation blocks prior in time plus the three new - 80-sample excitation blocks. For each block of 240 new unenhanced - excitation samples, 240 enhanced excitation samples are produced. - The enhanced excitation is 80-sample delayed compared to the - unenhanced excitation, as the enhancer algorithm uses lookahead. - - Outline of Enhancer - - The speech enhancement unit operates on sub-blocks of 80 samples, - which means that there are two/three 80 sample sub-blocks per frame. - Each of these two/three sub-blocks is enhanced separately, but in an - analogous manner. - - - - - - - - - - - - -Andersen, et al. Experimental [Page 37] - -RFC 3951 Internet Low Bit Rate Codec December 2004 - - - unenhanced residual - | - | +---------------+ +--------------+ - +-> | 1. Pitch Est | -> | 2. Find PSSQ | --------> - +---------------+ | +--------------+ - +-----<-------<------<--+ - +------------+ enh block 0..1/2 | - -> | 3. Smooth | | - +------------+ | - \ | - /\ | - / \ Already | - / 4. \----------->----------->-----------+ | - \Crit/ Fulfilled | | - \? / v | - \/ | | - \ +-----------------+ +---------+ | | - Not +->| 5. Use Constr. | -> | 6. Mix | -----> - Fulfilled +-----------------+ +---------+ - - ---------------> enhanced residual - - Figure 4.2. Flow chart of the enhancer. - - 1. Pitch estimation of each of the two/three new 80-sample blocks. - - 2. Find the pitch-period-synchronous sequence n (for block k) by a - search around the estimated pitch value. Do this for n=1,2,3, - -1,-2,-3. - - 3. Calculate the smoothed residual generated by the six pitch- - period-synchronous sequences from prior step. - - 4. Check if the smoothed residual satisfies the criterion (section - 4.6.4). - - 5. Use constraint to calculate mixing factor (section 4.6.5). - - 6. Mix smoothed signal with unenhanced residual (pssq(n) n=0). - - The main idea of the enhancer is to find three 80 sample blocks - before and three 80-sample blocks after the analyzed unenhanced sub- - block and to use these to improve the quality of the excitation in - that sub-block. The six blocks are chosen so that they have the - highest possible correlation with the unenhanced sub-block that is - being enhanced. In other words, the six blocks are pitch-period- - synchronous sequences to the unenhanced sub-block. - - - - -Andersen, et al. Experimental [Page 38] - -RFC 3951 Internet Low Bit Rate Codec December 2004 - - - A linear combination of the six pitch-period-synchronous sequences is - calculated that approximates the sub-block. If the squared error - between the approximation and the unenhanced sub-block is small - enough, the enhanced residual is set equal to this approximation. - For the cases when the squared error criterion is not fulfilled, a - linear combination of the approximation and the unenhanced residual - forms the enhanced residual. - -4.6.1. Estimating the Pitch - - Pitch estimates are needed to determine the locations of the pitch- - period-synchronous sequences in a complexity-efficient way. For each - of the new two/three sub-blocks, a pitch estimate is calculated by - finding the maximum correlation in the range from lag 20 to lag 120. - These pitch estimates are used to narrow down the search for the best - possible pitch-period-synchronous sequences. - -4.6.2. Determination of the Pitch-Synchronous Sequences - - Upon receiving the pitch estimates from the prior step, the enhancer - analyzes and enhances one 80-sample sub-block at a time. The pitch- - period-synchronous-sequences pssq(n) can be viewed as vectors of - length 80 samples each shifted n*lag samples from the current sub- - block. The six pitch-period-synchronous-sequences, pssq(-3) to - pssq(-1) and pssq(1) to pssq(3), are found one at a time by the steps - below: - - 1) Calculate the estimate of the position of the pssq(n). For - pssq(n) in front of pssq(0) (n > 0), the location of the pssq(n) - is estimated by moving one pitch estimate forward in time from the - exact location of pssq(n-1). Similarly, pssq(n) behind pssq(0) (n - < 0) is estimated by moving one pitch estimate backward in time - from the exact location of pssq(n+1). If the estimated pssq(n) - vector location is totally within the enhancer memory (Figure - 4.3), steps 2, 3, and 4 are performed, otherwise the pssq(n) is - set to zeros. - - 2) Compute the correlation between the unenhanced excitation and - vectors around the estimated location interval of pssq(n). The - correlation is calculated in the interval estimated location +/- 2 - samples. This results in five correlation values. - - 3) The five correlation values are upsampled by a factor of 4, by - using four simple upsampling filters (MA filters with coefficients - upsFilter1.. upsFilter4). Within these the maximum value is - found, which specifies the best pitch-period with a resolution of - a quarter of a sample. - - - - -Andersen, et al. Experimental [Page 39] - -RFC 3951 Internet Low Bit Rate Codec December 2004 - - - upsFilter1[7]={0.000000 0.000000 0.000000 1.000000 - 0.000000 0.000000 0.000000} - upsFilter2[7]={0.015625 -0.076904 0.288330 0.862061 - -0.106445 0.018799 -0.015625} - upsFilter3[7]={0.023682 -0.124268 0.601563 0.601563 - -0.124268 0.023682 -0.023682} - upsFilter4[7]={0.018799 -0.106445 0.862061 0.288330 - -0.076904 0.015625 -0.018799} - - 4) Generate the pssq(n) vector by upsampling of the excitation memory - and extracting the sequence that corresponds to the lag delay that - was calculated in prior step. - - With the steps above, all the pssq(n) can be found in an iterative - manner, first moving backward in time from pssq(0) and then forward - in time from pssq(0). - - - 0 159 319 479 639 - +---------------------------------------------------------------+ - | -5 | -4 | -3 | -2 | -1 | 0 | 1 | 2 | - +---------------------------------------------------------------+ - |pssq 0 | - |pssq -1| |pssq 1 | - |pssq -2| |pssq 2 | - |pssq -3| |pssq 3 | - - Figure 4.3. Enhancement for 20 ms frame size. - - Figure 4.3 depicts pitch-period-synchronous sequences in the - enhancement of the first 80 sample block in the 20 ms frame size - mode. The unenhanced signal input is stored in the last two sub- - blocks (1 - 2), and the six other sub-blocks contain unenhanced - residual prior-in-time. We perform the enhancement algorithm on two - blocks of 80 samples, where the first of the two blocks consists of - the last 40 samples of sub-block 0 and the first 40 samples of sub- - block 1. The second 80-sample block consists of the last 40 samples - of sub-block 1 and the first 40 samples of sub-block 2. - - - - - - - - - - - - - -Andersen, et al. Experimental [Page 40] - -RFC 3951 Internet Low Bit Rate Codec December 2004 - - - 0 159 319 479 639 - +---------------------------------------------------------------+ - | -4 | -3 | -2 | -1 | 0 | 1 | 2 | 3 | - +---------------------------------------------------------------+ - |pssq 0 | - |pssq -1| |pssq 1 | - |pssq -2| |pssq 2 | - |pssq -3| |pssq 3 | - - Figure 4.4. Enhancement for 30 ms frame size. - - Figure 4.4 depicts pitch-period-synchronous sequences in the - enhancement of the first 80-sample block in the 30 ms frame size - mode. The unenhanced signal input is stored in the last three sub- - blocks (1 - 3). The five other sub-blocks contain unenhanced - residual prior-in-time. The enhancement algorithm is performed on - the three 80 sample sub-blocks 0, 1, and 2. - -4.6.3. Calculation of the Smoothed Excitation - - A linear combination of the six pssq(n) (n!=0) form a smoothed - approximation, z, of pssq(0). Most of the weight is put on the - sequences that are close to pssq(0), as these are likely to be most - similar to pssq(0). The smoothed vector is also rescaled so that the - energy of z is the same as the energy of pssq(0). - - ___ - \ - y = > pssq(i) * pssq_weight(i) - /__ - i=-3,-2,-1,1,2,3 - - pssq_weight(i) = 0.5*(1-cos(2*pi*(i+4)/(2*3+2))) - - z = C * y, where C = ||pssq(0)||/||y|| - -4.6.4. Enhancer Criterion - - The criterion of the enhancer is that the enhanced excitation is not - allowed to differ much from the unenhanced excitation. This - criterion is checked for each 80-sample sub-block. - - e < (b * ||pssq(0)||^2), where b=0.05 and (Constraint 1) - - e = (pssq(0)-z)*(pssq(0)-z), and "*" means the dot product - - - - - - -Andersen, et al. Experimental [Page 41] - -RFC 3951 Internet Low Bit Rate Codec December 2004 - - -4.6.5. Enhancing the excitation - - From the criterion in the previous section, it is clear that the - excitation is not allowed to change much. The purpose of this - constraint is to prevent the creation of an enhanced signal - significantly different from the original signal. This also means - that the constraint limits the numerical size of the errors that the - enhancement procedure can make. That is especially important in - unvoiced segments and background noise segments for which increased - periodicity could lead to lower perceived quality. - - When the constraint in the prior section is not met, the enhanced - residual is instead calculated through a constrained optimization by - using the Lagrange multiplier technique. The new constraint is that - - e = (b * ||pssq(0)||^2) (Constraint 2) - - We distinguish two solution regions for the optimization: 1) the - region where the first constraint is fulfilled and 2) the region - where the first constraint is not fulfilled and the second constraint - must be used. - - In the first case, where the second constraint is not needed, the - optimized re-estimated vector is simply z, the energy-scaled version - of y. - - In the second case, where the second constraint is activated and - becomes an equality constraint, we have - - z= A*y + B*pssq(0) - - where - - A = sqrt((b-b^2/4)*(w00*w00)/ (w11*w00 + w10*w10)) and - - w11 = pssq(0)*pssq(0) - w00 = y*y - w10 = y*pssq(0) (* symbolizes the dot product) - - and - - B = 1 - b/2 - A * w10/w00 - - Appendix A.16 contains a listing of a reference implementation for - the enhancement method. - - - - - - -Andersen, et al. Experimental [Page 42] - -RFC 3951 Internet Low Bit Rate Codec December 2004 - - -4.7. Synthesis Filtering - - Upon decoding or PLC of the LP excitation block, the decoded speech - block is obtained by running the decoded LP synthesis filter, - 1/A~k(z), over the block. The synthesis filters have to be shifted - to compensate for the delay in the enhancer. For 20 ms frame size - mode, they SHOULD be shifted one 40-sample sub-block, and for 30 ms - frame size mode, they SHOULD be shifted two 40-sample sub-blocks. - The LP coefficients SHOULD be changed at the first sample of every - sub-block while keeping the filter state. For PLC blocks, one - solution is to apply the last LP coefficients of the last decoded - speech block for all sub-blocks. - - The reference implementation for the synthesis filtering can be found - in Appendix A.48. - -4.8. Post Filtering - - If desired, the decoded block can be filtered by a high-pass filter. - This removes the low frequencies of the decoded signal. A reference - implementation of this, with cutoff at 65 Hz, is shown in Appendix - A.30. - -5. Security Considerations - - This algorithm for the coding of speech signals is not subject to any - known security consideration; however, its RTP payload format [1] is - subject to several considerations, which are addressed there. - Confidentiality of the media streams is achieved by encryption; - therefore external mechanisms, such as SRTP [5], MAY be used for that - purpose. - -6. Evaluation of the iLBC Implementations - - It is possible and suggested to evaluate certain iLBC implementation - by utilizing methodology and tools available at - http://www.ilbcfreeware.org/evaluation.html - -7. References - -7.1. Normative References - - [1] Duric, A. and S. Andersen, "Real-time Transport Protocol (RTP) - Payload Format for internet Low Bit Rate Codec (iLBC) Speech", - RFC 3952, December 2004. - - [2] Bradner, S., "Key words for use in RFCs to Indicate Requirement - Levels", BCP 14, RFC 2119, March 1997. - - - -Andersen, et al. Experimental [Page 43] - -RFC 3951 Internet Low Bit Rate Codec December 2004 - - - [3] PacketCable(TM) Audio/Video Codecs Specification, Cable - Television Laboratories, Inc. - -7.2. Informative References - - [4] ITU-T Recommendation G.711, available online from the ITU - bookstore at http://www.itu.int. - - [5] Baugher, M., McGrew, D., Naslund, M., Carrara, E., and K. Norman, - "The Secure Real Time Transport Protocol (SRTP)", RFC 3711, March - 2004. - -8. Acknowledgements - - This extensive work, besides listed authors, has the following - authors, who could not have been listed among "official" authors (due - to IESG restrictions in the number of authors who can be listed): - - Manohar N. Murthi (Department of Electrical and Computer - Engineering, University of Miami), Fredrik Galschiodt, Julian - Spittka, and Jan Skoglund (Global IP Sound). - - The authors are deeply indebted to the following people and thank - them sincerely: - - Henry Sinnreich, Patrik Faltstrom, Alan Johnston, and Jean- - Francois Mule for great support of the iLBC initiative and for - valuable feedback and comments. - - Peter Vary, Frank Mertz, and Christoph Erdmann (RWTH Aachen); - Vladimir Cuperman (Niftybox LLC); Thomas Eriksson (Chalmers Univ - of Tech), and Gernot Kubin (TU Graz), for thorough review of the - iLBC document and their valuable feedback and remarks. - - - - - - - - - - - - - - - - - - -Andersen, et al. Experimental [Page 44] - -RFC 3951 Internet Low Bit Rate Codec December 2004 - - -APPENDIX A. Reference Implementation - - This appendix contains the complete c-code for a reference - implementation of encoder and decoder for the specified codec. - - The c-code consists of the following files with highest-level - functions: - - iLBC_test.c: main function for evaluation purpose - iLBC_encode.h: encoder header - iLBC_encode.c: encoder function - iLBC_decode.h: decoder header - iLBC_decode.c: decoder function - - The following files contain global defines and constants: - - iLBC_define.h: global defines - constants.h: global constants header - constants.c: global constants memory allocations - - The following files contain subroutines: - - anaFilter.h: lpc analysis filter header - anaFilter.c: lpc analysis filter function - createCB.h: codebook construction header - createCB.c: codebook construction function - doCPLC.h: packet loss concealment header - doCPLC.c: packet loss concealment function - enhancer.h: signal enhancement header - enhancer.c: signal enhancement function - filter.h: general filter header - filter.c: general filter functions - FrameClassify.h: start state classification header - FrameClassify.c: start state classification function - gainquant.h: gain quantization header - gainquant.c: gain quantization function - getCBvec.h: codebook vector construction header - getCBvec.c: codebook vector construction function - helpfun.h: general purpose header - helpfun.c: general purpose functions - hpInput.h: input high pass filter header - hpInput.c: input high pass filter function - hpOutput.h: output high pass filter header - hpOutput.c: output high pass filter function - iCBConstruct.h: excitation decoding header - iCBConstruct.c: excitation decoding function - iCBSearch.h: excitation encoding header - iCBSearch.c: excitation encoding function - - - -Andersen, et al. Experimental [Page 45] - -RFC 3951 Internet Low Bit Rate Codec December 2004 - - - LPCdecode.h: lpc decoding header - LPCdecode.c: lpc decoding function - LPCencode.h: lpc encoding header - LPCencode.c: lpc encoding function - lsf.h: line spectral frequencies header - lsf.c: line spectral frequencies functions - packing.h: bitstream packetization header - packing.c: bitstream packetization functions - StateConstructW.h: state decoding header - StateConstructW.c: state decoding functions - StateSearchW.h: state encoding header - StateSearchW.c: state encoding function - syntFilter.h: lpc synthesis filter header - syntFilter.c: lpc synthesis filter function - - The implementation is portable and should work on many different - platforms. However, it is not difficult to optimize the - implementation on particular platforms, an exercise left to the - reader. - -A.1. iLBC_test.c - - /****************************************************************** - - iLBC Speech Coder ANSI-C Source Code - - iLBC_test.c - - Copyright (C) The Internet Society (2004). - All Rights Reserved. - - ******************************************************************/ - - #include - #include - #include - #include - #include "iLBC_define.h" - #include "iLBC_encode.h" - #include "iLBC_decode.h" - - /* Runtime statistics */ - #include - - #define ILBCNOOFWORDS_MAX (NO_OF_BYTES_30MS/2) - - /*----------------------------------------------------------------* - * Encoder interface function - - - -Andersen, et al. Experimental [Page 46] - -RFC 3951 Internet Low Bit Rate Codec December 2004 - - - *---------------------------------------------------------------*/ - - short encode( /* (o) Number of bytes encoded */ - iLBC_Enc_Inst_t *iLBCenc_inst, - /* (i/o) Encoder instance */ - short *encoded_data, /* (o) The encoded bytes */ - short *data /* (i) The signal block to encode*/ - ){ - float block[BLOCKL_MAX]; - int k; - - /* convert signal to float */ - - for (k=0; kblockl; k++) - block[k] = (float)data[k]; - - /* do the actual encoding */ - - iLBC_encode((unsigned char *)encoded_data, block, iLBCenc_inst); - - - return (iLBCenc_inst->no_of_bytes); - } - - /*----------------------------------------------------------------* - * Decoder interface function - *---------------------------------------------------------------*/ - - short decode( /* (o) Number of decoded samples */ - iLBC_Dec_Inst_t *iLBCdec_inst, /* (i/o) Decoder instance */ - short *decoded_data, /* (o) Decoded signal block*/ - short *encoded_data, /* (i) Encoded bytes */ - short mode /* (i) 0=PL, 1=Normal */ - ){ - int k; - float decblock[BLOCKL_MAX], dtmp; - - /* check if mode is valid */ - - if (mode<0 || mode>1) { - printf("\nERROR - Wrong mode - 0, 1 allowed\n"); exit(3);} - - /* do actual decoding of block */ - - iLBC_decode(decblock, (unsigned char *)encoded_data, - iLBCdec_inst, mode); - - /* convert to short */ - - - -Andersen, et al. Experimental [Page 47] - -RFC 3951 Internet Low Bit Rate Codec December 2004 - - - for (k=0; kblockl; k++){ - dtmp=decblock[k]; - - if (dtmpMAX_SAMPLE) - dtmp=MAX_SAMPLE; - decoded_data[k] = (short) dtmp; - } - - return (iLBCdec_inst->blockl); - } - - /*---------------------------------------------------------------* - * Main program to test iLBC encoding and decoding - * - * Usage: - * exefile_name.exe - * - * : Input file, speech for encoder (16-bit pcm file) - * : Bit stream output from the encoder - * : Output file, decoded speech (16-bit pcm file) - * : Bit error file, optional (16-bit) - * 1 - Packet received correctly - * 0 - Packet Lost - * - *--------------------------------------------------------------*/ - - int main(int argc, char* argv[]) - { - - /* Runtime statistics */ - - float starttime; - float runtime; - float outtime; - - FILE *ifileid,*efileid,*ofileid, *cfileid; - short data[BLOCKL_MAX]; - short encoded_data[ILBCNOOFWORDS_MAX], decoded_data[BLOCKL_MAX]; - int len; - short pli, mode; - int blockcount = 0; - int packetlosscount = 0; - - /* Create structs */ - iLBC_Enc_Inst_t Enc_Inst; - iLBC_Dec_Inst_t Dec_Inst; - - - -Andersen, et al. Experimental [Page 48] - -RFC 3951 Internet Low Bit Rate Codec December 2004 - - - /* get arguments and open files */ - - if ((argc!=5) && (argc!=6)) { - fprintf(stderr, - "\n*-----------------------------------------------*\n"); - fprintf(stderr, - " %s <20,30> input encoded decoded (channel)\n\n", - argv[0]); - fprintf(stderr, - " mode : Frame size for the encoding/decoding\n"); - fprintf(stderr, - " 20 - 20 ms\n"); - fprintf(stderr, - " 30 - 30 ms\n"); - fprintf(stderr, - " input : Speech for encoder (16-bit pcm file)\n"); - fprintf(stderr, - " encoded : Encoded bit stream\n"); - fprintf(stderr, - " decoded : Decoded speech (16-bit pcm file)\n"); - fprintf(stderr, - " channel : Packet loss pattern, optional (16-bit)\n"); - fprintf(stderr, - " 1 - Packet received correctly\n"); - fprintf(stderr, - " 0 - Packet Lost\n"); - fprintf(stderr, - "*-----------------------------------------------*\n\n"); - exit(1); - } - mode=atoi(argv[1]); - if (mode != 20 && mode != 30) { - fprintf(stderr,"Wrong mode %s, must be 20, or 30\n", - argv[1]); - exit(2); - } - if ( (ifileid=fopen(argv[2],"rb")) == NULL) { - fprintf(stderr,"Cannot open input file %s\n", argv[2]); - exit(2);} - if ( (efileid=fopen(argv[3],"wb")) == NULL) { - fprintf(stderr, "Cannot open encoded file %s\n", - argv[3]); exit(1);} - if ( (ofileid=fopen(argv[4],"wb")) == NULL) { - fprintf(stderr, "Cannot open decoded file %s\n", - argv[4]); exit(1);} - if (argc==6) { - if( (cfileid=fopen(argv[5],"rb")) == NULL) { - fprintf(stderr, "Cannot open channel file %s\n", - - - -Andersen, et al. Experimental [Page 49] - -RFC 3951 Internet Low Bit Rate Codec December 2004 - - - argv[5]); - exit(1); - } - } else { - cfileid=NULL; - } - - /* print info */ - - fprintf(stderr, "\n"); - fprintf(stderr, - "*---------------------------------------------------*\n"); - fprintf(stderr, - "* *\n"); - fprintf(stderr, - "* iLBC test program *\n"); - fprintf(stderr, - "* *\n"); - fprintf(stderr, - "* *\n"); - fprintf(stderr, - "*---------------------------------------------------*\n"); - fprintf(stderr,"\nMode : %2d ms\n", mode); - fprintf(stderr,"Input file : %s\n", argv[2]); - fprintf(stderr,"Encoded file : %s\n", argv[3]); - fprintf(stderr,"Output file : %s\n", argv[4]); - if (argc==6) { - fprintf(stderr,"Channel file : %s\n", argv[5]); - } - fprintf(stderr,"\n"); - - /* Initialization */ - - initEncode(&Enc_Inst, mode); - initDecode(&Dec_Inst, mode, 1); - - /* Runtime statistics */ - - starttime=clock()/(float)CLOCKS_PER_SEC; - - /* loop over input blocks */ - - while (fread(data,sizeof(short),Enc_Inst.blockl,ifileid)== - Enc_Inst.blockl) { - - blockcount++; - - /* encoding */ - - - -Andersen, et al. Experimental [Page 50] - -RFC 3951 Internet Low Bit Rate Codec December 2004 - - - fprintf(stderr, "--- Encoding block %i --- ",blockcount); - len=encode(&Enc_Inst, encoded_data, data); - fprintf(stderr, "\r"); - - /* write byte file */ - - fwrite(encoded_data, sizeof(unsigned char), len, efileid); - - /* get channel data if provided */ - if (argc==6) { - if (fread(&pli, sizeof(short), 1, cfileid)) { - if ((pli!=0)&&(pli!=1)) { - fprintf(stderr, "Error in channel file\n"); - exit(0); - } - if (pli==0) { - /* Packet loss -> remove info from frame */ - memset(encoded_data, 0, - sizeof(short)*ILBCNOOFWORDS_MAX); - packetlosscount++; - } - } else { - fprintf(stderr, "Error. Channel file too short\n"); - exit(0); - } - } else { - pli=1; - } - - /* decoding */ - - fprintf(stderr, "--- Decoding block %i --- ",blockcount); - - len=decode(&Dec_Inst, decoded_data, encoded_data, pli); - fprintf(stderr, "\r"); - - /* write output file */ - - fwrite(decoded_data,sizeof(short),len,ofileid); - } - - /* Runtime statistics */ - - runtime = (float)(clock()/(float)CLOCKS_PER_SEC-starttime); - outtime = (float)((float)blockcount*(float)mode/1000.0); - printf("\n\nLength of speech file: %.1f s\n", outtime); - printf("Packet loss : %.1f%%\n", - 100.0*(float)packetlosscount/(float)blockcount); - - - -Andersen, et al. Experimental [Page 51] - -RFC 3951 Internet Low Bit Rate Codec December 2004 - - - printf("Time to run iLBC :"); - printf(" %.1f s (%.1f %% of realtime)\n\n", runtime, - (100*runtime/outtime)); - - /* close files */ - - fclose(ifileid); fclose(efileid); fclose(ofileid); - if (argc==6) { - fclose(cfileid); - } - return(0); - } - -A.2. iLBC_encode.h - - /****************************************************************** - - iLBC Speech Coder ANSI-C Source Code - - iLBC_encode.h - - Copyright (C) The Internet Society (2004). - All Rights Reserved. - - ******************************************************************/ - - #ifndef __iLBC_ILBCENCODE_H - #define __iLBC_ILBCENCODE_H - - #include "iLBC_define.h" - - short initEncode( /* (o) Number of bytes - encoded */ - iLBC_Enc_Inst_t *iLBCenc_inst, /* (i/o) Encoder instance */ - int mode /* (i) frame size mode */ - ); - - void iLBC_encode( - - unsigned char *bytes, /* (o) encoded data bits iLBC */ - float *block, /* (o) speech vector to - encode */ - iLBC_Enc_Inst_t *iLBCenc_inst /* (i/o) the general encoder - state */ - ); - - #endif - - - - -Andersen, et al. Experimental [Page 52] - -RFC 3951 Internet Low Bit Rate Codec December 2004 - - -A.3. iLBC_encode.c - - /****************************************************************** - - iLBC Speech Coder ANSI-C Source Code - - iLBC_encode.c - - Copyright (C) The Internet Society (2004). - All Rights Reserved. - - ******************************************************************/ - - #include - #include - #include - - #include "iLBC_define.h" - #include "LPCencode.h" - #include "FrameClassify.h" - #include "StateSearchW.h" - #include "StateConstructW.h" - #include "helpfun.h" - #include "constants.h" - #include "packing.h" - #include "iCBSearch.h" - #include "iCBConstruct.h" - #include "hpInput.h" - #include "anaFilter.h" - #include "syntFilter.h" - - /*----------------------------------------------------------------* - * Initiation of encoder instance. - *---------------------------------------------------------------*/ - - short initEncode( /* (o) Number of bytes - encoded */ - iLBC_Enc_Inst_t *iLBCenc_inst, /* (i/o) Encoder instance */ - int mode /* (i) frame size mode */ - ){ - iLBCenc_inst->mode = mode; - if (mode==30) { - iLBCenc_inst->blockl = BLOCKL_30MS; - iLBCenc_inst->nsub = NSUB_30MS; - iLBCenc_inst->nasub = NASUB_30MS; - iLBCenc_inst->lpc_n = LPC_N_30MS; - iLBCenc_inst->no_of_bytes = NO_OF_BYTES_30MS; - iLBCenc_inst->no_of_words = NO_OF_WORDS_30MS; - - - -Andersen, et al. Experimental [Page 53] - -RFC 3951 Internet Low Bit Rate Codec December 2004 - - - iLBCenc_inst->state_short_len=STATE_SHORT_LEN_30MS; - /* ULP init */ - iLBCenc_inst->ULP_inst=&ULP_30msTbl; - } - else if (mode==20) { - iLBCenc_inst->blockl = BLOCKL_20MS; - iLBCenc_inst->nsub = NSUB_20MS; - iLBCenc_inst->nasub = NASUB_20MS; - iLBCenc_inst->lpc_n = LPC_N_20MS; - iLBCenc_inst->no_of_bytes = NO_OF_BYTES_20MS; - iLBCenc_inst->no_of_words = NO_OF_WORDS_20MS; - iLBCenc_inst->state_short_len=STATE_SHORT_LEN_20MS; - /* ULP init */ - iLBCenc_inst->ULP_inst=&ULP_20msTbl; - } - else { - exit(2); - } - - memset((*iLBCenc_inst).anaMem, 0, - LPC_FILTERORDER*sizeof(float)); - memcpy((*iLBCenc_inst).lsfold, lsfmeanTbl, - LPC_FILTERORDER*sizeof(float)); - memcpy((*iLBCenc_inst).lsfdeqold, lsfmeanTbl, - LPC_FILTERORDER*sizeof(float)); - memset((*iLBCenc_inst).lpc_buffer, 0, - (LPC_LOOKBACK+BLOCKL_MAX)*sizeof(float)); - memset((*iLBCenc_inst).hpimem, 0, 4*sizeof(float)); - - return (iLBCenc_inst->no_of_bytes); - } - - /*----------------------------------------------------------------* - * main encoder function - *---------------------------------------------------------------*/ - - void iLBC_encode( - unsigned char *bytes, /* (o) encoded data bits iLBC */ - float *block, /* (o) speech vector to - encode */ - iLBC_Enc_Inst_t *iLBCenc_inst /* (i/o) the general encoder - state */ - ){ - - float data[BLOCKL_MAX]; - float residual[BLOCKL_MAX], reverseResidual[BLOCKL_MAX]; - - int start, idxForMax, idxVec[STATE_LEN]; - - - -Andersen, et al. Experimental [Page 54] - -RFC 3951 Internet Low Bit Rate Codec December 2004 - - - float reverseDecresidual[BLOCKL_MAX], mem[CB_MEML]; - int n, k, meml_gotten, Nfor, Nback, i, pos; - int gain_index[CB_NSTAGES*NASUB_MAX], - extra_gain_index[CB_NSTAGES]; - int cb_index[CB_NSTAGES*NASUB_MAX],extra_cb_index[CB_NSTAGES]; - int lsf_i[LSF_NSPLIT*LPC_N_MAX]; - unsigned char *pbytes; - int diff, start_pos, state_first; - float en1, en2; - int index, ulp, firstpart; - int subcount, subframe; - float weightState[LPC_FILTERORDER]; - float syntdenum[NSUB_MAX*(LPC_FILTERORDER+1)]; - float weightdenum[NSUB_MAX*(LPC_FILTERORDER+1)]; - float decresidual[BLOCKL_MAX]; - - /* high pass filtering of input signal if such is not done - prior to calling this function */ - - hpInput(block, iLBCenc_inst->blockl, - data, (*iLBCenc_inst).hpimem); - - /* otherwise simply copy */ - - /*memcpy(data,block,iLBCenc_inst->blockl*sizeof(float));*/ - - /* LPC of hp filtered input data */ - - LPCencode(syntdenum, weightdenum, lsf_i, data, iLBCenc_inst); - - - /* inverse filter to get residual */ - - for (n=0; nnsub; n++) { - anaFilter(&data[n*SUBL], &syntdenum[n*(LPC_FILTERORDER+1)], - SUBL, &residual[n*SUBL], iLBCenc_inst->anaMem); - } - - /* find state location */ - - start = FrameClassify(iLBCenc_inst, residual); - - /* check if state should be in first or last part of the - two subframes */ - - diff = STATE_LEN - iLBCenc_inst->state_short_len; - en1 = 0; - index = (start-1)*SUBL; - - - -Andersen, et al. Experimental [Page 55] - -RFC 3951 Internet Low Bit Rate Codec December 2004 - - - for (i = 0; i < iLBCenc_inst->state_short_len; i++) { - en1 += residual[index+i]*residual[index+i]; - } - en2 = 0; - index = (start-1)*SUBL+diff; - for (i = 0; i < iLBCenc_inst->state_short_len; i++) { - en2 += residual[index+i]*residual[index+i]; - } - - - if (en1 > en2) { - state_first = 1; - start_pos = (start-1)*SUBL; - } else { - state_first = 0; - start_pos = (start-1)*SUBL + diff; - } - - /* scalar quantization of state */ - - StateSearchW(iLBCenc_inst, &residual[start_pos], - &syntdenum[(start-1)*(LPC_FILTERORDER+1)], - &weightdenum[(start-1)*(LPC_FILTERORDER+1)], &idxForMax, - idxVec, iLBCenc_inst->state_short_len, state_first); - - StateConstructW(idxForMax, idxVec, - &syntdenum[(start-1)*(LPC_FILTERORDER+1)], - &decresidual[start_pos], iLBCenc_inst->state_short_len); - - /* predictive quantization in state */ - - if (state_first) { /* put adaptive part in the end */ - - /* setup memory */ - - memset(mem, 0, - (CB_MEML-iLBCenc_inst->state_short_len)*sizeof(float)); - memcpy(mem+CB_MEML-iLBCenc_inst->state_short_len, - decresidual+start_pos, - iLBCenc_inst->state_short_len*sizeof(float)); - memset(weightState, 0, LPC_FILTERORDER*sizeof(float)); - - /* encode sub-frames */ - - iCBSearch(iLBCenc_inst, extra_cb_index, extra_gain_index, - &residual[start_pos+iLBCenc_inst->state_short_len], - mem+CB_MEML-stMemLTbl, - stMemLTbl, diff, CB_NSTAGES, - - - -Andersen, et al. Experimental [Page 56] - -RFC 3951 Internet Low Bit Rate Codec December 2004 - - - &weightdenum[start*(LPC_FILTERORDER+1)], - weightState, 0); - - /* construct decoded vector */ - - iCBConstruct( - &decresidual[start_pos+iLBCenc_inst->state_short_len], - extra_cb_index, extra_gain_index, - mem+CB_MEML-stMemLTbl, - stMemLTbl, diff, CB_NSTAGES); - - } - else { /* put adaptive part in the beginning */ - - /* create reversed vectors for prediction */ - - for (k=0; kstate_short_len)]; - } - - /* setup memory */ - - meml_gotten = iLBCenc_inst->state_short_len; - for (k=0; knsub-start-1; - - - if ( Nfor > 0 ) { - - /* setup memory */ - - memset(mem, 0, (CB_MEML-STATE_LEN)*sizeof(float)); - memcpy(mem+CB_MEML-STATE_LEN, decresidual+(start-1)*SUBL, - STATE_LEN*sizeof(float)); - memset(weightState, 0, LPC_FILTERORDER*sizeof(float)); - - /* loop over sub-frames to encode */ - - for (subframe=0; subframe 0 ) { - - /* create reverse order vectors */ - - for (n=0; nnsub+1-start); - - - if ( meml_gotten > CB_MEML ) { - meml_gotten=CB_MEML; - } - for (k=0; klpc_n; k++) { - packsplit(&lsf_i[k], &firstpart, &lsf_i[k], - iLBCenc_inst->ULP_inst->lsf_bits[k][ulp], - iLBCenc_inst->ULP_inst->lsf_bits[k][ulp]+ - iLBCenc_inst->ULP_inst->lsf_bits[k][ulp+1]+ - iLBCenc_inst->ULP_inst->lsf_bits[k][ulp+2]); - dopack( &pbytes, firstpart, - iLBCenc_inst->ULP_inst->lsf_bits[k][ulp], &pos); - } - - /* Start block info */ - - packsplit(&start, &firstpart, &start, - iLBCenc_inst->ULP_inst->start_bits[ulp], - iLBCenc_inst->ULP_inst->start_bits[ulp]+ - iLBCenc_inst->ULP_inst->start_bits[ulp+1]+ - iLBCenc_inst->ULP_inst->start_bits[ulp+2]); - dopack( &pbytes, firstpart, - iLBCenc_inst->ULP_inst->start_bits[ulp], &pos); - - packsplit(&state_first, &firstpart, &state_first, - iLBCenc_inst->ULP_inst->startfirst_bits[ulp], - iLBCenc_inst->ULP_inst->startfirst_bits[ulp]+ - iLBCenc_inst->ULP_inst->startfirst_bits[ulp+1]+ - iLBCenc_inst->ULP_inst->startfirst_bits[ulp+2]); - dopack( &pbytes, firstpart, - iLBCenc_inst->ULP_inst->startfirst_bits[ulp], &pos); - - packsplit(&idxForMax, &firstpart, &idxForMax, - iLBCenc_inst->ULP_inst->scale_bits[ulp], - iLBCenc_inst->ULP_inst->scale_bits[ulp]+ - iLBCenc_inst->ULP_inst->scale_bits[ulp+1]+ - iLBCenc_inst->ULP_inst->scale_bits[ulp+2]); - dopack( &pbytes, firstpart, - iLBCenc_inst->ULP_inst->scale_bits[ulp], &pos); - - for (k=0; kstate_short_len; k++) { - packsplit(idxVec+k, &firstpart, idxVec+k, - iLBCenc_inst->ULP_inst->state_bits[ulp], - iLBCenc_inst->ULP_inst->state_bits[ulp]+ - iLBCenc_inst->ULP_inst->state_bits[ulp+1]+ - iLBCenc_inst->ULP_inst->state_bits[ulp+2]); - dopack( &pbytes, firstpart, - iLBCenc_inst->ULP_inst->state_bits[ulp], &pos); - } - - - - -Andersen, et al. Experimental [Page 61] - -RFC 3951 Internet Low Bit Rate Codec December 2004 - - - /* 23/22 (20ms/30ms) sample block */ - - for (k=0;kULP_inst->extra_cb_index[k][ulp], - iLBCenc_inst->ULP_inst->extra_cb_index[k][ulp]+ - iLBCenc_inst->ULP_inst->extra_cb_index[k][ulp+1]+ - iLBCenc_inst->ULP_inst->extra_cb_index[k][ulp+2]); - dopack( &pbytes, firstpart, - iLBCenc_inst->ULP_inst->extra_cb_index[k][ulp], - &pos); - } - - for (k=0;kULP_inst->extra_cb_gain[k][ulp], - iLBCenc_inst->ULP_inst->extra_cb_gain[k][ulp]+ - iLBCenc_inst->ULP_inst->extra_cb_gain[k][ulp+1]+ - iLBCenc_inst->ULP_inst->extra_cb_gain[k][ulp+2]); - dopack( &pbytes, firstpart, - iLBCenc_inst->ULP_inst->extra_cb_gain[k][ulp], - &pos); - } - - /* The two/four (20ms/30ms) 40 sample sub-blocks */ - - for (i=0; inasub; i++) { - for (k=0; kULP_inst->cb_index[i][k][ulp], - iLBCenc_inst->ULP_inst->cb_index[i][k][ulp]+ - iLBCenc_inst->ULP_inst->cb_index[i][k][ulp+1]+ - iLBCenc_inst->ULP_inst->cb_index[i][k][ulp+2]); - dopack( &pbytes, firstpart, - iLBCenc_inst->ULP_inst->cb_index[i][k][ulp], - &pos); - } - } - - for (i=0; inasub; i++) { - for (k=0; kULP_inst->cb_gain[i][k][ulp], - iLBCenc_inst->ULP_inst->cb_gain[i][k][ulp]+ - - - -Andersen, et al. Experimental [Page 62] - -RFC 3951 Internet Low Bit Rate Codec December 2004 - - - iLBCenc_inst->ULP_inst->cb_gain[i][k][ulp+1]+ - iLBCenc_inst->ULP_inst->cb_gain[i][k][ulp+2]); - dopack( &pbytes, firstpart, - iLBCenc_inst->ULP_inst->cb_gain[i][k][ulp], - &pos); - } - } - } - - /* set the last bit to zero (otherwise the decoder - will treat it as a lost frame) */ - dopack( &pbytes, 0, 1, &pos); - } - -A.4. iLBC_decode.h - - /****************************************************************** - - iLBC Speech Coder ANSI-C Source Code - - iLBC_decode.h - - Copyright (C) The Internet Society (2004). - All Rights Reserved. - - ******************************************************************/ - - #ifndef __iLBC_ILBCDECODE_H - #define __iLBC_ILBCDECODE_H - - #include "iLBC_define.h" - - short initDecode( /* (o) Number of decoded - samples */ - iLBC_Dec_Inst_t *iLBCdec_inst, /* (i/o) Decoder instance */ - int mode, /* (i) frame size mode */ - int use_enhancer /* (i) 1 to use enhancer - 0 to run without - enhancer */ - ); - - void iLBC_decode( - float *decblock, /* (o) decoded signal block */ - unsigned char *bytes, /* (i) encoded signal bits */ - iLBC_Dec_Inst_t *iLBCdec_inst, /* (i/o) the decoder state - structure */ - int mode /* (i) 0: bad packet, PLC, - 1: normal */ - - - -Andersen, et al. Experimental [Page 63] - -RFC 3951 Internet Low Bit Rate Codec December 2004 - - - ); - - #endif - -A.5. iLBC_decode.c - - /****************************************************************** - - iLBC Speech Coder ANSI-C Source Code - - iLBC_decode.c - - Copyright (C) The Internet Society (2004). - All Rights Reserved. - - ******************************************************************/ - - #include - #include - - #include "iLBC_define.h" - #include "StateConstructW.h" - #include "LPCdecode.h" - #include "iCBConstruct.h" - #include "doCPLC.h" - #include "helpfun.h" - #include "constants.h" - #include "packing.h" - #include "string.h" - #include "enhancer.h" - #include "hpOutput.h" - #include "syntFilter.h" - - /*----------------------------------------------------------------* - * Initiation of decoder instance. - *---------------------------------------------------------------*/ - - short initDecode( /* (o) Number of decoded - samples */ - iLBC_Dec_Inst_t *iLBCdec_inst, /* (i/o) Decoder instance */ - int mode, /* (i) frame size mode */ - int use_enhancer /* (i) 1 to use enhancer - 0 to run without - enhancer */ - ){ - int i; - - iLBCdec_inst->mode = mode; - - - -Andersen, et al. Experimental [Page 64] - -RFC 3951 Internet Low Bit Rate Codec December 2004 - - - if (mode==30) { - iLBCdec_inst->blockl = BLOCKL_30MS; - iLBCdec_inst->nsub = NSUB_30MS; - iLBCdec_inst->nasub = NASUB_30MS; - iLBCdec_inst->lpc_n = LPC_N_30MS; - iLBCdec_inst->no_of_bytes = NO_OF_BYTES_30MS; - iLBCdec_inst->no_of_words = NO_OF_WORDS_30MS; - iLBCdec_inst->state_short_len=STATE_SHORT_LEN_30MS; - /* ULP init */ - iLBCdec_inst->ULP_inst=&ULP_30msTbl; - } - else if (mode==20) { - iLBCdec_inst->blockl = BLOCKL_20MS; - iLBCdec_inst->nsub = NSUB_20MS; - iLBCdec_inst->nasub = NASUB_20MS; - iLBCdec_inst->lpc_n = LPC_N_20MS; - iLBCdec_inst->no_of_bytes = NO_OF_BYTES_20MS; - iLBCdec_inst->no_of_words = NO_OF_WORDS_20MS; - iLBCdec_inst->state_short_len=STATE_SHORT_LEN_20MS; - /* ULP init */ - iLBCdec_inst->ULP_inst=&ULP_20msTbl; - } - else { - exit(2); - } - - memset(iLBCdec_inst->syntMem, 0, - LPC_FILTERORDER*sizeof(float)); - memcpy((*iLBCdec_inst).lsfdeqold, lsfmeanTbl, - LPC_FILTERORDER*sizeof(float)); - - memset(iLBCdec_inst->old_syntdenum, 0, - ((LPC_FILTERORDER + 1)*NSUB_MAX)*sizeof(float)); - for (i=0; iold_syntdenum[i*(LPC_FILTERORDER+1)]=1.0; - - iLBCdec_inst->last_lag = 20; - - iLBCdec_inst->prevLag = 120; - iLBCdec_inst->per = 0.0; - iLBCdec_inst->consPLICount = 0; - iLBCdec_inst->prevPLI = 0; - iLBCdec_inst->prevLpc[0] = 1.0; - memset(iLBCdec_inst->prevLpc+1,0, - LPC_FILTERORDER*sizeof(float)); - memset(iLBCdec_inst->prevResidual, 0, BLOCKL_MAX*sizeof(float)); - iLBCdec_inst->seed=777; - - - - -Andersen, et al. Experimental [Page 65] - -RFC 3951 Internet Low Bit Rate Codec December 2004 - - - memset(iLBCdec_inst->hpomem, 0, 4*sizeof(float)); - - iLBCdec_inst->use_enhancer = use_enhancer; - memset(iLBCdec_inst->enh_buf, 0, ENH_BUFL*sizeof(float)); - for (i=0;ienh_period[i]=(float)40.0; - - iLBCdec_inst->prev_enh_pl = 0; - - return (iLBCdec_inst->blockl); - } - - /*----------------------------------------------------------------* - * frame residual decoder function (subrutine to iLBC_decode) - *---------------------------------------------------------------*/ - - void Decode( - iLBC_Dec_Inst_t *iLBCdec_inst, /* (i/o) the decoder state - structure */ - float *decresidual, /* (o) decoded residual frame */ - int start, /* (i) location of start - state */ - int idxForMax, /* (i) codebook index for the - maximum value */ - int *idxVec, /* (i) codebook indexes for the - samples in the start - state */ - float *syntdenum, /* (i) the decoded synthesis - filter coefficients */ - int *cb_index, /* (i) the indexes for the - adaptive codebook */ - int *gain_index, /* (i) the indexes for the - corresponding gains */ - int *extra_cb_index, /* (i) the indexes for the - adaptive codebook part - of start state */ - int *extra_gain_index, /* (i) the indexes for the - corresponding gains */ - int state_first /* (i) 1 if non adaptive part - of start state comes - first 0 if that part - comes last */ - ){ - float reverseDecresidual[BLOCKL_MAX], mem[CB_MEML]; - int k, meml_gotten, Nfor, Nback, i; - int diff, start_pos; - int subcount, subframe; - - - - -Andersen, et al. Experimental [Page 66] - -RFC 3951 Internet Low Bit Rate Codec December 2004 - - - diff = STATE_LEN - iLBCdec_inst->state_short_len; - - if (state_first == 1) { - start_pos = (start-1)*SUBL; - } else { - start_pos = (start-1)*SUBL + diff; - } - - /* decode scalar part of start state */ - - StateConstructW(idxForMax, idxVec, - &syntdenum[(start-1)*(LPC_FILTERORDER+1)], - &decresidual[start_pos], iLBCdec_inst->state_short_len); - - - if (state_first) { /* put adaptive part in the end */ - - /* setup memory */ - - memset(mem, 0, - (CB_MEML-iLBCdec_inst->state_short_len)*sizeof(float)); - memcpy(mem+CB_MEML-iLBCdec_inst->state_short_len, - decresidual+start_pos, - iLBCdec_inst->state_short_len*sizeof(float)); - - /* construct decoded vector */ - - iCBConstruct( - &decresidual[start_pos+iLBCdec_inst->state_short_len], - extra_cb_index, extra_gain_index, mem+CB_MEML-stMemLTbl, - stMemLTbl, diff, CB_NSTAGES); - - } - else {/* put adaptive part in the beginning */ - - /* create reversed vectors for prediction */ - - for (k=0; kstate_short_len)]; - } - - /* setup memory */ - - meml_gotten = iLBCdec_inst->state_short_len; - for (k=0; knsub-start-1; - - if ( Nfor > 0 ){ - - /* setup memory */ - - memset(mem, 0, (CB_MEML-STATE_LEN)*sizeof(float)); - memcpy(mem+CB_MEML-STATE_LEN, decresidual+(start-1)*SUBL, - STATE_LEN*sizeof(float)); - - /* loop over sub-frames to encode */ - - for (subframe=0; subframe 0 ) { - - /* setup memory */ - - meml_gotten = SUBL*(iLBCdec_inst->nsub+1-start); - - if ( meml_gotten > CB_MEML ) { - meml_gotten=CB_MEML; - } - for (k=0; k0) { /* the data are good */ - - /* decode data */ - - pbytes=bytes; - pos=0; - - - - -Andersen, et al. Experimental [Page 70] - -RFC 3951 Internet Low Bit Rate Codec December 2004 - - - /* Set everything to zero before decoding */ - - for (k=0; kstate_short_len; k++) { - idxVec[k]=0; - } - for (k=0; knasub; i++) { - for (k=0; knasub; i++) { - for (k=0; klpc_n; k++){ - unpack( &pbytes, &lastpart, - iLBCdec_inst->ULP_inst->lsf_bits[k][ulp], &pos); - packcombine(&lsf_i[k], lastpart, - iLBCdec_inst->ULP_inst->lsf_bits[k][ulp]); - } - - /* Start block info */ - - unpack( &pbytes, &lastpart, - iLBCdec_inst->ULP_inst->start_bits[ulp], &pos); - packcombine(&start, lastpart, - iLBCdec_inst->ULP_inst->start_bits[ulp]); - - unpack( &pbytes, &lastpart, - - - -Andersen, et al. Experimental [Page 71] - -RFC 3951 Internet Low Bit Rate Codec December 2004 - - - iLBCdec_inst->ULP_inst->startfirst_bits[ulp], &pos); - packcombine(&state_first, lastpart, - iLBCdec_inst->ULP_inst->startfirst_bits[ulp]); - - unpack( &pbytes, &lastpart, - iLBCdec_inst->ULP_inst->scale_bits[ulp], &pos); - packcombine(&idxForMax, lastpart, - iLBCdec_inst->ULP_inst->scale_bits[ulp]); - - for (k=0; kstate_short_len; k++) { - unpack( &pbytes, &lastpart, - iLBCdec_inst->ULP_inst->state_bits[ulp], &pos); - packcombine(idxVec+k, lastpart, - iLBCdec_inst->ULP_inst->state_bits[ulp]); - } - - /* 23/22 (20ms/30ms) sample block */ - - for (k=0; kULP_inst->extra_cb_index[k][ulp], - &pos); - packcombine(extra_cb_index+k, lastpart, - iLBCdec_inst->ULP_inst->extra_cb_index[k][ulp]); - } - for (k=0; kULP_inst->extra_cb_gain[k][ulp], - &pos); - packcombine(extra_gain_index+k, lastpart, - iLBCdec_inst->ULP_inst->extra_cb_gain[k][ulp]); - } - - /* The two/four (20ms/30ms) 40 sample sub-blocks */ - - for (i=0; inasub; i++) { - for (k=0; kULP_inst->cb_index[i][k][ulp], - &pos); - packcombine(cb_index+i*CB_NSTAGES+k, lastpart, - iLBCdec_inst->ULP_inst->cb_index[i][k][ulp]); - } - } - - for (i=0; inasub; i++) { - for (k=0; kULP_inst->cb_gain[i][k][ulp], - &pos); - packcombine(gain_index+i*CB_NSTAGES+k, lastpart, - iLBCdec_inst->ULP_inst->cb_gain[i][k][ulp]); - } - } - } - /* Extract last bit. If it is 1 this indicates an - empty/lost frame */ - unpack( &pbytes, &last_bit, 1, &pos); - - /* Check for bit errors or empty/lost frames */ - if (start<1) - mode = 0; - if (iLBCdec_inst->mode==20 && start>3) - mode = 0; - if (iLBCdec_inst->mode==30 && start>5) - mode = 0; - if (last_bit==1) - mode = 0; - - if (mode==1) { /* No bit errors was detected, - continue decoding */ - - /* adjust index */ - index_conv_dec(cb_index); - - /* decode the lsf */ - - SimplelsfDEQ(lsfdeq, lsf_i, iLBCdec_inst->lpc_n); - check=LSF_check(lsfdeq, LPC_FILTERORDER, - iLBCdec_inst->lpc_n); - DecoderInterpolateLSF(syntdenum, weightdenum, - lsfdeq, LPC_FILTERORDER, iLBCdec_inst); - - Decode(iLBCdec_inst, decresidual, start, idxForMax, - idxVec, syntdenum, cb_index, gain_index, - extra_cb_index, extra_gain_index, - state_first); - - /* preparing the plc for a future loss! */ - - doThePLC(PLCresidual, PLClpc, 0, decresidual, - syntdenum + - (LPC_FILTERORDER + 1)*(iLBCdec_inst->nsub - 1), - (*iLBCdec_inst).last_lag, iLBCdec_inst); - - - - - -Andersen, et al. Experimental [Page 73] - -RFC 3951 Internet Low Bit Rate Codec December 2004 - - - memcpy(decresidual, PLCresidual, - iLBCdec_inst->blockl*sizeof(float)); - } - - } - - if (mode == 0) { - /* the data is bad (either a PLC call - * was made or a severe bit error was detected) - */ - - /* packet loss conceal */ - - memset(zeros, 0, BLOCKL_MAX*sizeof(float)); - - one[0] = 1; - memset(one+1, 0, LPC_FILTERORDER*sizeof(float)); - - start=0; - - doThePLC(PLCresidual, PLClpc, 1, zeros, one, - (*iLBCdec_inst).last_lag, iLBCdec_inst); - memcpy(decresidual, PLCresidual, - iLBCdec_inst->blockl*sizeof(float)); - - order_plus_one = LPC_FILTERORDER + 1; - for (i = 0; i < iLBCdec_inst->nsub; i++) { - memcpy(syntdenum+(i*order_plus_one), PLClpc, - order_plus_one*sizeof(float)); - } - } - - if (iLBCdec_inst->use_enhancer == 1) { - - /* post filtering */ - - iLBCdec_inst->last_lag = - enhancerInterface(data, decresidual, iLBCdec_inst); - - /* synthesis filtering */ - - if (iLBCdec_inst->mode==20) { - /* Enhancer has 40 samples delay */ - i=0; - syntFilter(data + i*SUBL, - iLBCdec_inst->old_syntdenum + - (i+iLBCdec_inst->nsub-1)*(LPC_FILTERORDER+1), - SUBL, iLBCdec_inst->syntMem); - - - -Andersen, et al. Experimental [Page 74] - -RFC 3951 Internet Low Bit Rate Codec December 2004 - - - for (i=1; i < iLBCdec_inst->nsub; i++) { - syntFilter(data + i*SUBL, - syntdenum + (i-1)*(LPC_FILTERORDER+1), - SUBL, iLBCdec_inst->syntMem); - } - } else if (iLBCdec_inst->mode==30) { - /* Enhancer has 80 samples delay */ - for (i=0; i < 2; i++) { - syntFilter(data + i*SUBL, - iLBCdec_inst->old_syntdenum + - (i+iLBCdec_inst->nsub-2)*(LPC_FILTERORDER+1), - SUBL, iLBCdec_inst->syntMem); - } - for (i=2; i < iLBCdec_inst->nsub; i++) { - syntFilter(data + i*SUBL, - syntdenum + (i-2)*(LPC_FILTERORDER+1), SUBL, - iLBCdec_inst->syntMem); - } - } - - } else { - - /* Find last lag */ - lag = 20; - maxcc = xCorrCoef(&decresidual[BLOCKL_MAX-ENH_BLOCKL], - &decresidual[BLOCKL_MAX-ENH_BLOCKL-lag], ENH_BLOCKL); - - for (ilag=21; ilag<120; ilag++) { - cc = xCorrCoef(&decresidual[BLOCKL_MAX-ENH_BLOCKL], - &decresidual[BLOCKL_MAX-ENH_BLOCKL-ilag], - ENH_BLOCKL); - - if (cc > maxcc) { - maxcc = cc; - lag = ilag; - } - } - iLBCdec_inst->last_lag = lag; - - /* copy data and run synthesis filter */ - - memcpy(data, decresidual, - iLBCdec_inst->blockl*sizeof(float)); - for (i=0; i < iLBCdec_inst->nsub; i++) { - syntFilter(data + i*SUBL, - syntdenum + i*(LPC_FILTERORDER+1), SUBL, - iLBCdec_inst->syntMem); - } - - - -Andersen, et al. Experimental [Page 75] - -RFC 3951 Internet Low Bit Rate Codec December 2004 - - - } - - /* high pass filtering on output if desired, otherwise - copy to out */ - - hpOutput(data, iLBCdec_inst->blockl, - decblock,iLBCdec_inst->hpomem); - - /* memcpy(decblock,data,iLBCdec_inst->blockl*sizeof(float));*/ - - memcpy(iLBCdec_inst->old_syntdenum, syntdenum, - - iLBCdec_inst->nsub*(LPC_FILTERORDER+1)*sizeof(float)); - - iLBCdec_inst->prev_enh_pl=0; - - if (mode==0) { /* PLC was used */ - iLBCdec_inst->prev_enh_pl=1; - } - } - -A.6. iLBC_define.h - - /****************************************************************** - - iLBC Speech Coder ANSI-C Source Code - - iLBC_define.h - - Copyright (C) The Internet Society (2004). - All Rights Reserved. - - ******************************************************************/ - #include - - #ifndef __iLBC_ILBCDEFINE_H - #define __iLBC_ILBCDEFINE_H - - /* general codec settings */ - - #define FS (float)8000.0 - #define BLOCKL_20MS 160 - #define BLOCKL_30MS 240 - #define BLOCKL_MAX 240 - #define NSUB_20MS 4 - #define NSUB_30MS 6 - #define NSUB_MAX 6 - #define NASUB_20MS 2 - - - -Andersen, et al. Experimental [Page 76] - -RFC 3951 Internet Low Bit Rate Codec December 2004 - - - #define NASUB_30MS 4 - #define NASUB_MAX 4 - #define SUBL 40 - #define STATE_LEN 80 - #define STATE_SHORT_LEN_30MS 58 - #define STATE_SHORT_LEN_20MS 57 - - /* LPC settings */ - - #define LPC_FILTERORDER 10 - #define LPC_CHIRP_SYNTDENUM (float)0.9025 - #define LPC_CHIRP_WEIGHTDENUM (float)0.4222 - #define LPC_LOOKBACK 60 - #define LPC_N_20MS 1 - #define LPC_N_30MS 2 - #define LPC_N_MAX 2 - #define LPC_ASYMDIFF 20 - #define LPC_BW (float)60.0 - #define LPC_WN (float)1.0001 - #define LSF_NSPLIT 3 - #define LSF_NUMBER_OF_STEPS 4 - #define LPC_HALFORDER (LPC_FILTERORDER/2) - - /* cb settings */ - - #define CB_NSTAGES 3 - #define CB_EXPAND 2 - #define CB_MEML 147 - #define CB_FILTERLEN 2*4 - #define CB_HALFFILTERLEN 4 - #define CB_RESRANGE 34 - #define CB_MAXGAIN (float)1.3 - - /* enhancer */ - - #define ENH_BLOCKL 80 /* block length */ - #define ENH_BLOCKL_HALF (ENH_BLOCKL/2) - #define ENH_HL 3 /* 2*ENH_HL+1 is number blocks - in said second sequence */ - #define ENH_SLOP 2 /* max difference estimated and - correct pitch period */ - #define ENH_PLOCSL 20 /* pitch-estimates and pitch- - locations buffer length */ - #define ENH_OVERHANG 2 - #define ENH_UPS0 4 /* upsampling rate */ - #define ENH_FL0 3 /* 2*FLO+1 is the length of - each filter */ - #define ENH_VECTL (ENH_BLOCKL+2*ENH_FL0) - - - -Andersen, et al. Experimental [Page 77] - -RFC 3951 Internet Low Bit Rate Codec December 2004 - - - #define ENH_CORRDIM (2*ENH_SLOP+1) - #define ENH_NBLOCKS (BLOCKL_MAX/ENH_BLOCKL) - #define ENH_NBLOCKS_EXTRA 5 - #define ENH_NBLOCKS_TOT 8 /* ENH_NBLOCKS + - ENH_NBLOCKS_EXTRA */ - #define ENH_BUFL (ENH_NBLOCKS_TOT)*ENH_BLOCKL - #define ENH_ALPHA0 (float)0.05 - - /* Down sampling */ - - #define FILTERORDER_DS 7 - #define DELAY_DS 3 - #define FACTOR_DS 2 - - /* bit stream defs */ - - #define NO_OF_BYTES_20MS 38 - #define NO_OF_BYTES_30MS 50 - #define NO_OF_WORDS_20MS 19 - #define NO_OF_WORDS_30MS 25 - #define STATE_BITS 3 - #define BYTE_LEN 8 - #define ULP_CLASSES 3 - - /* help parameters */ - - #define FLOAT_MAX (float)1.0e37 - #define EPS (float)2.220446049250313e-016 - #define PI (float)3.14159265358979323846 - #define MIN_SAMPLE -32768 - #define MAX_SAMPLE 32767 - #define TWO_PI (float)6.283185307 - #define PI2 (float)0.159154943 - - /* type definition encoder instance */ - typedef struct iLBC_ULP_Inst_t_ { - int lsf_bits[6][ULP_CLASSES+2]; - int start_bits[ULP_CLASSES+2]; - int startfirst_bits[ULP_CLASSES+2]; - int scale_bits[ULP_CLASSES+2]; - int state_bits[ULP_CLASSES+2]; - int extra_cb_index[CB_NSTAGES][ULP_CLASSES+2]; - int extra_cb_gain[CB_NSTAGES][ULP_CLASSES+2]; - int cb_index[NSUB_MAX][CB_NSTAGES][ULP_CLASSES+2]; - int cb_gain[NSUB_MAX][CB_NSTAGES][ULP_CLASSES+2]; - } iLBC_ULP_Inst_t; - - /* type definition encoder instance */ - - - -Andersen, et al. Experimental [Page 78] - -RFC 3951 Internet Low Bit Rate Codec December 2004 - - - typedef struct iLBC_Enc_Inst_t_ { - - /* flag for frame size mode */ - int mode; - - /* basic parameters for different frame sizes */ - int blockl; - int nsub; - int nasub; - int no_of_bytes, no_of_words; - int lpc_n; - int state_short_len; - const iLBC_ULP_Inst_t *ULP_inst; - - /* analysis filter state */ - float anaMem[LPC_FILTERORDER]; - - /* old lsf parameters for interpolation */ - float lsfold[LPC_FILTERORDER]; - float lsfdeqold[LPC_FILTERORDER]; - - /* signal buffer for LP analysis */ - float lpc_buffer[LPC_LOOKBACK + BLOCKL_MAX]; - - /* state of input HP filter */ - float hpimem[4]; - - } iLBC_Enc_Inst_t; - - /* type definition decoder instance */ - typedef struct iLBC_Dec_Inst_t_ { - - /* flag for frame size mode */ - int mode; - - /* basic parameters for different frame sizes */ - int blockl; - int nsub; - int nasub; - int no_of_bytes, no_of_words; - int lpc_n; - int state_short_len; - const iLBC_ULP_Inst_t *ULP_inst; - - /* synthesis filter state */ - float syntMem[LPC_FILTERORDER]; - - /* old LSF for interpolation */ - - - -Andersen, et al. Experimental [Page 79] - -RFC 3951 Internet Low Bit Rate Codec December 2004 - - - float lsfdeqold[LPC_FILTERORDER]; - - /* pitch lag estimated in enhancer and used in PLC */ - int last_lag; - - /* PLC state information */ - int prevLag, consPLICount, prevPLI, prev_enh_pl; - float prevLpc[LPC_FILTERORDER+1]; - float prevResidual[NSUB_MAX*SUBL]; - float per; - unsigned long seed; - - /* previous synthesis filter parameters */ - float old_syntdenum[(LPC_FILTERORDER + 1)*NSUB_MAX]; - - /* state of output HP filter */ - float hpomem[4]; - - /* enhancer state information */ - int use_enhancer; - float enh_buf[ENH_BUFL]; - float enh_period[ENH_NBLOCKS_TOT]; - - } iLBC_Dec_Inst_t; - - #endif - -A.7. constants.h - - /****************************************************************** - - iLBC Speech Coder ANSI-C Source Code - - constants.h - - Copyright (C) The Internet Society (2004). - All Rights Reserved. - - ******************************************************************/ - - #ifndef __iLBC_CONSTANTS_H - #define __iLBC_CONSTANTS_H - - #include "iLBC_define.h" - - - /* ULP bit allocation */ - - - - -Andersen, et al. Experimental [Page 80] - -RFC 3951 Internet Low Bit Rate Codec December 2004 - - - extern const iLBC_ULP_Inst_t ULP_20msTbl; - extern const iLBC_ULP_Inst_t ULP_30msTbl; - - /* high pass filters */ - - extern float hpi_zero_coefsTbl[]; - extern float hpi_pole_coefsTbl[]; - extern float hpo_zero_coefsTbl[]; - extern float hpo_pole_coefsTbl[]; - - /* low pass filters */ - extern float lpFilt_coefsTbl[]; - - /* LPC analysis and quantization */ - - extern float lpc_winTbl[]; - extern float lpc_asymwinTbl[]; - extern float lpc_lagwinTbl[]; - extern float lsfCbTbl[]; - extern float lsfmeanTbl[]; - extern int dim_lsfCbTbl[]; - extern int size_lsfCbTbl[]; - extern float lsf_weightTbl_30ms[]; - extern float lsf_weightTbl_20ms[]; - - /* state quantization tables */ - - extern float state_sq3Tbl[]; - extern float state_frgqTbl[]; - - /* gain quantization tables */ - - extern float gain_sq3Tbl[]; - extern float gain_sq4Tbl[]; - extern float gain_sq5Tbl[]; - - /* adaptive codebook definitions */ - - extern int search_rangeTbl[5][CB_NSTAGES]; - extern int memLfTbl[]; - extern int stMemLTbl; - extern float cbfiltersTbl[CB_FILTERLEN]; - - /* enhancer definitions */ - - extern float polyphaserTbl[]; - extern float enh_plocsTbl[]; - - - - -Andersen, et al. Experimental [Page 81] - -RFC 3951 Internet Low Bit Rate Codec December 2004 - - - #endif - -A.8. constants.c - - /****************************************************************** - - iLBC Speech Coder ANSI-C Source Code - - constants.c - - Copyright (C) The Internet Society (2004). - All Rights Reserved. - - ******************************************************************/ - - #include "iLBC_define.h" - - /* ULP bit allocation */ - - /* 20 ms frame */ - - const iLBC_ULP_Inst_t ULP_20msTbl = { - /* LSF */ - { {6,0,0,0,0}, {7,0,0,0,0}, {7,0,0,0,0}, - {0,0,0,0,0}, {0,0,0,0,0}, {0,0,0,0,0}}, - /* Start state location, gain and samples */ - {2,0,0,0,0}, - {1,0,0,0,0}, - {6,0,0,0,0}, - {0,1,2,0,0}, - /* extra CB index and extra CB gain */ - {{6,0,1,0,0}, {0,0,7,0,0}, {0,0,7,0,0}}, - {{2,0,3,0,0}, {1,1,2,0,0}, {0,0,3,0,0}}, - /* CB index and CB gain */ - { {{7,0,1,0,0}, {0,0,7,0,0}, {0,0,7,0,0}}, - {{0,0,8,0,0}, {0,0,8,0,0}, {0,0,8,0,0}}, - {{0,0,0,0,0}, {0,0,0,0,0}, {0,0,0,0,0}}, - {{0,0,0,0,0}, {0,0,0,0,0}, {0,0,0,0,0}}}, - { {{1,2,2,0,0}, {1,1,2,0,0}, {0,0,3,0,0}}, - {{1,1,3,0,0}, {0,2,2,0,0}, {0,0,3,0,0}}, - {{0,0,0,0,0}, {0,0,0,0,0}, {0,0,0,0,0}}, - {{0,0,0,0,0}, {0,0,0,0,0}, {0,0,0,0,0}}} - }; - - /* 30 ms frame */ - - const iLBC_ULP_Inst_t ULP_30msTbl = { - /* LSF */ - - - -Andersen, et al. Experimental [Page 82] - -RFC 3951 Internet Low Bit Rate Codec December 2004 - - - { {6,0,0,0,0}, {7,0,0,0,0}, {7,0,0,0,0}, - {6,0,0,0,0}, {7,0,0,0,0}, {7,0,0,0,0}}, - /* Start state location, gain and samples */ - {3,0,0,0,0}, - {1,0,0,0,0}, - {6,0,0,0,0}, - {0,1,2,0,0}, - /* extra CB index and extra CB gain */ - {{4,2,1,0,0}, {0,0,7,0,0}, {0,0,7,0,0}}, - {{1,1,3,0,0}, {1,1,2,0,0}, {0,0,3,0,0}}, - /* CB index and CB gain */ - { {{6,1,1,0,0}, {0,0,7,0,0}, {0,0,7,0,0}}, - {{0,7,1,0,0}, {0,0,8,0,0}, {0,0,8,0,0}}, - {{0,7,1,0,0}, {0,0,8,0,0}, {0,0,8,0,0}}, - {{0,7,1,0,0}, {0,0,8,0,0}, {0,0,8,0,0}}}, - { {{1,2,2,0,0}, {1,2,1,0,0}, {0,0,3,0,0}}, - {{0,2,3,0,0}, {0,2,2,0,0}, {0,0,3,0,0}}, - {{0,1,4,0,0}, {0,1,3,0,0}, {0,0,3,0,0}}, - {{0,1,4,0,0}, {0,1,3,0,0}, {0,0,3,0,0}}} - }; - - /* HP Filters */ - - float hpi_zero_coefsTbl[3] = { - (float)0.92727436, (float)-1.8544941, (float)0.92727436 - }; - float hpi_pole_coefsTbl[3] = { - (float)1.0, (float)-1.9059465, (float)0.9114024 - }; - float hpo_zero_coefsTbl[3] = { - (float)0.93980581, (float)-1.8795834, (float)0.93980581 - }; - float hpo_pole_coefsTbl[3] = { - (float)1.0, (float)-1.9330735, (float)0.93589199 - }; - - /* LP Filter */ - - float lpFilt_coefsTbl[FILTERORDER_DS]={ - (float)-0.066650, (float)0.125000, (float)0.316650, - (float)0.414063, (float)0.316650, - (float)0.125000, (float)-0.066650 - }; - - /* State quantization tables */ - - float state_sq3Tbl[8] = { - (float)-3.719849, (float)-2.177490, (float)-1.130005, - - - -Andersen, et al. Experimental [Page 83] - -RFC 3951 Internet Low Bit Rate Codec December 2004 - - - (float)-0.309692, (float)0.444214, (float)1.329712, - (float)2.436279, (float)3.983887 - }; - - float state_frgqTbl[64] = { - (float)1.000085, (float)1.071695, (float)1.140395, - (float)1.206868, (float)1.277188, (float)1.351503, - (float)1.429380, (float)1.500727, (float)1.569049, - (float)1.639599, (float)1.707071, (float)1.781531, - (float)1.840799, (float)1.901550, (float)1.956695, - (float)2.006750, (float)2.055474, (float)2.102787, - (float)2.142819, (float)2.183592, (float)2.217962, - (float)2.257177, (float)2.295739, (float)2.332967, - (float)2.369248, (float)2.402792, (float)2.435080, - (float)2.468598, (float)2.503394, (float)2.539284, - (float)2.572944, (float)2.605036, (float)2.636331, - (float)2.668939, (float)2.698780, (float)2.729101, - (float)2.759786, (float)2.789834, (float)2.818679, - (float)2.848074, (float)2.877470, (float)2.906899, - (float)2.936655, (float)2.967804, (float)3.000115, - (float)3.033367, (float)3.066355, (float)3.104231, - (float)3.141499, (float)3.183012, (float)3.222952, - (float)3.265433, (float)3.308441, (float)3.350823, - (float)3.395275, (float)3.442793, (float)3.490801, - (float)3.542514, (float)3.604064, (float)3.666050, - (float)3.740994, (float)3.830749, (float)3.938770, - (float)4.101764 - }; - - /* CB tables */ - - int search_rangeTbl[5][CB_NSTAGES]={{58,58,58}, {108,44,44}, - {108,108,108}, {108,108,108}, {108,108,108}}; - int stMemLTbl=85; - int memLfTbl[NASUB_MAX]={147,147,147,147}; - - /* expansion filter(s) */ - - float cbfiltersTbl[CB_FILTERLEN]={ - (float)-0.034180, (float)0.108887, (float)-0.184326, - (float)0.806152, (float)0.713379, (float)-0.144043, - (float)0.083740, (float)-0.033691 - }; - - /* Gain Quantization */ - - float gain_sq3Tbl[8]={ - (float)-1.000000, (float)-0.659973, (float)-0.330017, - - - -Andersen, et al. Experimental [Page 84] - -RFC 3951 Internet Low Bit Rate Codec December 2004 - - - (float)0.000000, (float)0.250000, (float)0.500000, - (float)0.750000, (float)1.00000}; - - float gain_sq4Tbl[16]={ - (float)-1.049988, (float)-0.900024, (float)-0.750000, - (float)-0.599976, (float)-0.450012, (float)-0.299988, - (float)-0.150024, (float)0.000000, (float)0.150024, - (float)0.299988, (float)0.450012, (float)0.599976, - (float)0.750000, (float)0.900024, (float)1.049988, - (float)1.200012}; - - float gain_sq5Tbl[32]={ - (float)0.037476, (float)0.075012, (float)0.112488, - (float)0.150024, (float)0.187500, (float)0.224976, - (float)0.262512, (float)0.299988, (float)0.337524, - (float)0.375000, (float)0.412476, (float)0.450012, - (float)0.487488, (float)0.525024, (float)0.562500, - (float)0.599976, (float)0.637512, (float)0.674988, - (float)0.712524, (float)0.750000, (float)0.787476, - (float)0.825012, (float)0.862488, (float)0.900024, - (float)0.937500, (float)0.974976, (float)1.012512, - (float)1.049988, (float)1.087524, (float)1.125000, - (float)1.162476, (float)1.200012}; - - /* Enhancer - Upsamling a factor 4 (ENH_UPS0 = 4) */ - float polyphaserTbl[ENH_UPS0*(2*ENH_FL0+1)]={ - (float)0.000000, (float)0.000000, (float)0.000000, - (float)1.000000, - (float)0.000000, (float)0.000000, (float)0.000000, - (float)0.015625, (float)-0.076904, (float)0.288330, - (float)0.862061, - (float)-0.106445, (float)0.018799, (float)-0.015625, - (float)0.023682, (float)-0.124268, (float)0.601563, - (float)0.601563, - (float)-0.124268, (float)0.023682, (float)-0.023682, - (float)0.018799, (float)-0.106445, (float)0.862061, - (float)0.288330, - (float)-0.076904, (float)0.015625, (float)-0.018799}; - - float enh_plocsTbl[ENH_NBLOCKS_TOT] = {(float)40.0, (float)120.0, - (float)200.0, (float)280.0, (float)360.0, - (float)440.0, (float)520.0, (float)600.0}; - - /* LPC analysis and quantization */ - - int dim_lsfCbTbl[LSF_NSPLIT] = {3, 3, 4}; - int size_lsfCbTbl[LSF_NSPLIT] = {64,128,128}; - - - - -Andersen, et al. Experimental [Page 85] - -RFC 3951 Internet Low Bit Rate Codec December 2004 - - - float lsfmeanTbl[LPC_FILTERORDER] = { - (float)0.281738, (float)0.445801, (float)0.663330, - (float)0.962524, (float)1.251831, (float)1.533081, - (float)1.850586, (float)2.137817, (float)2.481445, - (float)2.777344}; - - float lsf_weightTbl_30ms[6] = {(float)(1.0/2.0), (float)1.0, - (float)(2.0/3.0), - (float)(1.0/3.0), (float)0.0, (float)0.0}; - - float lsf_weightTbl_20ms[4] = {(float)(3.0/4.0), (float)(2.0/4.0), - (float)(1.0/4.0), (float)(0.0)}; - - /* Hanning LPC window */ - float lpc_winTbl[BLOCKL_MAX]={ - (float)0.000183, (float)0.000671, (float)0.001526, - (float)0.002716, (float)0.004242, (float)0.006104, - (float)0.008301, (float)0.010834, (float)0.013702, - (float)0.016907, (float)0.020416, (float)0.024261, - (float)0.028442, (float)0.032928, (float)0.037750, - (float)0.042877, (float)0.048309, (float)0.054047, - (float)0.060089, (float)0.066437, (float)0.073090, - (float)0.080017, (float)0.087219, (float)0.094727, - (float)0.102509, (float)0.110535, (float)0.118835, - (float)0.127411, (float)0.136230, (float)0.145294, - (float)0.154602, (float)0.164154, (float)0.173920, - (float)0.183899, (float)0.194122, (float)0.204529, - (float)0.215149, (float)0.225952, (float)0.236938, - (float)0.248108, (float)0.259460, (float)0.270966, - (float)0.282654, (float)0.294464, (float)0.306396, - (float)0.318481, (float)0.330688, (float)0.343018, - (float)0.355438, (float)0.367981, (float)0.380585, - (float)0.393280, (float)0.406067, (float)0.418884, - (float)0.431763, (float)0.444702, (float)0.457672, - (float)0.470673, (float)0.483704, (float)0.496735, - (float)0.509766, (float)0.522797, (float)0.535828, - (float)0.548798, (float)0.561768, (float)0.574677, - (float)0.587524, (float)0.600342, (float)0.613068, - (float)0.625732, (float)0.638306, (float)0.650787, - (float)0.663147, (float)0.675415, (float)0.687561, - (float)0.699585, (float)0.711487, (float)0.723206, - (float)0.734802, (float)0.746216, (float)0.757477, - (float)0.768585, (float)0.779480, (float)0.790192, - (float)0.800720, (float)0.811005, (float)0.821106, - (float)0.830994, (float)0.840668, (float)0.850067, - (float)0.859253, (float)0.868225, (float)0.876892, - (float)0.885345, (float)0.893524, (float)0.901428, - (float)0.909058, (float)0.916412, (float)0.923492, - - - -Andersen, et al. Experimental [Page 86] - -RFC 3951 Internet Low Bit Rate Codec December 2004 - - - (float)0.930267, (float)0.936768, (float)0.942963, - (float)0.948853, (float)0.954437, (float)0.959717, - (float)0.964691, (float)0.969360, (float)0.973694, - (float)0.977692, (float)0.981384, (float)0.984741, - (float)0.987762, (float)0.990479, (float)0.992828, - (float)0.994873, (float)0.996552, (float)0.997925, - (float)0.998932, (float)0.999603, (float)0.999969, - (float)0.999969, (float)0.999603, (float)0.998932, - (float)0.997925, (float)0.996552, (float)0.994873, - (float)0.992828, (float)0.990479, (float)0.987762, - (float)0.984741, (float)0.981384, (float)0.977692, - (float)0.973694, (float)0.969360, (float)0.964691, - (float)0.959717, (float)0.954437, (float)0.948853, - (float)0.942963, (float)0.936768, (float)0.930267, - (float)0.923492, (float)0.916412, (float)0.909058, - (float)0.901428, (float)0.893524, (float)0.885345, - (float)0.876892, (float)0.868225, (float)0.859253, - (float)0.850067, (float)0.840668, (float)0.830994, - (float)0.821106, (float)0.811005, (float)0.800720, - (float)0.790192, (float)0.779480, (float)0.768585, - (float)0.757477, (float)0.746216, (float)0.734802, - (float)0.723206, (float)0.711487, (float)0.699585, - (float)0.687561, (float)0.675415, (float)0.663147, - (float)0.650787, (float)0.638306, (float)0.625732, - (float)0.613068, (float)0.600342, (float)0.587524, - (float)0.574677, (float)0.561768, (float)0.548798, - (float)0.535828, (float)0.522797, (float)0.509766, - (float)0.496735, (float)0.483704, (float)0.470673, - (float)0.457672, (float)0.444702, (float)0.431763, - (float)0.418884, (float)0.406067, (float)0.393280, - (float)0.380585, (float)0.367981, (float)0.355438, - (float)0.343018, (float)0.330688, (float)0.318481, - (float)0.306396, (float)0.294464, (float)0.282654, - (float)0.270966, (float)0.259460, (float)0.248108, - (float)0.236938, (float)0.225952, (float)0.215149, - (float)0.204529, (float)0.194122, (float)0.183899, - (float)0.173920, (float)0.164154, (float)0.154602, - (float)0.145294, (float)0.136230, (float)0.127411, - (float)0.118835, (float)0.110535, (float)0.102509, - (float)0.094727, (float)0.087219, (float)0.080017, - (float)0.073090, (float)0.066437, (float)0.060089, - (float)0.054047, (float)0.048309, (float)0.042877, - (float)0.037750, (float)0.032928, (float)0.028442, - (float)0.024261, (float)0.020416, (float)0.016907, - (float)0.013702, (float)0.010834, (float)0.008301, - (float)0.006104, (float)0.004242, (float)0.002716, - (float)0.001526, (float)0.000671, (float)0.000183 - }; - - - -Andersen, et al. Experimental [Page 87] - -RFC 3951 Internet Low Bit Rate Codec December 2004 - - - /* Asymmetric LPC window */ - float lpc_asymwinTbl[BLOCKL_MAX]={ - (float)0.000061, (float)0.000214, (float)0.000458, - (float)0.000824, (float)0.001282, (float)0.001831, - (float)0.002472, (float)0.003235, (float)0.004120, - (float)0.005066, (float)0.006134, (float)0.007294, - (float)0.008545, (float)0.009918, (float)0.011383, - (float)0.012939, (float)0.014587, (float)0.016357, - (float)0.018219, (float)0.020172, (float)0.022217, - (float)0.024353, (float)0.026611, (float)0.028961, - (float)0.031372, (float)0.033905, (float)0.036530, - (float)0.039276, (float)0.042084, (float)0.044983, - (float)0.047974, (float)0.051086, (float)0.054260, - (float)0.057526, (float)0.060883, (float)0.064331, - (float)0.067871, (float)0.071503, (float)0.075226, - (float)0.079010, (float)0.082916, (float)0.086884, - (float)0.090942, (float)0.095062, (float)0.099304, - (float)0.103607, (float)0.107971, (float)0.112427, - (float)0.116974, (float)0.121582, (float)0.126282, - (float)0.131073, (float)0.135895, (float)0.140839, - (float)0.145813, (float)0.150879, (float)0.156006, - (float)0.161224, (float)0.166504, (float)0.171844, - (float)0.177246, (float)0.182709, (float)0.188263, - (float)0.193848, (float)0.199524, (float)0.205231, - (float)0.211029, (float)0.216858, (float)0.222778, - (float)0.228729, (float)0.234741, (float)0.240814, - (float)0.246918, (float)0.253082, (float)0.259308, - (float)0.265564, (float)0.271881, (float)0.278259, - (float)0.284668, (float)0.291107, (float)0.297607, - (float)0.304138, (float)0.310730, (float)0.317322, - (float)0.323975, (float)0.330658, (float)0.337372, - (float)0.344147, (float)0.350922, (float)0.357727, - (float)0.364594, (float)0.371460, (float)0.378357, - (float)0.385284, (float)0.392212, (float)0.399170, - (float)0.406158, (float)0.413177, (float)0.420197, - (float)0.427246, (float)0.434296, (float)0.441376, - (float)0.448456, (float)0.455536, (float)0.462646, - (float)0.469757, (float)0.476868, (float)0.483978, - (float)0.491089, (float)0.498230, (float)0.505341, - (float)0.512451, (float)0.519592, (float)0.526703, - (float)0.533813, (float)0.540924, (float)0.548004, - (float)0.555084, (float)0.562164, (float)0.569244, - (float)0.576294, (float)0.583313, (float)0.590332, - (float)0.597321, (float)0.604309, (float)0.611267, - (float)0.618195, (float)0.625092, (float)0.631989, - (float)0.638855, (float)0.645660, (float)0.652466, - (float)0.659241, (float)0.665985, (float)0.672668, - (float)0.679352, (float)0.685974, (float)0.692566, - - - -Andersen, et al. Experimental [Page 88] - -RFC 3951 Internet Low Bit Rate Codec December 2004 - - - (float)0.699127, (float)0.705658, (float)0.712128, - (float)0.718536, (float)0.724945, (float)0.731262, - (float)0.737549, (float)0.743805, (float)0.750000, - (float)0.756134, (float)0.762238, (float)0.768280, - (float)0.774261, (float)0.780182, (float)0.786072, - (float)0.791870, (float)0.797638, (float)0.803314, - (float)0.808960, (float)0.814514, (float)0.820038, - (float)0.825470, (float)0.830841, (float)0.836151, - (float)0.841400, (float)0.846558, (float)0.851654, - (float)0.856689, (float)0.861633, (float)0.866516, - (float)0.871338, (float)0.876068, (float)0.880737, - (float)0.885315, (float)0.889801, (float)0.894226, - (float)0.898560, (float)0.902832, (float)0.907013, - (float)0.911102, (float)0.915100, (float)0.919037, - (float)0.922882, (float)0.926636, (float)0.930328, - (float)0.933899, (float)0.937408, (float)0.940796, - (float)0.944122, (float)0.947357, (float)0.950470, - (float)0.953522, (float)0.956482, (float)0.959351, - (float)0.962097, (float)0.964783, (float)0.967377, - (float)0.969849, (float)0.972229, (float)0.974518, - (float)0.976715, (float)0.978821, (float)0.980835, - (float)0.982727, (float)0.984528, (float)0.986237, - (float)0.987854, (float)0.989380, (float)0.990784, - (float)0.992096, (float)0.993317, (float)0.994415, - (float)0.995422, (float)0.996338, (float)0.997162, - (float)0.997864, (float)0.998474, (float)0.998962, - (float)0.999390, (float)0.999695, (float)0.999878, - (float)0.999969, (float)0.999969, (float)0.996918, - (float)0.987701, (float)0.972382, (float)0.951050, - (float)0.923889, (float)0.891022, (float)0.852631, - (float)0.809021, (float)0.760406, (float)0.707092, - (float)0.649445, (float)0.587799, (float)0.522491, - (float)0.453979, (float)0.382690, (float)0.309021, - (float)0.233459, (float)0.156433, (float)0.078461 - }; - - /* Lag window for LPC */ - float lpc_lagwinTbl[LPC_FILTERORDER + 1]={ - (float)1.000100, (float)0.998890, (float)0.995569, - (float)0.990057, (float)0.982392, - (float)0.972623, (float)0.960816, (float)0.947047, - (float)0.931405, (float)0.913989, (float)0.894909}; - - /* LSF quantization*/ - float lsfCbTbl[64 * 3 + 128 * 3 + 128 * 4] = { - (float)0.155396, (float)0.273193, (float)0.451172, - (float)0.390503, (float)0.648071, (float)1.002075, - (float)0.440186, (float)0.692261, (float)0.955688, - - - -Andersen, et al. Experimental [Page 89] - -RFC 3951 Internet Low Bit Rate Codec December 2004 - - - (float)0.343628, (float)0.642334, (float)1.071533, - (float)0.318359, (float)0.491577, (float)0.670532, - (float)0.193115, (float)0.375488, (float)0.725708, - (float)0.364136, (float)0.510376, (float)0.658691, - (float)0.297485, (float)0.527588, (float)0.842529, - (float)0.227173, (float)0.365967, (float)0.563110, - (float)0.244995, (float)0.396729, (float)0.636475, - (float)0.169434, (float)0.300171, (float)0.520264, - (float)0.312866, (float)0.464478, (float)0.643188, - (float)0.248535, (float)0.429932, (float)0.626099, - (float)0.236206, (float)0.491333, (float)0.817139, - (float)0.334961, (float)0.625122, (float)0.895752, - (float)0.343018, (float)0.518555, (float)0.698608, - (float)0.372803, (float)0.659790, (float)0.945435, - (float)0.176880, (float)0.316528, (float)0.581421, - (float)0.416382, (float)0.625977, (float)0.805176, - (float)0.303223, (float)0.568726, (float)0.915039, - (float)0.203613, (float)0.351440, (float)0.588135, - (float)0.221191, (float)0.375000, (float)0.614746, - (float)0.199951, (float)0.323364, (float)0.476074, - (float)0.300781, (float)0.433350, (float)0.566895, - (float)0.226196, (float)0.354004, (float)0.507568, - (float)0.300049, (float)0.508179, (float)0.711670, - (float)0.312012, (float)0.492676, (float)0.763428, - (float)0.329956, (float)0.541016, (float)0.795776, - (float)0.373779, (float)0.604614, (float)0.928833, - (float)0.210571, (float)0.452026, (float)0.755249, - (float)0.271118, (float)0.473267, (float)0.662476, - (float)0.285522, (float)0.436890, (float)0.634399, - (float)0.246704, (float)0.565552, (float)0.859009, - (float)0.270508, (float)0.406250, (float)0.553589, - (float)0.361450, (float)0.578491, (float)0.813843, - (float)0.342651, (float)0.482788, (float)0.622437, - (float)0.340332, (float)0.549438, (float)0.743164, - (float)0.200439, (float)0.336304, (float)0.540894, - (float)0.407837, (float)0.644775, (float)0.895142, - (float)0.294678, (float)0.454834, (float)0.699097, - (float)0.193115, (float)0.344482, (float)0.643188, - (float)0.275757, (float)0.420776, (float)0.598755, - (float)0.380493, (float)0.608643, (float)0.861084, - (float)0.222778, (float)0.426147, (float)0.676514, - (float)0.407471, (float)0.700195, (float)1.053101, - (float)0.218384, (float)0.377197, (float)0.669922, - (float)0.313232, (float)0.454102, (float)0.600952, - (float)0.347412, (float)0.571533, (float)0.874146, - (float)0.238037, (float)0.405396, (float)0.729492, - (float)0.223877, (float)0.412964, (float)0.822021, - (float)0.395264, (float)0.582153, (float)0.743896, - - - -Andersen, et al. Experimental [Page 90] - -RFC 3951 Internet Low Bit Rate Codec December 2004 - - - (float)0.247925, (float)0.485596, (float)0.720581, - (float)0.229126, (float)0.496582, (float)0.907715, - (float)0.260132, (float)0.566895, (float)1.012695, - (float)0.337402, (float)0.611572, (float)0.978149, - (float)0.267822, (float)0.447632, (float)0.769287, - (float)0.250610, (float)0.381714, (float)0.530029, - (float)0.430054, (float)0.805054, (float)1.221924, - (float)0.382568, (float)0.544067, (float)0.701660, - (float)0.383545, (float)0.710327, (float)1.149170, - (float)0.271362, (float)0.529053, (float)0.775513, - (float)0.246826, (float)0.393555, (float)0.588623, - (float)0.266846, (float)0.422119, (float)0.676758, - (float)0.311523, (float)0.580688, (float)0.838623, - (float)1.331177, (float)1.576782, (float)1.779541, - (float)1.160034, (float)1.401978, (float)1.768188, - (float)1.161865, (float)1.525146, (float)1.715332, - (float)0.759521, (float)0.913940, (float)1.119873, - (float)0.947144, (float)1.121338, (float)1.282471, - (float)1.015015, (float)1.557007, (float)1.804932, - (float)1.172974, (float)1.402100, (float)1.692627, - (float)1.087524, (float)1.474243, (float)1.665405, - (float)0.899536, (float)1.105225, (float)1.406250, - (float)1.148438, (float)1.484741, (float)1.796265, - (float)0.785645, (float)1.209839, (float)1.567749, - (float)0.867798, (float)1.166504, (float)1.450684, - (float)0.922485, (float)1.229858, (float)1.420898, - (float)0.791260, (float)1.123291, (float)1.409546, - (float)0.788940, (float)0.966064, (float)1.340332, - (float)1.051147, (float)1.272827, (float)1.556641, - (float)0.866821, (float)1.181152, (float)1.538818, - (float)0.906738, (float)1.373535, (float)1.607910, - (float)1.244751, (float)1.581421, (float)1.933838, - (float)0.913940, (float)1.337280, (float)1.539673, - (float)0.680542, (float)0.959229, (float)1.662720, - (float)0.887207, (float)1.430542, (float)1.800781, - (float)0.912598, (float)1.433594, (float)1.683960, - (float)0.860474, (float)1.060303, (float)1.455322, - (float)1.005127, (float)1.381104, (float)1.706909, - (float)0.800781, (float)1.363892, (float)1.829102, - (float)0.781860, (float)1.124390, (float)1.505981, - (float)1.003662, (float)1.471436, (float)1.684692, - (float)0.981323, (float)1.309570, (float)1.618042, - (float)1.228760, (float)1.554321, (float)1.756470, - (float)0.734375, (float)0.895752, (float)1.225586, - (float)0.841797, (float)1.055664, (float)1.249268, - (float)0.920166, (float)1.119385, (float)1.486206, - (float)0.894409, (float)1.539063, (float)1.828979, - (float)1.283691, (float)1.543335, (float)1.858276, - - - -Andersen, et al. Experimental [Page 91] - -RFC 3951 Internet Low Bit Rate Codec December 2004 - - - (float)0.676025, (float)0.933105, (float)1.490845, - (float)0.821289, (float)1.491821, (float)1.739868, - (float)0.923218, (float)1.144653, (float)1.580566, - (float)1.057251, (float)1.345581, (float)1.635864, - (float)0.888672, (float)1.074951, (float)1.353149, - (float)0.942749, (float)1.195435, (float)1.505493, - (float)1.492310, (float)1.788086, (float)2.039673, - (float)1.070313, (float)1.634399, (float)1.860962, - (float)1.253296, (float)1.488892, (float)1.686035, - (float)0.647095, (float)0.864014, (float)1.401855, - (float)0.866699, (float)1.254883, (float)1.453369, - (float)1.063965, (float)1.532593, (float)1.731323, - (float)1.167847, (float)1.521484, (float)1.884033, - (float)0.956055, (float)1.502075, (float)1.745605, - (float)0.928711, (float)1.288574, (float)1.479614, - (float)1.088013, (float)1.380737, (float)1.570801, - (float)0.905029, (float)1.186768, (float)1.371948, - (float)1.057861, (float)1.421021, (float)1.617432, - (float)1.108276, (float)1.312500, (float)1.501465, - (float)0.979492, (float)1.416992, (float)1.624268, - (float)1.276001, (float)1.661011, (float)2.007935, - (float)0.993042, (float)1.168579, (float)1.331665, - (float)0.778198, (float)0.944946, (float)1.235962, - (float)1.223755, (float)1.491333, (float)1.815674, - (float)0.852661, (float)1.350464, (float)1.722290, - (float)1.134766, (float)1.593140, (float)1.787354, - (float)1.051392, (float)1.339722, (float)1.531006, - (float)0.803589, (float)1.271240, (float)1.652100, - (float)0.755737, (float)1.143555, (float)1.639404, - (float)0.700928, (float)0.837280, (float)1.130371, - (float)0.942749, (float)1.197876, (float)1.669800, - (float)0.993286, (float)1.378296, (float)1.566528, - (float)0.801025, (float)1.095337, (float)1.298950, - (float)0.739990, (float)1.032959, (float)1.383667, - (float)0.845703, (float)1.072266, (float)1.543823, - (float)0.915649, (float)1.072266, (float)1.224487, - (float)1.021973, (float)1.226196, (float)1.481323, - (float)0.999878, (float)1.204102, (float)1.555908, - (float)0.722290, (float)0.913940, (float)1.340210, - (float)0.673340, (float)0.835938, (float)1.259521, - (float)0.832397, (float)1.208374, (float)1.394165, - (float)0.962158, (float)1.576172, (float)1.912842, - (float)1.166748, (float)1.370850, (float)1.556763, - (float)0.946289, (float)1.138550, (float)1.400391, - (float)1.035034, (float)1.218262, (float)1.386475, - (float)1.393799, (float)1.717773, (float)2.000244, - (float)0.972656, (float)1.260986, (float)1.760620, - (float)1.028198, (float)1.288452, (float)1.484619, - - - -Andersen, et al. Experimental [Page 92] - -RFC 3951 Internet Low Bit Rate Codec December 2004 - - - (float)0.773560, (float)1.258057, (float)1.756714, - (float)1.080322, (float)1.328003, (float)1.742676, - (float)0.823975, (float)1.450806, (float)1.917725, - (float)0.859009, (float)1.016602, (float)1.191895, - (float)0.843994, (float)1.131104, (float)1.645020, - (float)1.189697, (float)1.702759, (float)1.894409, - (float)1.346680, (float)1.763184, (float)2.066040, - (float)0.980469, (float)1.253784, (float)1.441650, - (float)1.338135, (float)1.641968, (float)1.932739, - (float)1.223267, (float)1.424194, (float)1.626465, - (float)0.765747, (float)1.004150, (float)1.579102, - (float)1.042847, (float)1.269165, (float)1.647461, - (float)0.968750, (float)1.257568, (float)1.555786, - (float)0.826294, (float)0.993408, (float)1.275146, - (float)0.742310, (float)0.950439, (float)1.430542, - (float)1.054321, (float)1.439819, (float)1.828003, - (float)1.072998, (float)1.261719, (float)1.441895, - (float)0.859375, (float)1.036377, (float)1.314819, - (float)0.895752, (float)1.267212, (float)1.605591, - (float)0.805420, (float)0.962891, (float)1.142334, - (float)0.795654, (float)1.005493, (float)1.468506, - (float)1.105347, (float)1.313843, (float)1.584839, - (float)0.792236, (float)1.221802, (float)1.465698, - (float)1.170532, (float)1.467651, (float)1.664063, - (float)0.838257, (float)1.153198, (float)1.342163, - (float)0.968018, (float)1.198242, (float)1.391235, - (float)1.250122, (float)1.623535, (float)1.823608, - (float)0.711670, (float)1.058350, (float)1.512085, - (float)1.204834, (float)1.454468, (float)1.739136, - (float)1.137451, (float)1.421753, (float)1.620117, - (float)0.820435, (float)1.322754, (float)1.578247, - (float)0.798706, (float)1.005005, (float)1.213867, - (float)0.980713, (float)1.324951, (float)1.512939, - (float)1.112305, (float)1.438843, (float)1.735596, - (float)1.135498, (float)1.356689, (float)1.635742, - (float)1.101318, (float)1.387451, (float)1.686523, - (float)0.849854, (float)1.276978, (float)1.523438, - (float)1.377930, (float)1.627563, (float)1.858154, - (float)0.884888, (float)1.095459, (float)1.287476, - (float)1.289795, (float)1.505859, (float)1.756592, - (float)0.817505, (float)1.384155, (float)1.650513, - (float)1.446655, (float)1.702148, (float)1.931885, - (float)0.835815, (float)1.023071, (float)1.385376, - (float)0.916626, (float)1.139038, (float)1.335327, - (float)0.980103, (float)1.174072, (float)1.453735, - (float)1.705688, (float)2.153809, (float)2.398315, (float)2.743408, - (float)1.797119, (float)2.016846, (float)2.445679, (float)2.701904, - (float)1.990356, (float)2.219116, (float)2.576416, (float)2.813477, - - - -Andersen, et al. Experimental [Page 93] - -RFC 3951 Internet Low Bit Rate Codec December 2004 - - - (float)1.849365, (float)2.190918, (float)2.611572, (float)2.835083, - (float)1.657959, (float)1.854370, (float)2.159058, (float)2.726196, - (float)1.437744, (float)1.897705, (float)2.253174, (float)2.655396, - (float)2.028687, (float)2.247314, (float)2.542358, (float)2.875854, - (float)1.736938, (float)1.922119, (float)2.185913, (float)2.743408, - (float)1.521606, (float)1.870972, (float)2.526855, (float)2.786987, - (float)1.841431, (float)2.050659, (float)2.463623, (float)2.857666, - (float)1.590088, (float)2.067261, (float)2.427979, (float)2.794434, - (float)1.746826, (float)2.057373, (float)2.320190, (float)2.800781, - (float)1.734619, (float)1.940552, (float)2.306030, (float)2.826416, - (float)1.786255, (float)2.204468, (float)2.457520, (float)2.795288, - (float)1.861084, (float)2.170532, (float)2.414551, (float)2.763672, - (float)2.001465, (float)2.307617, (float)2.552734, (float)2.811890, - (float)1.784424, (float)2.124146, (float)2.381592, (float)2.645508, - (float)1.888794, (float)2.135864, (float)2.418579, (float)2.861206, - (float)2.301147, (float)2.531250, (float)2.724976, (float)2.913086, - (float)1.837769, (float)2.051270, (float)2.261963, (float)2.553223, - (float)2.012939, (float)2.221191, (float)2.440186, (float)2.678101, - (float)1.429565, (float)1.858276, (float)2.582275, (float)2.845703, - (float)1.622803, (float)1.897705, (float)2.367310, (float)2.621094, - (float)1.581543, (float)1.960449, (float)2.515869, (float)2.736450, - (float)1.419434, (float)1.933960, (float)2.394653, (float)2.746704, - (float)1.721924, (float)2.059570, (float)2.421753, (float)2.769653, - (float)1.911011, (float)2.220703, (float)2.461060, (float)2.740723, - (float)1.581177, (float)1.860840, (float)2.516968, (float)2.874634, - (float)1.870361, (float)2.098755, (float)2.432373, (float)2.656494, - (float)2.059692, (float)2.279785, (float)2.495605, (float)2.729370, - (float)1.815674, (float)2.181519, (float)2.451538, (float)2.680542, - (float)1.407959, (float)1.768311, (float)2.343018, (float)2.668091, - (float)2.168701, (float)2.394653, (float)2.604736, (float)2.829346, - (float)1.636230, (float)1.865723, (float)2.329102, (float)2.824219, - (float)1.878906, (float)2.139526, (float)2.376709, (float)2.679810, - (float)1.765381, (float)1.971802, (float)2.195435, (float)2.586914, - (float)2.164795, (float)2.410889, (float)2.673706, (float)2.903198, - (float)2.071899, (float)2.331055, (float)2.645874, (float)2.907104, - (float)2.026001, (float)2.311523, (float)2.594849, (float)2.863892, - (float)1.948975, (float)2.180786, (float)2.514893, (float)2.797852, - (float)1.881836, (float)2.130859, (float)2.478149, (float)2.804199, - (float)2.238159, (float)2.452759, (float)2.652832, (float)2.868286, - (float)1.897949, (float)2.101685, (float)2.524292, (float)2.880127, - (float)1.856445, (float)2.074585, (float)2.541016, (float)2.791748, - (float)1.695557, (float)2.199097, (float)2.506226, (float)2.742676, - (float)1.612671, (float)1.877075, (float)2.435425, (float)2.732910, - (float)1.568848, (float)1.786499, (float)2.194580, (float)2.768555, - (float)1.953369, (float)2.164551, (float)2.486938, (float)2.874023, - (float)1.388306, (float)1.725342, (float)2.384521, (float)2.771851, - (float)2.115356, (float)2.337769, (float)2.592896, (float)2.864014, - (float)1.905762, (float)2.111328, (float)2.363525, (float)2.789307, - - - -Andersen, et al. Experimental [Page 94] - -RFC 3951 Internet Low Bit Rate Codec December 2004 - - - (float)1.882568, (float)2.332031, (float)2.598267, (float)2.827637, - (float)1.683594, (float)2.088745, (float)2.361938, (float)2.608643, - (float)1.874023, (float)2.182129, (float)2.536133, (float)2.766968, - (float)1.861938, (float)2.070435, (float)2.309692, (float)2.700562, - (float)1.722168, (float)2.107422, (float)2.477295, (float)2.837646, - (float)1.926880, (float)2.184692, (float)2.442627, (float)2.663818, - (float)2.123901, (float)2.337280, (float)2.553101, (float)2.777466, - (float)1.588135, (float)1.911499, (float)2.212769, (float)2.543945, - (float)2.053955, (float)2.370850, (float)2.712158, (float)2.939941, - (float)2.210449, (float)2.519653, (float)2.770386, (float)2.958618, - (float)2.199463, (float)2.474731, (float)2.718262, (float)2.919922, - (float)1.960083, (float)2.175415, (float)2.608032, (float)2.888794, - (float)1.953735, (float)2.185181, (float)2.428223, (float)2.809570, - (float)1.615234, (float)2.036499, (float)2.576538, (float)2.834595, - (float)1.621094, (float)2.028198, (float)2.431030, (float)2.664673, - (float)1.824951, (float)2.267456, (float)2.514526, (float)2.747925, - (float)1.994263, (float)2.229126, (float)2.475220, (float)2.833984, - (float)1.746338, (float)2.011353, (float)2.588257, (float)2.826904, - (float)1.562866, (float)2.135986, (float)2.471680, (float)2.687256, - (float)1.748901, (float)2.083496, (float)2.460938, (float)2.686279, - (float)1.758057, (float)2.131470, (float)2.636597, (float)2.891602, - (float)2.071289, (float)2.299072, (float)2.550781, (float)2.814331, - (float)1.839600, (float)2.094360, (float)2.496460, (float)2.723999, - (float)1.882202, (float)2.088257, (float)2.636841, (float)2.923096, - (float)1.957886, (float)2.153198, (float)2.384399, (float)2.615234, - (float)1.992920, (float)2.351196, (float)2.654419, (float)2.889771, - (float)2.012817, (float)2.262451, (float)2.643799, (float)2.903076, - (float)2.025635, (float)2.254761, (float)2.508423, (float)2.784058, - (float)2.316040, (float)2.589355, (float)2.794189, (float)2.963623, - (float)1.741211, (float)2.279541, (float)2.578491, (float)2.816284, - (float)1.845337, (float)2.055786, (float)2.348511, (float)2.822021, - (float)1.679932, (float)1.926514, (float)2.499756, (float)2.835693, - (float)1.722534, (float)1.946899, (float)2.448486, (float)2.728760, - (float)1.829834, (float)2.043213, (float)2.580444, (float)2.867676, - (float)1.676636, (float)2.071655, (float)2.322510, (float)2.704834, - (float)1.791504, (float)2.113525, (float)2.469727, (float)2.784058, - (float)1.977051, (float)2.215088, (float)2.497437, (float)2.726929, - (float)1.800171, (float)2.106689, (float)2.357788, (float)2.738892, - (float)1.827759, (float)2.170166, (float)2.525879, (float)2.852417, - (float)1.918335, (float)2.132813, (float)2.488403, (float)2.728149, - (float)1.916748, (float)2.225098, (float)2.542603, (float)2.857666, - (float)1.761230, (float)1.976074, (float)2.507446, (float)2.884521, - (float)2.053711, (float)2.367432, (float)2.608032, (float)2.837646, - (float)1.595337, (float)2.000977, (float)2.307129, (float)2.578247, - (float)1.470581, (float)2.031250, (float)2.375854, (float)2.647583, - (float)1.801392, (float)2.128052, (float)2.399780, (float)2.822876, - (float)1.853638, (float)2.066650, (float)2.429199, (float)2.751465, - (float)1.956299, (float)2.163696, (float)2.394775, (float)2.734253, - - - -Andersen, et al. Experimental [Page 95] - -RFC 3951 Internet Low Bit Rate Codec December 2004 - - - (float)1.963623, (float)2.275757, (float)2.585327, (float)2.865234, - (float)1.887451, (float)2.105469, (float)2.331787, (float)2.587402, - (float)2.120117, (float)2.443359, (float)2.733887, (float)2.941406, - (float)1.506348, (float)1.766968, (float)2.400513, (float)2.851807, - (float)1.664551, (float)1.981079, (float)2.375732, (float)2.774414, - (float)1.720703, (float)1.978882, (float)2.391479, (float)2.640991, - (float)1.483398, (float)1.814819, (float)2.434448, (float)2.722290, - (float)1.769043, (float)2.136597, (float)2.563721, (float)2.774414, - (float)1.810791, (float)2.049316, (float)2.373901, (float)2.613647, - (float)1.788330, (float)2.005981, (float)2.359131, (float)2.723145, - (float)1.785156, (float)1.993164, (float)2.399780, (float)2.832520, - (float)1.695313, (float)2.022949, (float)2.522583, (float)2.745117, - (float)1.584106, (float)1.965576, (float)2.299927, (float)2.715576, - (float)1.894897, (float)2.249878, (float)2.655884, (float)2.897705, - (float)1.720581, (float)1.995728, (float)2.299438, (float)2.557007, - (float)1.619385, (float)2.173950, (float)2.574219, (float)2.787964, - (float)1.883179, (float)2.220459, (float)2.474365, (float)2.825073, - (float)1.447632, (float)2.045044, (float)2.555542, (float)2.744873, - (float)1.502686, (float)2.156616, (float)2.653320, (float)2.846558, - (float)1.711548, (float)1.944092, (float)2.282959, (float)2.685791, - (float)1.499756, (float)1.867554, (float)2.341064, (float)2.578857, - (float)1.916870, (float)2.135132, (float)2.568237, (float)2.826050, - (float)1.498047, (float)1.711182, (float)2.223267, (float)2.755127, - (float)1.808716, (float)1.997559, (float)2.256470, (float)2.758545, - (float)2.088501, (float)2.402710, (float)2.667358, (float)2.890259, - (float)1.545044, (float)1.819214, (float)2.324097, (float)2.692993, - (float)1.796021, (float)2.012573, (float)2.505737, (float)2.784912, - (float)1.786499, (float)2.041748, (float)2.290405, (float)2.650757, - (float)1.938232, (float)2.264404, (float)2.529053, (float)2.796143 - }; - -A.9. anaFilter.h - - /****************************************************************** - - iLBC Speech Coder ANSI-C Source Code - - anaFilter.h - - Copyright (C) The Internet Society (2004). - All Rights Reserved. - - ******************************************************************/ - - #ifndef __iLBC_ANAFILTER_H - #define __iLBC_ANAFILTER_H - - void anaFilter( - - - -Andersen, et al. Experimental [Page 96] - -RFC 3951 Internet Low Bit Rate Codec December 2004 - - - float *In, /* (i) Signal to be filtered */ - float *a, /* (i) LP parameters */ - int len,/* (i) Length of signal */ - float *Out, /* (o) Filtered signal */ - float *mem /* (i/o) Filter state */ - ); - - #endif - -A.10. anaFilter.c - - /****************************************************************** - - iLBC Speech Coder ANSI-C Source Code - - anaFilter.c - - Copyright (C) The Internet Society (2004). - All Rights Reserved. - - ******************************************************************/ - - #include - #include "iLBC_define.h" - - /*----------------------------------------------------------------* - * LP analysis filter. - *---------------------------------------------------------------*/ - - void anaFilter( - float *In, /* (i) Signal to be filtered */ - float *a, /* (i) LP parameters */ - int len,/* (i) Length of signal */ - float *Out, /* (o) Filtered signal */ - float *mem /* (i/o) Filter state */ - ){ - int i, j; - float *po, *pi, *pm, *pa; - - po = Out; - - /* Filter first part using memory from past */ - - for (i=0; i - #include - - /*----------------------------------------------------------------* - * Construct an additional codebook vector by filtering the - * initial codebook buffer. This vector is then used to expand - * the codebook with an additional section. - *---------------------------------------------------------------*/ - - void filteredCBvecs( - float *cbvectors, /* (o) Codebook vectors for the - higher section */ - float *mem, /* (i) Buffer to create codebook - vector from */ - int lMem /* (i) Length of buffer */ - ){ - int j, k; - float *pp, *pp1; - float tempbuff2[CB_MEML+CB_FILTERLEN]; - float *pos; - - memset(tempbuff2, 0, (CB_HALFFILTERLEN-1)*sizeof(float)); - memcpy(&tempbuff2[CB_HALFFILTERLEN-1], mem, lMem*sizeof(float)); - memset(&tempbuff2[lMem+CB_HALFFILTERLEN-1], 0, - (CB_HALFFILTERLEN+1)*sizeof(float)); - - /* Create codebook vector for higher section by filtering */ - - /* do filtering */ - pos=cbvectors; - memset(pos, 0, lMem*sizeof(float)); - for (k=0; k0.0) { - invenergy[tmpIndex]=(float)1.0/(energy[tmpIndex]+EPS); - } else { - invenergy[tmpIndex] = (float) 0.0; - } - - if (stage==0) { - measure = (float)-10000000.0; - - if (crossDot > 0.0) { - measure = crossDot*crossDot*invenergy[tmpIndex]; - } - } - else { - measure = crossDot*crossDot*invenergy[tmpIndex]; - } - - /* check if measure is better */ - ftmp = crossDot*invenergy[tmpIndex]; - - if ((measure>*max_measure) && (fabs(ftmp) - #include - #include - - - -Andersen, et al. Experimental [Page 104] - -RFC 3951 Internet Low Bit Rate Codec December 2004 - - - #include "iLBC_define.h" - - /*----------------------------------------------------------------* - * Compute cross correlation and pitch gain for pitch prediction - * of last subframe at given lag. - *---------------------------------------------------------------*/ - - void compCorr( - float *cc, /* (o) cross correlation coefficient */ - float *gc, /* (o) gain */ - float *pm, - float *buffer, /* (i) signal buffer */ - int lag, /* (i) pitch lag */ - int bLen, /* (i) length of buffer */ - int sRange /* (i) correlation search length */ - ){ - int i; - float ftmp1, ftmp2, ftmp3; - - /* Guard against getting outside buffer */ - if ((bLen-sRange-lag)<0) { - sRange=bLen-lag; - } - - ftmp1 = 0.0; - ftmp2 = 0.0; - ftmp3 = 0.0; - for (i=0; i 0.0) { - *cc = ftmp1*ftmp1/ftmp2; - *gc = (float)fabs(ftmp1/ftmp2); - *pm=(float)fabs(ftmp1)/ - ((float)sqrt(ftmp2)*(float)sqrt(ftmp3)); - } - else { - *cc = 0.0; - *gc = 0.0; - *pm=0.0; - } - } - - - -Andersen, et al. Experimental [Page 105] - -RFC 3951 Internet Low Bit Rate Codec December 2004 - - - /*----------------------------------------------------------------* - * Packet loss concealment routine. Conceals a residual signal - * and LP parameters. If no packet loss, update state. - *---------------------------------------------------------------*/ - - void doThePLC( - float *PLCresidual, /* (o) concealed residual */ - float *PLClpc, /* (o) concealed LP parameters */ - int PLI, /* (i) packet loss indicator - 0 - no PL, 1 = PL */ - float *decresidual, /* (i) decoded residual */ - float *lpc, /* (i) decoded LPC (only used for no PL) */ - int inlag, /* (i) pitch lag */ - iLBC_Dec_Inst_t *iLBCdec_inst - /* (i/o) decoder instance */ - ){ - int lag=20, randlag; - float gain, maxcc; - float use_gain; - float gain_comp, maxcc_comp, per, max_per; - int i, pick, use_lag; - float ftmp, randvec[BLOCKL_MAX], pitchfact, energy; - - /* Packet Loss */ - - if (PLI == 1) { - - iLBCdec_inst->consPLICount += 1; - - /* if previous frame not lost, - determine pitch pred. gain */ - - if (iLBCdec_inst->prevPLI != 1) { - - /* Search around the previous lag to find the - best pitch period */ - - lag=inlag-3; - compCorr(&maxcc, &gain, &max_per, - iLBCdec_inst->prevResidual, - lag, iLBCdec_inst->blockl, 60); - for (i=inlag-2;i<=inlag+3;i++) { - compCorr(&maxcc_comp, &gain_comp, &per, - iLBCdec_inst->prevResidual, - i, iLBCdec_inst->blockl, 60); - - if (maxcc_comp>maxcc) { - maxcc=maxcc_comp; - - - -Andersen, et al. Experimental [Page 106] - -RFC 3951 Internet Low Bit Rate Codec December 2004 - - - gain=gain_comp; - lag=i; - max_per=per; - } - } - - } - - /* previous frame lost, use recorded lag and periodicity */ - - else { - lag=iLBCdec_inst->prevLag; - max_per=iLBCdec_inst->per; - } - - /* downscaling */ - - use_gain=1.0; - if (iLBCdec_inst->consPLICount*iLBCdec_inst->blockl>320) - use_gain=(float)0.9; - else if (iLBCdec_inst->consPLICount* - iLBCdec_inst->blockl>2*320) - use_gain=(float)0.7; - else if (iLBCdec_inst->consPLICount* - iLBCdec_inst->blockl>3*320) - use_gain=(float)0.5; - else if (iLBCdec_inst->consPLICount* - iLBCdec_inst->blockl>4*320) - use_gain=(float)0.0; - - /* mix noise and pitch repeatition */ - ftmp=(float)sqrt(max_per); - if (ftmp>(float)0.7) - pitchfact=(float)1.0; - else if (ftmp>(float)0.4) - pitchfact=(ftmp-(float)0.4)/((float)0.7-(float)0.4); - else - pitchfact=0.0; - - - /* avoid repetition of same pitch cycle */ - use_lag=lag; - if (lag<80) { - use_lag=2*lag; - } - - /* compute concealed residual */ - - - - -Andersen, et al. Experimental [Page 107] - -RFC 3951 Internet Low Bit Rate Codec December 2004 - - - energy = 0.0; - for (i=0; iblockl; i++) { - - /* noise component */ - - iLBCdec_inst->seed=(iLBCdec_inst->seed*69069L+1) & - (0x80000000L-1); - randlag = 50 + ((signed long) iLBCdec_inst->seed)%70; - pick = i - randlag; - - if (pick < 0) { - randvec[i] = - iLBCdec_inst->prevResidual[ - iLBCdec_inst->blockl+pick]; - } else { - randvec[i] = randvec[pick]; - } - - /* pitch repeatition component */ - pick = i - use_lag; - - if (pick < 0) { - PLCresidual[i] = - iLBCdec_inst->prevResidual[ - iLBCdec_inst->blockl+pick]; - } else { - PLCresidual[i] = PLCresidual[pick]; - } - - /* mix random and periodicity component */ - - if (i<80) - PLCresidual[i] = use_gain*(pitchfact * - PLCresidual[i] + - ((float)1.0 - pitchfact) * randvec[i]); - else if (i<160) - PLCresidual[i] = (float)0.95*use_gain*(pitchfact * - PLCresidual[i] + - ((float)1.0 - pitchfact) * randvec[i]); - else - PLCresidual[i] = (float)0.9*use_gain*(pitchfact * - PLCresidual[i] + - ((float)1.0 - pitchfact) * randvec[i]); - - energy += PLCresidual[i] * PLCresidual[i]; - } - - /* less than 30 dB, use only noise */ - - - -Andersen, et al. Experimental [Page 108] - -RFC 3951 Internet Low Bit Rate Codec December 2004 - - - - if (sqrt(energy/(float)iLBCdec_inst->blockl) < 30.0) { - gain=0.0; - for (i=0; iblockl; i++) { - PLCresidual[i] = randvec[i]; - } - } - - /* use old LPC */ - - memcpy(PLClpc,iLBCdec_inst->prevLpc, - (LPC_FILTERORDER+1)*sizeof(float)); - - } - - /* no packet loss, copy input */ - - else { - memcpy(PLCresidual, decresidual, - iLBCdec_inst->blockl*sizeof(float)); - memcpy(PLClpc, lpc, (LPC_FILTERORDER+1)*sizeof(float)); - iLBCdec_inst->consPLICount = 0; - } - - /* update state */ - - if (PLI) { - iLBCdec_inst->prevLag = lag; - iLBCdec_inst->per=max_per; - } - - iLBCdec_inst->prevPLI = PLI; - memcpy(iLBCdec_inst->prevLpc, PLClpc, - (LPC_FILTERORDER+1)*sizeof(float)); - memcpy(iLBCdec_inst->prevResidual, PLCresidual, - iLBCdec_inst->blockl*sizeof(float)); - } - -A.15. enhancer.h - - /****************************************************************** - - iLBC Speech Coder ANSI-C Source Code - - enhancer.h - - Copyright (C) The Internet Society (2004). - All Rights Reserved. - - - -Andersen, et al. Experimental [Page 109] - -RFC 3951 Internet Low Bit Rate Codec December 2004 - - - ******************************************************************/ - - #ifndef __ENHANCER_H - #define __ENHANCER_H - - #include "iLBC_define.h" - - float xCorrCoef( - float *target, /* (i) first array */ - float *regressor, /* (i) second array */ - int subl /* (i) dimension arrays */ - ); - - int enhancerInterface( - float *out, /* (o) the enhanced recidual signal */ - float *in, /* (i) the recidual signal to enhance */ - iLBC_Dec_Inst_t *iLBCdec_inst - /* (i/o) the decoder state structure */ - ); - - #endif - -A.16. enhancer.c - - /****************************************************************** - - iLBC Speech Coder ANSI-C Source Code - - enhancer.c - - Copyright (C) The Internet Society (2004). - All Rights Reserved. - - ******************************************************************/ - - #include - #include - #include "iLBC_define.h" - #include "constants.h" - #include "filter.h" - - /*----------------------------------------------------------------* - * Find index in array such that the array element with said - * index is the element of said array closest to "value" - * according to the squared-error criterion - *---------------------------------------------------------------*/ - - void NearestNeighbor( - - - -Andersen, et al. Experimental [Page 110] - -RFC 3951 Internet Low Bit Rate Codec December 2004 - - - int *index, /* (o) index of array element closest - to value */ - float *array, /* (i) data array */ - float value,/* (i) value */ - int arlength/* (i) dimension of data array */ - ){ - int i; - float bestcrit,crit; - - crit=array[0]-value; - bestcrit=crit*crit; - *index=0; - for (i=1; i dim1 ) { - hfl2=(int) (dim1/2); - for (j=0; j= idatal) { - searchSegEndPos=idatal-ENH_BLOCKL-1; - } - corrdim=searchSegEndPos-searchSegStartPos+1; - - /* compute upsampled correlation (corr33) and find - location of max */ - - mycorr1(corrVec,idata+searchSegStartPos, - corrdim+ENH_BLOCKL-1,idata+centerStartPos,ENH_BLOCKL); - enh_upsample(corrVecUps,corrVec,corrdim,ENH_FL0); - tloc=0; maxv=corrVecUps[0]; - for (i=1; imaxv) { - tloc=i; - maxv=corrVecUps[i]; - } - } - - /* make vector can be upsampled without ever running outside - bounds */ - - *updStartPos= (float)searchSegStartPos + - (float)tloc/(float)ENH_UPS0+(float)1.0; - tloc2=(int)(tloc/ENH_UPS0); - - if (tloc>tloc2*ENH_UPS0) { - tloc2++; - } - st=searchSegStartPos+tloc2-ENH_FL0; - - if (st<0) { - memset(vect,0,-st*sizeof(float)); - memcpy(&vect[-st],idata, (ENH_VECTL+st)*sizeof(float)); - } - else { - - - -Andersen, et al. Experimental [Page 114] - -RFC 3951 Internet Low Bit Rate Codec December 2004 - - - en=st+ENH_VECTL; - - if (en>idatal) { - memcpy(vect, &idata[st], - (ENH_VECTL-(en-idatal))*sizeof(float)); - memset(&vect[ENH_VECTL-(en-idatal)], 0, - (en-idatal)*sizeof(float)); - } - else { - memcpy(vect, &idata[st], ENH_VECTL*sizeof(float)); - } - } - fraction=tloc2*ENH_UPS0-tloc; - - /* compute the segment (this is actually a convolution) */ - - mycorr1(seg,vect,ENH_VECTL,polyphaserTbl+(2*ENH_FL0+1)*fraction, - 2*ENH_FL0+1); - } - - /*----------------------------------------------------------------* - * find the smoothed output data - *---------------------------------------------------------------*/ - - void smath( - float *odata, /* (o) smoothed output */ - float *sseq,/* (i) said second sequence of waveforms */ - int hl, /* (i) 2*hl+1 is sseq dimension */ - float alpha0/* (i) max smoothing energy fraction */ - ){ - int i,k; - float w00,w10,w11,A,B,C,*psseq,err,errs; - float surround[BLOCKL_MAX]; /* shape contributed by other than - current */ - float wt[2*ENH_HL+1]; /* waveform weighting to get - surround shape */ - float denom; - - /* create shape of contribution from all waveforms except the - current one */ - - for (i=1; i<=2*hl+1; i++) { - wt[i-1] = (float)0.5*(1 - (float)cos(2*PI*i/(2*hl+2))); - } - wt[hl]=0.0; /* for clarity, not used */ - for (i=0; i alpha0 * w00) { - if ( w00 < 1) { - w00=1; - } - denom = (w11*w00-w10*w10)/(w00*w00); - - if (denom > 0.0001) { /* eliminates numerical problems - for if smooth */ - - - -Andersen, et al. Experimental [Page 116] - -RFC 3951 Internet Low Bit Rate Codec December 2004 - - - A = (float)sqrt( (alpha0- alpha0*alpha0/4)/denom); - B = -alpha0/2 - A * w10/w00; - B = B+1; - } - else { /* essentially no difference between cycles; - smoothing not needed */ - A= 0.0; - B= 1.0; - } - - /* create smoothed sequence */ - - psseq=sseq+hl*ENH_BLOCKL; - for (i=0; i=0; q--) { - blockStartPos[q]=blockStartPos[q+1]-period[lagBlock[q+1]]; - NearestNeighbor(lagBlock+q,plocs, - blockStartPos[q]+ - ENH_BLOCKL_HALF-period[lagBlock[q+1]], periodl); - - - if (blockStartPos[q]-ENH_OVERHANG>=0) { - refiner(sseq+q*ENH_BLOCKL, blockStartPos+q, idata, - idatal, centerStartPos, blockStartPos[q], - period[lagBlock[q+1]]); - } else { - psseq=sseq+q*ENH_BLOCKL; - memset(psseq, 0, ENH_BLOCKL*sizeof(float)); - } - } - - /* future */ - - for (i=0; i 0.0) { - return (float)(ftmp1*ftmp1/ftmp2); - } - - - -Andersen, et al. Experimental [Page 119] - -RFC 3951 Internet Low Bit Rate Codec December 2004 - - - else { - return (float)0.0; - } - } - - /*----------------------------------------------------------------* - * interface for enhancer - *---------------------------------------------------------------*/ - - int enhancerInterface( - float *out, /* (o) enhanced signal */ - float *in, /* (i) unenhanced signal */ - iLBC_Dec_Inst_t *iLBCdec_inst /* (i) buffers etc */ - ){ - float *enh_buf, *enh_period; - int iblock, isample; - int lag=0, ilag, i, ioffset; - float cc, maxcc; - float ftmp1, ftmp2; - float *inPtr, *enh_bufPtr1, *enh_bufPtr2; - float plc_pred[ENH_BLOCKL]; - - float lpState[6], downsampled[(ENH_NBLOCKS*ENH_BLOCKL+120)/2]; - int inLen=ENH_NBLOCKS*ENH_BLOCKL+120; - int start, plc_blockl, inlag; - - enh_buf=iLBCdec_inst->enh_buf; - enh_period=iLBCdec_inst->enh_period; - - memmove(enh_buf, &enh_buf[iLBCdec_inst->blockl], - (ENH_BUFL-iLBCdec_inst->blockl)*sizeof(float)); - - memcpy(&enh_buf[ENH_BUFL-iLBCdec_inst->blockl], in, - iLBCdec_inst->blockl*sizeof(float)); - - if (iLBCdec_inst->mode==30) - plc_blockl=ENH_BLOCKL; - else - plc_blockl=40; - - /* when 20 ms frame, move processing one block */ - ioffset=0; - if (iLBCdec_inst->mode==20) ioffset=1; - - i=3-ioffset; - memmove(enh_period, &enh_period[i], - (ENH_NBLOCKS_TOT-i)*sizeof(float)); - - - - -Andersen, et al. Experimental [Page 120] - -RFC 3951 Internet Low Bit Rate Codec December 2004 - - - /* Set state information to the 6 samples right before - the samples to be downsampled. */ - - memcpy(lpState, - enh_buf+(ENH_NBLOCKS_EXTRA+ioffset)*ENH_BLOCKL-126, - 6*sizeof(float)); - - /* Down sample a factor 2 to save computations */ - - DownSample(enh_buf+(ENH_NBLOCKS_EXTRA+ioffset)*ENH_BLOCKL-120, - lpFilt_coefsTbl, inLen-ioffset*ENH_BLOCKL, - lpState, downsampled); - - /* Estimate the pitch in the down sampled domain. */ - for (iblock = 0; iblock maxcc) { - maxcc = cc; - lag = ilag; - } - } - - /* Store the estimated lag in the non-downsampled domain */ - enh_period[iblock+ENH_NBLOCKS_EXTRA+ioffset] = (float)lag*2; - - - } - - - /* PLC was performed on the previous packet */ - if (iLBCdec_inst->prev_enh_pl==1) { - - inlag=(int)enh_period[ENH_NBLOCKS_EXTRA+ioffset]; - - lag = inlag-1; - maxcc = xCorrCoef(in, in+lag, plc_blockl); - for (ilag=inlag; ilag<=inlag+1; ilag++) { - cc = xCorrCoef(in, in+ilag, plc_blockl); - - - - -Andersen, et al. Experimental [Page 121] - -RFC 3951 Internet Low Bit Rate Codec December 2004 - - - if (cc > maxcc) { - maxcc = cc; - lag = ilag; - } - } - - enh_period[ENH_NBLOCKS_EXTRA+ioffset-1]=(float)lag; - - /* compute new concealed residual for the old lookahead, - mix the forward PLC with a backward PLC from - the new frame */ - - inPtr=&in[lag-1]; - - enh_bufPtr1=&plc_pred[plc_blockl-1]; - - if (lag>plc_blockl) { - start=plc_blockl; - } else { - start=lag; - } - - for (isample = start; isample>0; isample--) { - *enh_bufPtr1-- = *inPtr--; - } - - enh_bufPtr2=&enh_buf[ENH_BUFL-1-iLBCdec_inst->blockl]; - for (isample = (plc_blockl-1-lag); isample>=0; isample--) { - *enh_bufPtr1-- = *enh_bufPtr2--; - } - - /* limit energy change */ - ftmp2=0.0; - ftmp1=0.0; - for (i=0;iblockl-i]* - enh_buf[ENH_BUFL-1-iLBCdec_inst->blockl-i]; - ftmp1+=plc_pred[i]*plc_pred[i]; - } - ftmp1=(float)sqrt(ftmp1/(float)plc_blockl); - ftmp2=(float)sqrt(ftmp2/(float)plc_blockl); - if (ftmp1>(float)2.0*ftmp2 && ftmp1>0.0) { - for (i=0;iblockl]; - for (i=0; imode==20) { - /* Enhancer with 40 samples delay */ - for (iblock = 0; iblock<2; iblock++) { - enhancer(out+iblock*ENH_BLOCKL, enh_buf, - ENH_BUFL, (5+iblock)*ENH_BLOCKL+40, - ENH_ALPHA0, enh_period, enh_plocsTbl, - ENH_NBLOCKS_TOT); - } - } else if (iLBCdec_inst->mode==30) { - /* Enhancer with 80 samples delay */ - for (iblock = 0; iblock<3; iblock++) { - enhancer(out+iblock*ENH_BLOCKL, enh_buf, - ENH_BUFL, (4+iblock)*ENH_BLOCKL, - ENH_ALPHA0, enh_period, enh_plocsTbl, - ENH_NBLOCKS_TOT); - } - } - - return (lag*2); - } - -A.17. filter.h - - /****************************************************************** - - iLBC Speech Coder ANSI-C Source Code - - filter.h - - Copyright (C) The Internet Society (2004). - All Rights Reserved. - - ******************************************************************/ - - - - -Andersen, et al. Experimental [Page 123] - -RFC 3951 Internet Low Bit Rate Codec December 2004 - - - #ifndef __iLBC_FILTER_H - #define __iLBC_FILTER_H - - void AllPoleFilter( - float *InOut, /* (i/o) on entrance InOut[-orderCoef] to - InOut[-1] contain the state of the - filter (delayed samples). InOut[0] to - InOut[lengthInOut-1] contain the filter - input, on en exit InOut[-orderCoef] to - InOut[-1] is unchanged and InOut[0] to - InOut[lengthInOut-1] contain filtered - samples */ - float *Coef,/* (i) filter coefficients, Coef[0] is assumed - to be 1.0 */ - int lengthInOut,/* (i) number of input/output samples */ - int orderCoef /* (i) number of filter coefficients */ - ); - - void AllZeroFilter( - float *In, /* (i) In[0] to In[lengthInOut-1] contain - filter input samples */ - float *Coef,/* (i) filter coefficients (Coef[0] is assumed - to be 1.0) */ - int lengthInOut,/* (i) number of input/output samples */ - int orderCoef, /* (i) number of filter coefficients */ - float *Out /* (i/o) on entrance Out[-orderCoef] to Out[-1] - contain the filter state, on exit Out[0] - to Out[lengthInOut-1] contain filtered - samples */ - ); - - void ZeroPoleFilter( - float *In, /* (i) In[0] to In[lengthInOut-1] contain filter - input samples In[-orderCoef] to In[-1] - contain state of all-zero section */ - float *ZeroCoef,/* (i) filter coefficients for all-zero - section (ZeroCoef[0] is assumed to - be 1.0) */ - float *PoleCoef,/* (i) filter coefficients for all-pole section - (ZeroCoef[0] is assumed to be 1.0) */ - int lengthInOut,/* (i) number of input/output samples */ - int orderCoef, /* (i) number of filter coefficients */ - float *Out /* (i/o) on entrance Out[-orderCoef] to Out[-1] - contain state of all-pole section. On - exit Out[0] to Out[lengthInOut-1] - contain filtered samples */ - ); - - - - -Andersen, et al. Experimental [Page 124] - -RFC 3951 Internet Low Bit Rate Codec December 2004 - - - void DownSample ( - float *In, /* (i) input samples */ - float *Coef, /* (i) filter coefficients */ - int lengthIn, /* (i) number of input samples */ - float *state, /* (i) filter state */ - float *Out /* (o) downsampled output */ - ); - - #endif - -A.18. filter.c - - /****************************************************************** - - iLBC Speech Coder ANSI-C Source Code - - filter.c - - Copyright (C) The Internet Society (2004). - All Rights Reserved. - - ******************************************************************/ - - #include "iLBC_define.h" - - /*----------------------------------------------------------------* - * all-pole filter - *---------------------------------------------------------------*/ - - void AllPoleFilter( - float *InOut, /* (i/o) on entrance InOut[-orderCoef] to - InOut[-1] contain the state of the - filter (delayed samples). InOut[0] to - InOut[lengthInOut-1] contain the filter - input, on en exit InOut[-orderCoef] to - InOut[-1] is unchanged and InOut[0] to - InOut[lengthInOut-1] contain filtered - samples */ - float *Coef,/* (i) filter coefficients, Coef[0] is assumed - to be 1.0 */ - int lengthInOut,/* (i) number of input/output samples */ - int orderCoef /* (i) number of filter coefficients */ - ){ - int n,k; - - for(n=0;nnsub-1; n++) { - pp=residual+n*SUBL; - for (l=0; l<5; l++) { - fssqEn[n] += sampEn_win[l] * (*pp) * (*pp); - bssqEn[n] += (*pp) * (*pp); - pp++; - } - for (l=5; lnsub-1; - pp=residual+n*SUBL; - for (l=0; lmode==20) l=1; - else l=0; - - max_ssqEn=(fssqEn[0]+bssqEn[1])*ssqEn_win[l]; - max_ssqEn_n=1; - for (n=2; nnsub; n++) { - - - - -Andersen, et al. Experimental [Page 130] - -RFC 3951 Internet Low Bit Rate Codec December 2004 - - - l++; - if ((fssqEn[n-1]+bssqEn[n])*ssqEn_win[l] > max_ssqEn) { - max_ssqEn=(fssqEn[n-1]+bssqEn[n]) * - ssqEn_win[l]; - max_ssqEn_n=n; - } - } - - return max_ssqEn_n; - } - -A.21. gainquant.h - - /****************************************************************** - - iLBC Speech Coder ANSI-C Source Code - - gainquant.h - - Copyright (C) The Internet Society (2004). - All Rights Reserved. - - ******************************************************************/ - - #ifndef __iLBC_GAINQUANT_H - #define __iLBC_GAINQUANT_H - - float gainquant(/* (o) quantized gain value */ - float in, /* (i) gain value */ - float maxIn,/* (i) maximum of gain value */ - int cblen, /* (i) number of quantization indices */ - int *index /* (o) quantization index */ - ); - - float gaindequant( /* (o) quantized gain value */ - int index, /* (i) quantization index */ - float maxIn,/* (i) maximum of unquantized gain */ - int cblen /* (i) number of quantization indices */ - ); - - #endif - -A.22. gainquant.c - - /****************************************************************** - - iLBC Speech Coder ANSI-C Source Code - - - - -Andersen, et al. Experimental [Page 131] - -RFC 3951 Internet Low Bit Rate Codec December 2004 - - - gainquant.c - - Copyright (C) The Internet Society (2004). - All Rights Reserved. - - ******************************************************************/ - - #include - #include - #include "constants.h" - #include "filter.h" - - /*----------------------------------------------------------------* - * quantizer for the gain in the gain-shape coding of residual - *---------------------------------------------------------------*/ - - float gainquant(/* (o) quantized gain value */ - float in, /* (i) gain value */ - float maxIn,/* (i) maximum of gain value */ - int cblen, /* (i) number of quantization indices */ - int *index /* (o) quantization index */ - ){ - int i, tindex; - float minmeasure,measure, *cb, scale; - - /* ensure a lower bound on the scaling factor */ - - scale=maxIn; - - if (scale<0.1) { - scale=(float)0.1; - } - - /* select the quantization table */ - - if (cblen == 8) { - cb = gain_sq3Tbl; - } else if (cblen == 16) { - cb = gain_sq4Tbl; - } else { - cb = gain_sq5Tbl; - } - - /* select the best index in the quantization table */ - - minmeasure=10000000.0; - tindex=0; - for (i=0; i - - /*----------------------------------------------------------------* - * Construct codebook vector for given index. - *---------------------------------------------------------------*/ - - void getCBvec( - - - -Andersen, et al. Experimental [Page 134] - -RFC 3951 Internet Low Bit Rate Codec December 2004 - - - float *cbvec, /* (o) Constructed codebook vector */ - float *mem, /* (i) Codebook buffer */ - int index, /* (i) Codebook index */ - int lMem, /* (i) Length of codebook buffer */ - int cbveclen/* (i) Codebook vector length */ - ){ - int j, k, n, memInd, sFilt; - float tmpbuf[CB_MEML]; - int base_size; - int ilow, ihigh; - float alfa, alfa1; - - /* Determine size of codebook sections */ - - base_size=lMem-cbveclen+1; - - if (cbveclen==SUBL) { - base_size+=cbveclen/2; - } - - /* No filter -> First codebook section */ - - if (index - - #include "iLBC_define.h" - #include "constants.h" - - /*----------------------------------------------------------------* - * calculation of auto correlation - *---------------------------------------------------------------*/ - - void autocorr( - float *r, /* (o) autocorrelation vector */ - const float *x, /* (i) data vector */ - int N, /* (i) length of data vector */ - int order /* largest lag for calculated - autocorrelations */ - ){ - int lag, n; - float sum; - - for (lag = 0; lag <= order; lag++) { - sum = 0; - for (n = 0; n < N - lag; n++) { - sum += x[n] * x[n+lag]; - } - r[lag] = sum; - } - - - -Andersen, et al. Experimental [Page 140] - -RFC 3951 Internet Low Bit Rate Codec December 2004 - - - } - - /*----------------------------------------------------------------* - * window multiplication - *---------------------------------------------------------------*/ - - void window( - float *z, /* (o) the windowed data */ - const float *x, /* (i) the original data vector */ - const float *y, /* (i) the window */ - int N /* (i) length of all vectors */ - ){ - int i; - - for (i = 0; i < N; i++) { - z[i] = x[i] * y[i]; - } - } - - /*----------------------------------------------------------------* - * levinson-durbin solution for lpc coefficients - *---------------------------------------------------------------*/ - - void levdurb( - float *a, /* (o) lpc coefficient vector starting - with 1.0 */ - float *k, /* (o) reflection coefficients */ - float *r, /* (i) autocorrelation vector */ - int order /* (i) order of lpc filter */ - ){ - float sum, alpha; - int m, m_h, i; - - a[0] = 1.0; - - if (r[0] < EPS) { /* if r[0] <= 0, set LPC coeff. to zero */ - for (i = 0; i < order; i++) { - k[i] = 0; - a[i+1] = 0; - } - } else { - a[1] = k[0] = -r[1]/r[0]; - alpha = r[0] + r[1] * k[0]; - for (m = 1; m < order; m++){ - sum = r[m + 1]; - for (i = 0; i < m; i++){ - sum += a[i+1] * r[m - i]; - } - - - -Andersen, et al. Experimental [Page 141] - -RFC 3951 Internet Low Bit Rate Codec December 2004 - - - k[m] = -sum / alpha; - alpha += k[m] * sum; - m_h = (m + 1) >> 1; - for (i = 0; i < m_h; i++){ - sum = a[i+1] + k[m] * a[m - i]; - a[m - i] += k[m] * a[i+1]; - a[i+1] = sum; - } - a[m+1] = k[m]; - } - } - } - - /*----------------------------------------------------------------* - * interpolation between vectors - *---------------------------------------------------------------*/ - - void interpolate( - float *out, /* (o) the interpolated vector */ - float *in1, /* (i) the first vector for the - interpolation */ - float *in2, /* (i) the second vector for the - interpolation */ - float coef, /* (i) interpolation weights */ - int length /* (i) length of all vectors */ - ){ - int i; - float invcoef; - - invcoef = (float)1.0 - coef; - for (i = 0; i < length; i++) { - out[i] = coef * in1[i] + invcoef * in2[i]; - } - } - - /*----------------------------------------------------------------* - * lpc bandwidth expansion - *---------------------------------------------------------------*/ - - void bwexpand( - float *out, /* (o) the bandwidth expanded lpc - coefficients */ - float *in, /* (i) the lpc coefficients before bandwidth - expansion */ - float coef, /* (i) the bandwidth expansion factor */ - int length /* (i) the length of lpc coefficient vectors */ - ){ - int i; - - - -Andersen, et al. Experimental [Page 142] - -RFC 3951 Internet Low Bit Rate Codec December 2004 - - - float chirp; - - chirp = coef; - - out[0] = in[0]; - for (i = 1; i < length; i++) { - out[i] = chirp * in[i]; - chirp *= coef; - } - } - - /*----------------------------------------------------------------* - * vector quantization - *---------------------------------------------------------------*/ - - void vq( - float *Xq, /* (o) the quantized vector */ - int *index, /* (o) the quantization index */ - const float *CB,/* (i) the vector quantization codebook */ - float *X, /* (i) the vector to quantize */ - int n_cb, /* (i) the number of vectors in the codebook */ - int dim /* (i) the dimension of all vectors */ - ){ - int i, j; - int pos, minindex; - float dist, tmp, mindist; - - pos = 0; - mindist = FLOAT_MAX; - minindex = 0; - for (j = 0; j < n_cb; j++) { - dist = X[0] - CB[pos]; - dist *= dist; - for (i = 1; i < dim; i++) { - tmp = X[i] - CB[pos + i]; - dist += tmp*tmp; - } - - if (dist < mindist) { - mindist = dist; - minindex = j; - } - pos += dim; - } - for (i = 0; i < dim; i++) { - Xq[i] = CB[minindex*dim + i]; - } - *index = minindex; - - - -Andersen, et al. Experimental [Page 143] - -RFC 3951 Internet Low Bit Rate Codec December 2004 - - - } - - /*----------------------------------------------------------------* - * split vector quantization - *---------------------------------------------------------------*/ - - void SplitVQ( - float *qX, /* (o) the quantized vector */ - int *index, /* (o) a vector of indexes for all vector - codebooks in the split */ - float *X, /* (i) the vector to quantize */ - const float *CB,/* (i) the quantizer codebook */ - int nsplit, /* the number of vector splits */ - const int *dim, /* the dimension of X and qX */ - const int *cbsize /* the number of vectors in the codebook */ - ){ - int cb_pos, X_pos, i; - - cb_pos = 0; - X_pos= 0; - for (i = 0; i < nsplit; i++) { - vq(qX + X_pos, index + i, CB + cb_pos, X + X_pos, - cbsize[i], dim[i]); - X_pos += dim[i]; - cb_pos += dim[i] * cbsize[i]; - } - } - - /*----------------------------------------------------------------* - * scalar quantization - *---------------------------------------------------------------*/ - - void sort_sq( - float *xq, /* (o) the quantized value */ - int *index, /* (o) the quantization index */ - float x, /* (i) the value to quantize */ - const float *cb,/* (i) the quantization codebook */ - int cb_size /* (i) the size of the quantization codebook */ - ){ - int i; - - if (x <= cb[0]) { - *index = 0; - *xq = cb[0]; - } else { - i = 0; - while ((x > cb[i]) && i < cb_size - 1) { - i++; - - - -Andersen, et al. Experimental [Page 144] - -RFC 3951 Internet Low Bit Rate Codec December 2004 - - - } - - if (x > ((cb[i] + cb[i - 1])/2)) { - *index = i; - *xq = cb[i]; - } else { - *index = i - 1; - *xq = cb[i - 1]; - } - } - } - - /*----------------------------------------------------------------* - * check for stability of lsf coefficients - *---------------------------------------------------------------*/ - - int LSF_check( /* (o) 1 for stable lsf vectors and 0 for - nonstable ones */ - float *lsf, /* (i) a table of lsf vectors */ - int dim, /* (i) the dimension of each lsf vector */ - int NoAn /* (i) the number of lsf vectors in the - table */ - ){ - int k,n,m, Nit=2, change=0,pos; - float tmp; - static float eps=(float)0.039; /* 50 Hz */ - static float eps2=(float)0.0195; - static float maxlsf=(float)3.14; /* 4000 Hz */ - static float minlsf=(float)0.01; /* 0 Hz */ - - /* LSF separation check*/ - - for (n=0; nmaxlsf) { - lsf[pos]=maxlsf; - change=1; - } - } - } - } - - return change; - } - -A.27. hpInput.h - - /****************************************************************** - - iLBC Speech Coder ANSI-C Source Code - - hpInput.h - - Copyright (C) The Internet Society (2004). - All Rights Reserved. - - ******************************************************************/ - - #ifndef __iLBC_HPINPUT_H - #define __iLBC_HPINPUT_H - - void hpInput( - float *In, /* (i) vector to filter */ - int len, /* (i) length of vector to filter */ - float *Out, /* (o) the resulting filtered vector */ - float *mem /* (i/o) the filter state */ - ); - - #endif - -A.28. hpInput.c - - /****************************************************************** - - iLBC Speech Coder ANSI-C Source Code - - - -Andersen, et al. Experimental [Page 146] - -RFC 3951 Internet Low Bit Rate Codec December 2004 - - - hpInput.c - - Copyright (C) The Internet Society (2004). - All Rights Reserved. - - ******************************************************************/ - - #include "constants.h" - - /*----------------------------------------------------------------* - * Input high-pass filter - *---------------------------------------------------------------*/ - - void hpInput( - float *In, /* (i) vector to filter */ - int len, /* (i) length of vector to filter */ - float *Out, /* (o) the resulting filtered vector */ - float *mem /* (i/o) the filter state */ - ){ - int i; - float *pi, *po; - - /* all-zero section*/ - - pi = &In[0]; - po = &Out[0]; - for (i=0; i - - #include "iLBC_define.h" - #include "gainquant.h" - #include "getCBvec.h" - - /*----------------------------------------------------------------* - * Convert the codebook indexes to make the search easier - *---------------------------------------------------------------*/ - - - - -Andersen, et al. Experimental [Page 150] - -RFC 3951 Internet Low Bit Rate Codec December 2004 - - - void index_conv_enc( - int *index /* (i/o) Codebook indexes */ - ){ - int k; - - for (k=1; k=108)&&(index[k]<172)) { - index[k]-=64; - } else if (index[k]>=236) { - index[k]-=128; - } else { - /* ERROR */ - } - } - } - - void index_conv_dec( - int *index /* (i/o) Codebook indexes */ - ){ - int k; - - for (k=1; k=44)&&(index[k]<108)) { - index[k]+=64; - } else if ((index[k]>=108)&&(index[k]<128)) { - index[k]+=128; - } else { - /* ERROR */ - } - } - } - - /*----------------------------------------------------------------* - * Construct decoded vector from codebook and gains. - *---------------------------------------------------------------*/ - - void iCBConstruct( - float *decvector, /* (o) Decoded vector */ - int *index, /* (i) Codebook indices */ - int *gain_index,/* (i) Gain quantization indices */ - float *mem, /* (i) Buffer for codevector construction */ - int lMem, /* (i) Length of buffer */ - int veclen, /* (i) Length of vector */ - int nStages /* (i) Number of codebook stages */ - ){ - int j,k; - - - -Andersen, et al. Experimental [Page 151] - -RFC 3951 Internet Low Bit Rate Codec December 2004 - - - float gain[CB_NSTAGES]; - float cbvec[SUBL]; - - /* gain de-quantization */ - - gain[0] = gaindequant(gain_index[0], 1.0, 32); - if (nStages > 1) { - gain[1] = gaindequant(gain_index[1], - (float)fabs(gain[0]), 16); - } - if (nStages > 2) { - gain[2] = gaindequant(gain_index[2], - (float)fabs(gain[1]), 8); - } - - /* codebook vector construction and construction of - total vector */ - - getCBvec(cbvec, mem, index[0], lMem, veclen); - for (j=0;j 1) { - for (k=1; k - #include - - #include "iLBC_define.h" - #include "gainquant.h" - #include "createCB.h" - #include "filter.h" - #include "constants.h" - - /*----------------------------------------------------------------* - * Search routine for codebook encoding and gain quantization. - *---------------------------------------------------------------*/ - - void iCBSearch( - iLBC_Enc_Inst_t *iLBCenc_inst, - /* (i) the encoder state structure */ - int *index, /* (o) Codebook indices */ - int *gain_index,/* (o) Gain quantization indices */ - - - -Andersen, et al. Experimental [Page 153] - -RFC 3951 Internet Low Bit Rate Codec December 2004 - - - float *intarget,/* (i) Target vector for encoding */ - float *mem, /* (i) Buffer for codebook construction */ - int lMem, /* (i) Length of buffer */ - int lTarget, /* (i) Length of vector */ - int nStages, /* (i) Number of codebook stages */ - float *weightDenum, /* (i) weighting filter coefficients */ - float *weightState, /* (i) weighting filter state */ - int block /* (i) the sub-block number */ - ){ - int i, j, icount, stage, best_index, range, counter; - float max_measure, gain, measure, crossDot, ftmp; - float gains[CB_NSTAGES]; - float target[SUBL]; - int base_index, sInd, eInd, base_size; - int sIndAug=0, eIndAug=0; - float buf[CB_MEML+SUBL+2*LPC_FILTERORDER]; - float invenergy[CB_EXPAND*128], energy[CB_EXPAND*128]; - float *pp, *ppi=0, *ppo=0, *ppe=0; - float cbvectors[CB_MEML]; - float tene, cene, cvec[SUBL]; - float aug_vec[SUBL]; - - memset(cvec,0,SUBL*sizeof(float)); - - /* Determine size of codebook sections */ - - base_size=lMem-lTarget+1; - - if (lTarget==SUBL) { - base_size=lMem-lTarget+1+lTarget/2; - } - - /* setup buffer for weighting */ - - memcpy(buf,weightState,sizeof(float)*LPC_FILTERORDER); - memcpy(buf+LPC_FILTERORDER,mem,lMem*sizeof(float)); - memcpy(buf+LPC_FILTERORDER+lMem,intarget,lTarget*sizeof(float)); - - /* weighting */ - - AllPoleFilter(buf+LPC_FILTERORDER, weightDenum, - lMem+lTarget, LPC_FILTERORDER); - - /* Construct the codebook and target needed */ - - memcpy(target, buf+LPC_FILTERORDER+lMem, lTarget*sizeof(float)); - - tene=0.0; - - - -Andersen, et al. Experimental [Page 154] - -RFC 3951 Internet Low Bit Rate Codec December 2004 - - - for (i=0; i0.0) { - invenergy[0] = (float) 1.0 / (*ppe + EPS); - } else { - invenergy[0] = (float) 0.0; - - - -Andersen, et al. Experimental [Page 155] - -RFC 3951 Internet Low Bit Rate Codec December 2004 - - - } - ppe++; - - measure=(float)-10000000.0; - - if (crossDot > 0.0) { - measure = crossDot*crossDot*invenergy[0]; - } - } - else { - measure = crossDot*crossDot*invenergy[0]; - } - - /* check if measure is better */ - ftmp = crossDot*invenergy[0]; - - if ((measure>max_measure) && (fabs(ftmp)0.0) { - invenergy[icount] = - (float)1.0/(energy[icount]+EPS); - } else { - invenergy[icount] = (float) 0.0; - } - - - -Andersen, et al. Experimental [Page 156] - -RFC 3951 Internet Low Bit Rate Codec December 2004 - - - measure=(float)-10000000.0; - - if (crossDot > 0.0) { - measure = crossDot*crossDot*invenergy[icount]; - } - } - else { - measure = crossDot*crossDot*invenergy[icount]; - } - - /* check if measure is better */ - ftmp = crossDot*invenergy[icount]; - - if ((measure>max_measure) && (fabs(ftmp) range) { - sInd -= (eInd-range); - eInd = range; - } - } else { /* base_index >= (base_size-20) */ - - if (sInd < (base_size-20)) { - sIndAug = 20; - sInd = 0; - eInd = 0; - eIndAug = 19 + CB_RESRANGE; - - if(eIndAug > 39) { - eInd = eIndAug-39; - eIndAug = 39; - } - } else { - sIndAug = 20 + sInd - (base_size-20); - eIndAug = 39; - sInd = 0; - eInd = CB_RESRANGE - (eIndAug-sIndAug+1); - } - } - - } else { /* lTarget = 22 or 23 */ - - if (sInd < 0) { - eInd -= sInd; - - - -Andersen, et al. Experimental [Page 158] - -RFC 3951 Internet Low Bit Rate Codec December 2004 - - - sInd = 0; - } - - if(eInd > range) { - sInd -= (eInd - range); - eInd = range; - } - } - } - - /* search of higher codebook section */ - - /* index search range */ - counter = sInd; - sInd += base_size; - eInd += base_size; - - - if (stage==0) { - ppe = energy+base_size; - *ppe=0.0; - - pp=cbvectors+lMem-lTarget; - for (j=0; j0.0) { - invenergy[icount] =(float)1.0/(energy[icount]+EPS); - } else { - invenergy[icount] =(float)0.0; - } - - if (stage==0) { - - measure=(float)-10000000.0; - - if (crossDot > 0.0) { - measure = crossDot*crossDot* - invenergy[icount]; - } - } - else { - measure = crossDot*crossDot*invenergy[icount]; - } - - /* check if measure is better */ - ftmp = crossDot*invenergy[icount]; - - if ((measure>max_measure) && (fabs(ftmp)CB_MAXGAIN) { - gain = (float)CB_MAXGAIN; - } - gain = gainquant(gain, 1.0, 32, &gain_index[stage]); - } - else { - if (stage==1) { - gain = gainquant(gain, (float)fabs(gains[stage-1]), - 16, &gain_index[stage]); - } else { - gain = gainquant(gain, (float)fabs(gains[stage-1]), - 8, &gain_index[stage]); - } - } - - /* Extract the best (according to measure) - codebook vector */ - - if (lTarget==(STATE_LEN-iLBCenc_inst->state_short_len)) { - - if (index[stage] - #include - - #include "helpfun.h" - #include "lsf.h" - #include "iLBC_define.h" - #include "constants.h" - - /*---------------------------------------------------------------* - * interpolation of lsf coefficients for the decoder - *--------------------------------------------------------------*/ - - void LSFinterpolate2a_dec( - float *a, /* (o) lpc coefficients for a sub-frame */ - float *lsf1, /* (i) first lsf coefficient vector */ - float *lsf2, /* (i) second lsf coefficient vector */ - float coef, /* (i) interpolation weight */ - int length /* (i) length of lsf vectors */ - ){ - float lsftmp[LPC_FILTERORDER]; - - interpolate(lsftmp, lsf1, lsf2, coef, length); - lsf2a(a, lsftmp); - } - - /*---------------------------------------------------------------* - * obtain dequantized lsf coefficients from quantization index - *--------------------------------------------------------------*/ - - void SimplelsfDEQ( - float *lsfdeq, /* (o) dequantized lsf coefficients */ - int *index, /* (i) quantization index */ - int lpc_n /* (i) number of LPCs */ - ){ - int i, j, pos, cb_pos; - - - -Andersen, et al. Experimental [Page 164] - -RFC 3951 Internet Low Bit Rate Codec December 2004 - - - /* decode first LSF */ - - pos = 0; - cb_pos = 0; - for (i = 0; i < LSF_NSPLIT; i++) { - for (j = 0; j < dim_lsfCbTbl[i]; j++) { - lsfdeq[pos + j] = lsfCbTbl[cb_pos + - (long)(index[i])*dim_lsfCbTbl[i] + j]; - } - pos += dim_lsfCbTbl[i]; - cb_pos += size_lsfCbTbl[i]*dim_lsfCbTbl[i]; - } - - if (lpc_n>1) { - - /* decode last LSF */ - - pos = 0; - cb_pos = 0; - for (i = 0; i < LSF_NSPLIT; i++) { - for (j = 0; j < dim_lsfCbTbl[i]; j++) { - lsfdeq[LPC_FILTERORDER + pos + j] = - lsfCbTbl[cb_pos + - (long)(index[LSF_NSPLIT + i])* - dim_lsfCbTbl[i] + j]; - } - pos += dim_lsfCbTbl[i]; - cb_pos += size_lsfCbTbl[i]*dim_lsfCbTbl[i]; - } - } - } - - /*----------------------------------------------------------------* - * obtain synthesis and weighting filters form lsf coefficients - *---------------------------------------------------------------*/ - - void DecoderInterpolateLSF( - float *syntdenum, /* (o) synthesis filter coefficients */ - float *weightdenum, /* (o) weighting denumerator - coefficients */ - float *lsfdeq, /* (i) dequantized lsf coefficients */ - int length, /* (i) length of lsf coefficient vector */ - iLBC_Dec_Inst_t *iLBCdec_inst - /* (i) the decoder state structure */ - ){ - int i, pos, lp_length; - float lp[LPC_FILTERORDER + 1], *lsfdeq2; - - - - -Andersen, et al. Experimental [Page 165] - -RFC 3951 Internet Low Bit Rate Codec December 2004 - - - lsfdeq2 = lsfdeq + length; - lp_length = length + 1; - - if (iLBCdec_inst->mode==30) { - /* sub-frame 1: Interpolation between old and first */ - - LSFinterpolate2a_dec(lp, iLBCdec_inst->lsfdeqold, lsfdeq, - lsf_weightTbl_30ms[0], length); - memcpy(syntdenum,lp,lp_length*sizeof(float)); - bwexpand(weightdenum, lp, LPC_CHIRP_WEIGHTDENUM, - lp_length); - - /* sub-frames 2 to 6: interpolation between first - and last LSF */ - - pos = lp_length; - for (i = 1; i < 6; i++) { - LSFinterpolate2a_dec(lp, lsfdeq, lsfdeq2, - lsf_weightTbl_30ms[i], length); - memcpy(syntdenum + pos,lp,lp_length*sizeof(float)); - bwexpand(weightdenum + pos, lp, - LPC_CHIRP_WEIGHTDENUM, lp_length); - pos += lp_length; - } - } - else { - pos = 0; - for (i = 0; i < iLBCdec_inst->nsub; i++) { - LSFinterpolate2a_dec(lp, iLBCdec_inst->lsfdeqold, - lsfdeq, lsf_weightTbl_20ms[i], length); - memcpy(syntdenum+pos,lp,lp_length*sizeof(float)); - bwexpand(weightdenum+pos, lp, LPC_CHIRP_WEIGHTDENUM, - lp_length); - pos += lp_length; - } - } - - /* update memory */ - - if (iLBCdec_inst->mode==30) - memcpy(iLBCdec_inst->lsfdeqold, lsfdeq2, - length*sizeof(float)); - else - memcpy(iLBCdec_inst->lsfdeqold, lsfdeq, - length*sizeof(float)); - - } - - - - -Andersen, et al. Experimental [Page 166] - -RFC 3951 Internet Low Bit Rate Codec December 2004 - - -A.37. LPCencode.h - - /****************************************************************** - - iLBC Speech Coder ANSI-C Source Code - - LPCencode.h - - Copyright (C) The Internet Society (2004). - All Rights Reserved. - - ******************************************************************/ - - #ifndef __iLBC_LPCENCOD_H - #define __iLBC_LPCENCOD_H - - void LPCencode( - float *syntdenum, /* (i/o) synthesis filter coefficients - before/after encoding */ - float *weightdenum, /* (i/o) weighting denumerator coefficients - before/after encoding */ - int *lsf_index, /* (o) lsf quantization index */ - float *data, /* (i) lsf coefficients to quantize */ - iLBC_Enc_Inst_t *iLBCenc_inst - /* (i/o) the encoder state structure */ - ); - - #endif - -A.38. LPCencode.c - - /****************************************************************** - - iLBC Speech Coder ANSI-C Source Code - - LPCencode.c - - Copyright (C) The Internet Society (2004). - All Rights Reserved. - - ******************************************************************/ - - #include - - #include "iLBC_define.h" - #include "helpfun.h" - #include "lsf.h" - #include "constants.h" - - - -Andersen, et al. Experimental [Page 167] - -RFC 3951 Internet Low Bit Rate Codec December 2004 - - - /*----------------------------------------------------------------* - * lpc analysis (subrutine to LPCencode) - *---------------------------------------------------------------*/ - - void SimpleAnalysis( - float *lsf, /* (o) lsf coefficients */ - float *data, /* (i) new data vector */ - iLBC_Enc_Inst_t *iLBCenc_inst - /* (i/o) the encoder state structure */ - ){ - int k, is; - float temp[BLOCKL_MAX], lp[LPC_FILTERORDER + 1]; - float lp2[LPC_FILTERORDER + 1]; - float r[LPC_FILTERORDER + 1]; - - is=LPC_LOOKBACK+BLOCKL_MAX-iLBCenc_inst->blockl; - memcpy(iLBCenc_inst->lpc_buffer+is,data, - iLBCenc_inst->blockl*sizeof(float)); - - /* No lookahead, last window is asymmetric */ - - for (k = 0; k < iLBCenc_inst->lpc_n; k++) { - - is = LPC_LOOKBACK; - - if (k < (iLBCenc_inst->lpc_n - 1)) { - window(temp, lpc_winTbl, - iLBCenc_inst->lpc_buffer, BLOCKL_MAX); - } else { - window(temp, lpc_asymwinTbl, - iLBCenc_inst->lpc_buffer + is, BLOCKL_MAX); - } - - autocorr(r, temp, BLOCKL_MAX, LPC_FILTERORDER); - window(r, r, lpc_lagwinTbl, LPC_FILTERORDER + 1); - - levdurb(lp, temp, r, LPC_FILTERORDER); - bwexpand(lp2, lp, LPC_CHIRP_SYNTDENUM, LPC_FILTERORDER+1); - - a2lsf(lsf + k*LPC_FILTERORDER, lp2); - } - is=LPC_LOOKBACK+BLOCKL_MAX-iLBCenc_inst->blockl; - memmove(iLBCenc_inst->lpc_buffer, - iLBCenc_inst->lpc_buffer+LPC_LOOKBACK+BLOCKL_MAX-is, - is*sizeof(float)); - } - - /*----------------------------------------------------------------* - - - -Andersen, et al. Experimental [Page 168] - -RFC 3951 Internet Low Bit Rate Codec December 2004 - - - * lsf interpolator and conversion from lsf to a coefficients - * (subrutine to SimpleInterpolateLSF) - *---------------------------------------------------------------*/ - - void LSFinterpolate2a_enc( - float *a, /* (o) lpc coefficients */ - float *lsf1,/* (i) first set of lsf coefficients */ - float *lsf2,/* (i) second set of lsf coefficients */ - float coef, /* (i) weighting coefficient to use between - lsf1 and lsf2 */ - long length /* (i) length of coefficient vectors */ - ){ - float lsftmp[LPC_FILTERORDER]; - - interpolate(lsftmp, lsf1, lsf2, coef, length); - lsf2a(a, lsftmp); - } - - /*----------------------------------------------------------------* - * lsf interpolator (subrutine to LPCencode) - *---------------------------------------------------------------*/ - - void SimpleInterpolateLSF( - float *syntdenum, /* (o) the synthesis filter denominator - resulting from the quantized - interpolated lsf */ - float *weightdenum, /* (o) the weighting filter denominator - resulting from the unquantized - interpolated lsf */ - float *lsf, /* (i) the unquantized lsf coefficients */ - float *lsfdeq, /* (i) the dequantized lsf coefficients */ - float *lsfold, /* (i) the unquantized lsf coefficients of - the previous signal frame */ - float *lsfdeqold, /* (i) the dequantized lsf coefficients of - the previous signal frame */ - int length, /* (i) should equate LPC_FILTERORDER */ - iLBC_Enc_Inst_t *iLBCenc_inst - /* (i/o) the encoder state structure */ - ){ - int i, pos, lp_length; - float lp[LPC_FILTERORDER + 1], *lsf2, *lsfdeq2; - - lsf2 = lsf + length; - lsfdeq2 = lsfdeq + length; - lp_length = length + 1; - - if (iLBCenc_inst->mode==30) { - /* sub-frame 1: Interpolation between old and first - - - -Andersen, et al. Experimental [Page 169] - -RFC 3951 Internet Low Bit Rate Codec December 2004 - - - set of lsf coefficients */ - - LSFinterpolate2a_enc(lp, lsfdeqold, lsfdeq, - lsf_weightTbl_30ms[0], length); - memcpy(syntdenum,lp,lp_length*sizeof(float)); - LSFinterpolate2a_enc(lp, lsfold, lsf, - lsf_weightTbl_30ms[0], length); - bwexpand(weightdenum, lp, LPC_CHIRP_WEIGHTDENUM, lp_length); - - /* sub-frame 2 to 6: Interpolation between first - and second set of lsf coefficients */ - - pos = lp_length; - for (i = 1; i < iLBCenc_inst->nsub; i++) { - LSFinterpolate2a_enc(lp, lsfdeq, lsfdeq2, - lsf_weightTbl_30ms[i], length); - memcpy(syntdenum + pos,lp,lp_length*sizeof(float)); - - LSFinterpolate2a_enc(lp, lsf, lsf2, - lsf_weightTbl_30ms[i], length); - bwexpand(weightdenum + pos, lp, - LPC_CHIRP_WEIGHTDENUM, lp_length); - pos += lp_length; - } - } - else { - pos = 0; - for (i = 0; i < iLBCenc_inst->nsub; i++) { - LSFinterpolate2a_enc(lp, lsfdeqold, lsfdeq, - lsf_weightTbl_20ms[i], length); - memcpy(syntdenum+pos,lp,lp_length*sizeof(float)); - LSFinterpolate2a_enc(lp, lsfold, lsf, - lsf_weightTbl_20ms[i], length); - bwexpand(weightdenum+pos, lp, - LPC_CHIRP_WEIGHTDENUM, lp_length); - pos += lp_length; - } - } - - /* update memory */ - - if (iLBCenc_inst->mode==30) { - memcpy(lsfold, lsf2, length*sizeof(float)); - memcpy(lsfdeqold, lsfdeq2, length*sizeof(float)); - } - else { - memcpy(lsfold, lsf, length*sizeof(float)); - memcpy(lsfdeqold, lsfdeq, length*sizeof(float)); - - - -Andersen, et al. Experimental [Page 170] - -RFC 3951 Internet Low Bit Rate Codec December 2004 - - - } - } - - /*----------------------------------------------------------------* - * lsf quantizer (subrutine to LPCencode) - *---------------------------------------------------------------*/ - - void SimplelsfQ( - float *lsfdeq, /* (o) dequantized lsf coefficients - (dimension FILTERORDER) */ - int *index, /* (o) quantization index */ - float *lsf, /* (i) the lsf coefficient vector to be - quantized (dimension FILTERORDER ) */ - int lpc_n /* (i) number of lsf sets to quantize */ - ){ - /* Quantize first LSF with memoryless split VQ */ - SplitVQ(lsfdeq, index, lsf, lsfCbTbl, LSF_NSPLIT, - dim_lsfCbTbl, size_lsfCbTbl); - - if (lpc_n==2) { - /* Quantize second LSF with memoryless split VQ */ - SplitVQ(lsfdeq + LPC_FILTERORDER, index + LSF_NSPLIT, - lsf + LPC_FILTERORDER, lsfCbTbl, LSF_NSPLIT, - dim_lsfCbTbl, size_lsfCbTbl); - } - } - - /*----------------------------------------------------------------* - * lpc encoder - *---------------------------------------------------------------*/ - - void LPCencode( - float *syntdenum, /* (i/o) synthesis filter coefficients - before/after encoding */ - float *weightdenum, /* (i/o) weighting denumerator - coefficients before/after - encoding */ - int *lsf_index, /* (o) lsf quantization index */ - float *data, /* (i) lsf coefficients to quantize */ - iLBC_Enc_Inst_t *iLBCenc_inst - /* (i/o) the encoder state structure */ - ){ - float lsf[LPC_FILTERORDER * LPC_N_MAX]; - float lsfdeq[LPC_FILTERORDER * LPC_N_MAX]; - int change=0; - - SimpleAnalysis(lsf, data, iLBCenc_inst); - SimplelsfQ(lsfdeq, lsf_index, lsf, iLBCenc_inst->lpc_n); - - - -Andersen, et al. Experimental [Page 171] - -RFC 3951 Internet Low Bit Rate Codec December 2004 - - - change=LSF_check(lsfdeq, LPC_FILTERORDER, iLBCenc_inst->lpc_n); - SimpleInterpolateLSF(syntdenum, weightdenum, - lsf, lsfdeq, iLBCenc_inst->lsfold, - iLBCenc_inst->lsfdeqold, LPC_FILTERORDER, iLBCenc_inst); - } - -A.39. lsf.h - - /****************************************************************** - - iLBC Speech Coder ANSI-C Source Code - - lsf.h - - Copyright (C) The Internet Society (2004). - All Rights Reserved. - - ******************************************************************/ - - #ifndef __iLBC_LSF_H - #define __iLBC_LSF_H - - void a2lsf( - float *freq,/* (o) lsf coefficients */ - float *a /* (i) lpc coefficients */ - ); - - void lsf2a( - float *a_coef, /* (o) lpc coefficients */ - float *freq /* (i) lsf coefficients */ - ); - - #endif - -A.40. lsf.c - - /****************************************************************** - - iLBC Speech Coder ANSI-C Source Code - - lsf.c - - Copyright (C) The Internet Society (2004). - All Rights Reserved. - - ******************************************************************/ - - #include - - - -Andersen, et al. Experimental [Page 172] - -RFC 3951 Internet Low Bit Rate Codec December 2004 - - - #include - - #include "iLBC_define.h" - - /*----------------------------------------------------------------* - * conversion from lpc coefficients to lsf coefficients - *---------------------------------------------------------------*/ - - void a2lsf( - float *freq,/* (o) lsf coefficients */ - float *a /* (i) lpc coefficients */ - ){ - float steps[LSF_NUMBER_OF_STEPS] = - {(float)0.00635, (float)0.003175, (float)0.0015875, - (float)0.00079375}; - float step; - int step_idx; - int lsp_index; - float p[LPC_HALFORDER]; - float q[LPC_HALFORDER]; - float p_pre[LPC_HALFORDER]; - float q_pre[LPC_HALFORDER]; - float old_p, old_q, *old; - float *pq_coef; - float omega, old_omega; - int i; - float hlp, hlp1, hlp2, hlp3, hlp4, hlp5; - - for (i=0; i= 0.5)){ - - if (step_idx == (LSF_NUMBER_OF_STEPS - 1)){ - - if (fabs(hlp5) >= fabs(*old)) { - freq[lsp_index] = omega - step; - } else { - freq[lsp_index] = omega; - } - - - -Andersen, et al. Experimental [Page 174] - -RFC 3951 Internet Low Bit Rate Codec December 2004 - - - - - if ((*old) >= 0.0){ - *old = (float)-1.0 * FLOAT_MAX; - } else { - *old = FLOAT_MAX; - } - - omega = old_omega; - step_idx = 0; - - step_idx = LSF_NUMBER_OF_STEPS; - } else { - - if (step_idx == 0) { - old_omega = omega; - } - - step_idx++; - omega -= steps[step_idx]; - - /* Go back one grid step */ - - step = steps[step_idx]; - } - } else { - - /* increment omega until they are of different sign, - and we know there is at least one root between omega - and old_omega */ - *old = hlp5; - omega += step; - } - } - } - - for (i = 0; i= 0.5)){ - - - if (freq[0] <= 0.0) { - freq[0] = (float)0.022; - } - - - if (freq[LPC_FILTERORDER - 1] >= 0.5) { - freq[LPC_FILTERORDER - 1] = (float)0.499; - } - - hlp = (freq[LPC_FILTERORDER - 1] - freq[0]) / - (float) (LPC_FILTERORDER - 1); - - for (i=1; i - #include - - #include "iLBC_define.h" - #include "constants.h" - #include "helpfun.h" - #include "string.h" - - /*----------------------------------------------------------------* - * splitting an integer into first most significant bits and - * remaining least significant bits - *---------------------------------------------------------------*/ - - void packsplit( - int *index, /* (i) the value to split */ - int *firstpart, /* (o) the value specified by most - significant bits */ - int *rest, /* (o) the value specified by least - significant bits */ - - - -Andersen, et al. Experimental [Page 179] - -RFC 3951 Internet Low Bit Rate Codec December 2004 - - - int bitno_firstpart, /* (i) number of bits in most - significant part */ - int bitno_total /* (i) number of bits in full range - of value */ - ){ - int bitno_rest = bitno_total-bitno_firstpart; - - *firstpart = *index>>(bitno_rest); - *rest = *index-(*firstpart<<(bitno_rest)); - } - - /*----------------------------------------------------------------* - * combining a value corresponding to msb's with a value - * corresponding to lsb's - *---------------------------------------------------------------*/ - - void packcombine( - int *index, /* (i/o) the msb value in the - combined value out */ - int rest, /* (i) the lsb value */ - int bitno_rest /* (i) the number of bits in the - lsb part */ - ){ - *index = *index<0) { - - /* Jump to the next byte if end of this byte is reached*/ - - if (*pos==8) { - *pos=0; - (*bitstream)++; - **bitstream=0; - } - - posLeft=8-(*pos); - - /* Insert index into the bitstream */ - - if (bitno <= posLeft) { - **bitstream |= (unsigned char)(index<<(posLeft-bitno)); - *pos+=bitno; - bitno=0; - } else { - **bitstream |= (unsigned char)(index>>(bitno-posLeft)); - - *pos=8; - index-=((index>>(bitno-posLeft))<<(bitno-posLeft)); - - bitno-=posLeft; - } - } - } - - /*----------------------------------------------------------------* - * unpacking of bits from bitstream, i.e., vector of bytes - *---------------------------------------------------------------*/ - - void unpack( - unsigned char **bitstream, /* (i/o) on entrance pointer to - place in bitstream to - unpack new data from, on - exit pointer to place in - bitstream to unpack future - data from */ - int *index, /* (o) resulting value */ - int bitno, /* (i) number of bits used to - represent the value */ - int *pos /* (i/o) read position in the - current byte */ - - - -Andersen, et al. Experimental [Page 181] - -RFC 3951 Internet Low Bit Rate Codec December 2004 - - - ){ - int BitsLeft; - - *index=0; - - while (bitno>0) { - - /* move forward in bitstream when the end of the - byte is reached */ - - if (*pos==8) { - *pos=0; - (*bitstream)++; - } - - BitsLeft=8-(*pos); - - /* Extract bits to index */ - - if (BitsLeft>=bitno) { - *index+=((((**bitstream)<<(*pos)) & 0xFF)>>(8-bitno)); - - *pos+=bitno; - bitno=0; - } else { - - if ((8-bitno)>0) { - *index+=((((**bitstream)<<(*pos)) & 0xFF)>> - (8-bitno)); - *pos=8; - } else { - *index+=(((int)(((**bitstream)<<(*pos)) & 0xFF))<< - (bitno-8)); - *pos=8; - } - bitno-=BitsLeft; - } - } - } - -A.43. StateConstructW.h - - /****************************************************************** - - iLBC Speech Coder ANSI-C Source Code - - StateConstructW.h - - - - -Andersen, et al. Experimental [Page 182] - -RFC 3951 Internet Low Bit Rate Codec December 2004 - - - Copyright (C) The Internet Society (2004). - All Rights Reserved. - - ******************************************************************/ - - #ifndef __iLBC_STATECONSTRUCTW_H - #define __iLBC_STATECONSTRUCTW_H - - void StateConstructW( - int idxForMax, /* (i) 6-bit index for the quantization of - max amplitude */ - int *idxVec, /* (i) vector of quantization indexes */ - float *syntDenum, /* (i) synthesis filter denumerator */ - float *out, /* (o) the decoded state vector */ - int len /* (i) length of a state vector */ - ); - - #endif - -A.44. StateConstructW.c - - /****************************************************************** - - iLBC Speech Coder ANSI-C Source Code - - StateConstructW.c - - Copyright (C) The Internet Society (2004). - All Rights Reserved. - - ******************************************************************/ - - #include - #include - - #include "iLBC_define.h" - #include "constants.h" - #include "filter.h" - - /*----------------------------------------------------------------* - * decoding of the start state - *---------------------------------------------------------------*/ - - void StateConstructW( - int idxForMax, /* (i) 6-bit index for the quantization of - max amplitude */ - int *idxVec, /* (i) vector of quantization indexes */ - float *syntDenum, /* (i) synthesis filter denumerator */ - - - -Andersen, et al. Experimental [Page 183] - -RFC 3951 Internet Low Bit Rate Codec December 2004 - - - float *out, /* (o) the decoded state vector */ - int len /* (i) length of a state vector */ - ){ - float maxVal, tmpbuf[LPC_FILTERORDER+2*STATE_LEN], *tmp, - numerator[LPC_FILTERORDER+1]; - float foutbuf[LPC_FILTERORDER+2*STATE_LEN], *fout; - int k,tmpi; - - /* decoding of the maximum value */ - - maxVal = state_frgqTbl[idxForMax]; - maxVal = (float)pow(10,maxVal)/(float)4.5; - - /* initialization of buffers and coefficients */ - - memset(tmpbuf, 0, LPC_FILTERORDER*sizeof(float)); - memset(foutbuf, 0, LPC_FILTERORDER*sizeof(float)); - for (k=0; k - #include - - #include "iLBC_define.h" - #include "constants.h" - #include "filter.h" - #include "helpfun.h" - - /*----------------------------------------------------------------* - * predictive noise shaping encoding of scaled start state - * (subrutine for StateSearchW) - *---------------------------------------------------------------*/ - - void AbsQuantW( - iLBC_Enc_Inst_t *iLBCenc_inst, - /* (i) Encoder instance */ - float *in, /* (i) vector to encode */ - float *syntDenum, /* (i) denominator of synthesis filter */ - float *weightDenum, /* (i) denominator of weighting filter */ - int *out, /* (o) vector of quantizer indexes */ - int len, /* (i) length of vector to encode and - vector of quantizer indexes */ - int state_first /* (i) position of start state in the - 80 vec */ - ){ - float *syntOut; - float syntOutBuf[LPC_FILTERORDER+STATE_SHORT_LEN_30MS]; - float toQ, xq; - int n; - int index; - - /* initialization of buffer for filtering */ - - memset(syntOutBuf, 0, LPC_FILTERORDER*sizeof(float)); - - - - -Andersen, et al. Experimental [Page 186] - -RFC 3951 Internet Low Bit Rate Codec December 2004 - - - /* initialization of pointer for filtering */ - - syntOut = &syntOutBuf[LPC_FILTERORDER]; - - /* synthesis and weighting filters on input */ - - if (state_first) { - AllPoleFilter (in, weightDenum, SUBL, LPC_FILTERORDER); - } else { - AllPoleFilter (in, weightDenum, - iLBCenc_inst->state_short_len-SUBL, - LPC_FILTERORDER); - } - - /* encoding loop */ - - for (n=0; nstate_short_len-SUBL))) { - syntDenum += (LPC_FILTERORDER+1); - weightDenum += (LPC_FILTERORDER+1); - - /* synthesis and weighting filters on input */ - AllPoleFilter (&in[n], weightDenum, len-n, - LPC_FILTERORDER); - - } - - /* prediction of synthesized and weighted input */ - - syntOut[n] = 0.0; - AllPoleFilter (&syntOut[n], weightDenum, 1, - LPC_FILTERORDER); - - /* quantization */ - - toQ = in[n]-syntOut[n]; - - - -Andersen, et al. Experimental [Page 187] - -RFC 3951 Internet Low Bit Rate Codec December 2004 - - - sort_sq(&xq, &index, toQ, state_sq3Tbl, 8); - out[n]=index; - syntOut[n] = state_sq3Tbl[out[n]]; - - /* update of the prediction filter */ - - AllPoleFilter(&syntOut[n], weightDenum, 1, - LPC_FILTERORDER); - } - } - - /*----------------------------------------------------------------* - * encoding of start state - *---------------------------------------------------------------*/ - - void StateSearchW( - iLBC_Enc_Inst_t *iLBCenc_inst, - /* (i) Encoder instance */ - float *residual,/* (i) target residual vector */ - float *syntDenum, /* (i) lpc synthesis filter */ - float *weightDenum, /* (i) weighting filter denuminator */ - int *idxForMax, /* (o) quantizer index for maximum - amplitude */ - int *idxVec, /* (o) vector of quantization indexes */ - int len, /* (i) length of all vectors */ - int state_first /* (i) position of start state in the - 80 vec */ - ){ - float dtmp, maxVal; - float tmpbuf[LPC_FILTERORDER+2*STATE_SHORT_LEN_30MS]; - float *tmp, numerator[1+LPC_FILTERORDER]; - float foutbuf[LPC_FILTERORDER+2*STATE_SHORT_LEN_30MS], *fout; - int k; - float qmax, scal; - - /* initialization of buffers and filter coefficients */ - - memset(tmpbuf, 0, LPC_FILTERORDER*sizeof(float)); - memset(foutbuf, 0, LPC_FILTERORDER*sizeof(float)); - for (k=0; k maxVal*maxVal){ - maxVal = fout[k]; - } - } - maxVal=(float)fabs(maxVal); - - /* encoding of the maximum amplitude value */ - - if (maxVal < 10.0) { - maxVal = 10.0; - } - maxVal = (float)log10(maxVal); - sort_sq(&dtmp, idxForMax, maxVal, state_frgqTbl, 64); - - /* decoding of the maximum amplitude representation value, - and corresponding scaling of start state */ - - maxVal=state_frgqTbl[*idxForMax]; - qmax = (float)pow(10,maxVal); - scal = (float)(4.5)/qmax; - for (k=0; k | - | 20 ms frame | 30 ms frame | - ----------------------------------+---------------+---------------+ - Split 1 | 6 <6,0,0> | 6 <6,0,0> | - LSF 1 Split 2 | 7 <7,0,0> | 7 <7,0,0> | - LSF Split 3 | 7 <7,0,0> | 7 <7,0,0> | - ------------------+---------------+---------------+ - Split 1 | NA (Not Appl.)| 6 <6,0,0> | - LSF 2 Split 2 | NA | 7 <7,0,0> | - Split 3 | NA | 7 <7,0,0> | - ------------------+---------------+---------------+ - Sum | 20 <20,0,0> | 40 <40,0,0> | - ----------------------------------+---------------+---------------+ - Block Class. | 2 <2,0,0> | 3 <3,0,0> | - ----------------------------------+---------------+---------------+ - Position 22 sample segment | 1 <1,0,0> | 1 <1,0,0> | - ----------------------------------+---------------+---------------+ - Scale Factor State Coder | 6 <6,0,0> | 6 <6,0,0> | - ----------------------------------+---------------+---------------+ - Sample 0 | 3 <0,1,2> | 3 <0,1,2> | - Quantized Sample 1 | 3 <0,1,2> | 3 <0,1,2> | - Residual : | : : | : : | - State : | : : | : : | - Samples : | : : | : : | - Sample 56 | 3 <0,1,2> | 3 <0,1,2> | - Sample 57 | NA | 3 <0,1,2> | - ------------------+---------------+---------------+ - Sum | 171 <0,57,114>| 174 <0,58,116>| - ----------------------------------+---------------+---------------+ - Stage 1 | 7 <6,0,1> | 7 <4,2,1> | - CB for 22/23 Stage 2 | 7 <0,0,7> | 7 <0,0,7> | - sample block Stage 3 | 7 <0,0,7> | 7 <0,0,7> | - ------------------+---------------+---------------+ - Sum | 21 <6,0,15> | 21 <4,2,15> | - ----------------------------------+---------------+---------------+ - Stage 1 | 5 <2,0,3> | 5 <1,1,3> | - Gain for 22/23 Stage 2 | 4 <1,1,2> | 4 <1,1,2> | - sample block Stage 3 | 3 <0,0,3> | 3 <0,0,3> | - ------------------+---------------+---------------+ - Sum | 12 <3,1,8> | 12 <2,2,8> | - ----------------------------------+---------------+---------------+ - Stage 1 | 8 <7,0,1> | 8 <6,1,1> | - sub-block 1 Stage 2 | 7 <0,0,7> | 7 <0,0,7> | - Stage 3 | 7 <0,0,7> | 7 <0,0,7> | - ------------------+---------------+---------------+ - - - -Duric & Andersen Experimental [Page 5] - -RFC 3952 RTP Payload Format for iLBC Speech December 2004 - - - Stage 1 | 8 <0,0,8> | 8 <0,7,1> | - sub-block 2 Stage 2 | 8 <0,0,8> | 8 <0,0,8> | - Indices Stage 3 | 8 <0,0,8> | 8 <0,0,8> | - for CB ------------------+---------------+---------------+ - sub-blocks Stage 1 | NA | 8 <0,7,1> | - sub-block 3 Stage 2 | NA | 8 <0,0,8> | - Stage 3 | NA | 8 <0,0,8> | - ------------------+---------------+---------------+ - Stage 1 | NA | 8 <0,7,1> | - sub-block 4 Stage 2 | NA | 8 <0,0,8> | - Stage 3 | NA | 8 <0,0,8> | - ------------------+---------------+---------------+ - Sum | 46 <7,0,39> | 94 <6,22,66> | - ----------------------------------+---------------+---------------+ - Stage 1 | 5 <1,2,2> | 5 <1,2,2> | - sub-block 1 Stage 2 | 4 <1,1,2> | 4 <1,2,1> | - Stage 3 | 3 <0,0,3> | 3 <0,0,3> | - ------------------+---------------+---------------+ - Stage 1 | 5 <1,1,3> | 5 <0,2,3> | - sub-block 2 Stage 2 | 4 <0,2,2> | 4 <0,2,2> | - Stage 3 | 3 <0,0,3> | 3 <0,0,3> | - Gains for ------------------+---------------+---------------+ - sub-blocks Stage 1 | NA | 5 <0,1,4> | - sub-block 3 Stage 2 | NA | 4 <0,1,3> | - Stage 3 | NA | 3 <0,0,3> | - ------------------+---------------+---------------+ - Stage 1 | NA | 5 <0,1,4> | - sub-block 4 Stage 2 | NA | 4 <0,1,3> | - Stage 3 | NA | 3 <0,0,3> | - ------------------+---------------+---------------+ - Sum | 24 <3,6,15> | 48 <2,12,34> | - ------------------------------------------------------------------- - Empty frame indicator | 1 <0,0,1> | 1 <0,0,1> | - ------------------------------------------------------------------- - SUM 304 <48,64,192> 400 <64,96,240> - - Table 3.1 The bitstream definition for iLBC. - - When packetized into the payload, all the class 1 bits MUST be sorted - in order (from top and down) as they were specified in the table. - Additionally, all the class 2 bits MUST be sorted (from top and down) - and all the class 3 bits MUST be sorted in the same sequential order. - -3.2. Multiple iLBC frames in a RTP packet - - More than one iLBC frame may be included in a single RTP packet by a - sender. - - - - -Duric & Andersen Experimental [Page 6] - -RFC 3952 RTP Payload Format for iLBC Speech December 2004 - - - It is important to observe that senders have the following additional - restrictions: - - o SHOULD NOT include more iLBC frames in a single RTP packet than - will fit in the MTU of the RTP transport protocol. - - o Frames MUST NOT be split between RTP packets. - - o Frames of the different modes (20 ms and 30 ms) MUST NOT be - included within the same packet. - - It is RECOMMENDED that the number of frames contained within an RTP - packet are consistent with the application. For example, in - telephony and other real time applications where delay is important, - the delay is lower depending on the amount of frames per packet - (i.e., fewer frames per packet, the lower the delay). Whereas for - bandwidth constrained links or delay insensitive streaming messaging - application, one or more frames per packet would be acceptable. - - Information describing the number of frames contained in an RTP - packet is not transmitted as part of the RTP payload. The way to - determine the number of iLBC frames is to count the total number of - octets within the RTP packet, and divide the octet count by the - number of expected octets per frame (32/50 per frame). - -4. IANA Considerations - - One new MIME sub-type as described in this section has been - registered. - -4.1. Storage Mode - - The storage mode is used for storing speech frames (e.g., as a file - or email attachment). - - +------------------+ - | Header | - +------------------+ - | Speech frame 1 | - +------------------+ - : : - +------------------+ - | Speech frame n | - +------------------+ - - Figure 2, Storage format diagram - - - - - -Duric & Andersen Experimental [Page 7] - -RFC 3952 RTP Payload Format for iLBC Speech December 2004 - - - The file begins with a header that includes only a magic number to - identify that it is an iLBC file. - - The magic number for iLBC file MUST correspond to the ASCII character - string: - - o for 30 ms frame size mode:"#!iLBC30\n", or "0x23 0x21 0x69 - 0x4C 0x42 0x43 0x33 0x30 0x0A" in hexadecimal form, - - o for 20 ms frame size mode:"#!iLBC20\n", or "0x23 0x21 0x69 - 0x4C 0x42 0x43 0x32 0x30 0x0A" in hexadecimal form. - - After the header, follow the speech frames in consecutive order. - - Speech frames lost in transmission MUST be stored as "empty frames", - as defined in [1]. - -4.2. MIME Registration of iLBC - - MIME media type name: audio - - MIME subtype: iLBC - - Optional parameters: - - All of the parameters does apply for RTP transfer only. - - maxptime:The maximum amount of media which can be encapsulated in - each packet, expressed as time in milliseconds. The time - SHALL be calculated as the sum of the time the media present - in the packet represents. The time SHOULD be a multiple of - the frame size. This attribute is probably only meaningful - for audio data, but may be used with other media types if it - makes sense. It is a media attribute, and is not dependent - on charset. Note that this attribute was introduced after - RFC 2327, and non updated implementations will ignore this - attribute. - - mode: The iLBC operating frame mode (20 or 30 ms) that will be - encapsulated in each packet. Values can be 0, 20 and 30 - (where 0 is reserved, 20 stands for preferred 20 ms frame - size and 30 stands for preferred 30 ms frame size). - - ptime: Defined as usual for RTP audio (see [5]). - - Encoding considerations: - This type is defined for transfer via both RTP (RFC 3550) - and stored-file methods as described in Section 4.1, of RFC - - - -Duric & Andersen Experimental [Page 8] - -RFC 3952 RTP Payload Format for iLBC Speech December 2004 - - - 3952. Audio data is binary data, and must be encoded for - non-binary transport; the Base64 encoding is suitable for - email. - - Security considerations: - See Section 6 of RFC 3952. - - Public specification: - Please refer to RFC 3951 [1]. - - Additional information: - The following applies to stored-file transfer methods: - - Magic number: - ASCII character string for: - o 30 ms frame size mode "#!iLBC30\n" (or 0x23 0x21 - 0x69 0x4C 0x42 0x43 0x33 0x30 0x0A in hexadecimal) - o 20 ms frame size mode "#!iLBC20\n" (or 0x23 0x21 - 0x69 0x4C 0x42 0x43 0x32 0x30 0x0A in hexadecimal) - - File extensions: lbc, LBC - Macintosh file type code: none - Object identifier or OID: none - - Person & email address to contact for further information: - alan.duric@telio.no - - Intended usage: COMMON. - It is expected that many VoIP applications will use this - type. - - Author/Change controller: - alan.duric@telio.no - IETF Audio/Video transport working group - -5. Mapping To SDP Parameters - - The information carried in the MIME media type specification has a - specific mapping to fields in the Session Description Protocol (SDP) - [5], which is commonly used to describe RTP sessions. When SDP is - used to specify sessions employing the iLBC codec, the mapping is as - follows: - - o The MIME type ("audio") goes in SDP "m=" as the media name. - - o The MIME subtype (payload format name) goes in SDP "a=rtpmap" as - the encoding name. - - - - -Duric & Andersen Experimental [Page 9] - -RFC 3952 RTP Payload Format for iLBC Speech December 2004 - - - o The parameters "ptime" and "maxptime" go in the SDP "a=ptime" and - "a=maxptime" attributes, respectively. - - o The parameter "mode" goes in the SDP "a=fmtp" attribute by copying - it directly from the MIME media type string as "mode=value". - - When conveying information by SDP, the encoding name SHALL be "iLBC" - (the same as the MIME subtype). - - An example of the media representation in SDP for describing iLBC - might be: - - m=audio 49120 RTP/AVP 97 - a=rtpmap:97 iLBC/8000 - - If 20 ms frame size mode is used, remote iLBC encoder SHALL receive - "mode" parameter in the SDP "a=fmtp" attribute by copying them - directly from the MIME media type string as a semicolon separated - with parameter=value, where parameter is "mode", and values can be 0 - and 20 (where 0 is reserved and 20 stands for preferred 20 ms frame - size). An example of the media representation in SDP for describing - iLBC when 20 ms frame size mode is used might be: - - m=audio 49120 RTP/AVP 97 - a=rtpmap:97 iLBC/8000 - a=fmtp:97 mode=20 - - It is important to emphasize the bi-directional character of the - "mode" parameter - both sides of a bi-directional session MUST use - the same "mode" value. - - The offer contains the preferred mode of the offerer. The answerer - may agree to that mode by including the same mode in the answer, or - may include a different mode. The resulting mode used by both - parties SHALL be the lower of the bandwidth modes in the offer and - answer. - - That is, an offer of "mode=20" receiving an answer of "mode=30" will - result in "mode=30" being used by both participants. Similarly, an - offer of "mode=30" and an answer of "mode=20" will result in - "mode=30" being used by both participants. - - This is important when one end point utilizes a bandwidth constrained - link (e.g., 28.8k modem link or slower), where only the lower frame - size will work. - - - - - - -Duric & Andersen Experimental [Page 10] - -RFC 3952 RTP Payload Format for iLBC Speech December 2004 - - - Parameter ptime can not be used for the purpose of specifying iLBC - operating mode, due to fact that for the certain values it will be - impossible to distinguish which mode is about to be used (e.g., when - ptime=60, it would be impossible to distinguish if packet is carrying - 2 frames of 30 ms or 3 frames of 20 ms, etc.). - - Note that the payload format (encoding) names are commonly shown in - upper case. MIME subtypes are commonly shown in lower case. These - names are case-insensitive in both places. Similarly, parameter - names are case-insensitive both in MIME types and in the default - mapping to the SDP a=fmtp attribute - -6. Security Considerations - - RTP packets using the payload format defined in this specification - are subject to the general security considerations discussed in [3] - and any appropriate profile (e.g., [4]). - - As this format transports encoded speech, the main security issues - include confidentiality and authentication of the speech itself. The - payload format itself does not have any built-in security mechanisms. - Confidentiality of the media streams is achieved by encryption, - therefore external mechanisms, such as SRTP [6], MAY be used for that - purpose. The data compression used with this payload format is - applied end-to-end; hence encryption may be performed after - compression with no conflict between the two operations. - - A potential denial-of-service threat exists for data encoding using - compression techniques that have non-uniform receiver-end - computational load. The attacker can inject pathological datagrams - into the stream which are complex to decode and cause the receiver to - become overloaded. However, the encodings covered in this document - do not exhibit any significant non-uniformity. - -7. References - -7.1. Normative References - - [1] Andersen, S., Duric, A., Astrom, H., Hagen, R., Kleijn, W., and - J. Linden, "Internet Low Bit Rate Codec (iLBC)", RFC 3951, - December 2004. - - [2] Bradner, S., "Key words for use in RFCs to Indicate Requirement - Levels", BCP 14, RFC 2119, March 1997. - - [3] Schulzrinne, H., Casner, S., Frederick, R., and V. Jacobson, - "RTP: A Transport Protocol for Real-Time Applications", STD 64, - RFC 3550, July 2003. - - - -Duric & Andersen Experimental [Page 11] - -RFC 3952 RTP Payload Format for iLBC Speech December 2004 - - - [4] Schulzrinne, H. and S. Casner, "RTP Profile for Audio and Video - Conferences with Minimal Control", STD 65, RFC 3551, July 2003. - - [5] Handley, M. and V. Jacobson, "SDP: Session Description - Protocol", RFC 2327, April 1998. - - [6] Baugher, M., McGrew, D., Naslund, M., Carrara, E., and K. - Norrman, "The Secure Real-time Transport Protocol", RFC 3711, - March 2004. - -7.2. Informative References - - [7] ITU-T Recommendation G.711, available online from the ITU - bookstore at http://www.itu.int. - -8. Acknowledgements - - Henry Sinnreich, Patrik Faltstrom, Alan Johnston and Jean-Francois - Mule for great support of the iLBC initiative and for valuable - feedback and comments. - -Authors' Addresses - - Alan Duric - Telio AS - Stoperigt. 2 - Oslo, N-0250 - Norway - - Phone: +47 21673505 - EMail: alan.duric@telio.no - - - Soren Vang Andersen - Department of Communication Technology - Aalborg University - Fredrik Bajers Vej 7A - 9200 Aalborg - Denmark - - Phone: ++45 9 6358627 - EMail: sva@kom.auc.dk - - - - - - - - - -Duric & Andersen Experimental [Page 12] - -RFC 3952 RTP Payload Format for iLBC Speech December 2004 - - -Full Copyright Statement - - Copyright (C) The Internet Society (2004). - - This document is subject to the rights, licenses and restrictions - contained in BCP 78, and except as set forth therein, the authors - retain all their rights. - - This document and the information contained herein are provided on an - "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS - OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY AND THE INTERNET - ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS OR IMPLIED, - INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE - INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED - WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. - -Intellectual Property - - The IETF takes no position regarding the validity or scope of any - Intellectual Property Rights or other rights that might be claimed to - pertain to the implementation or use of the technology described in - this document or the extent to which any license under such rights - might or might not be available; nor does it represent that it has - made any independent effort to identify any such rights. Information - on the IETF's procedures with respect to rights in IETF Documents can - be found in BCP 78 and BCP 79. - - Copies of IPR disclosures made to the IETF Secretariat and any - assurances of licenses to be made available, or the result of an - attempt made to obtain a general license or permission for the use of - such proprietary rights by implementers or users of this - specification can be obtained from the IETF on-line IPR repository at - http://www.ietf.org/ipr. - - The IETF invites any interested party to bring to its attention any - copyrights, patents or patent applications, or other proprietary - rights that may cover technology that may be required to implement - this standard. Please address the information to the IETF at ietf- - ipr@ietf.org. - - -Acknowledgement - - Funding for the RFC Editor function is currently provided by the - Internet Society. - - - - - - -Duric & Andersen Experimental [Page 13] -