f3035f2bc7
The formatting of OD_UNIFORM_CDFS_Q15[] in entcode.c is helpful for for understanding what is contained in the array (e.g., the uniform probability distributions of small sizes 2 through 16). This patch reverts the change made in f4b2926d and adds linter hints to ignore the formatting. Change-Id: I2ad9fe6673b86e6067cb97b40f0f0e69a119cdf5
94 lines
4.2 KiB
C
94 lines
4.2 KiB
C
/*Daala video codec
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Copyright (c) 2001-2012 Daala project contributors. All rights reserved.
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Redistribution and use in source and binary forms, with or without
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modification, are permitted provided that the following conditions are met:
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- Redistributions of source code must retain the above copyright notice, this
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list of conditions and the following disclaimer.
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- Redistributions in binary form must reproduce the above copyright notice,
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this list of conditions and the following disclaimer in the documentation
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and/or other materials provided with the distribution.
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THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
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AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
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DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE
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FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
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SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
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CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
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OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
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OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.*/
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#ifdef HAVE_CONFIG_H
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#include "./config.h"
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#endif
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#include "aom_dsp/entcode.h"
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/*CDFs for uniform probability distributions of small sizes (2 through 16,
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inclusive).*/
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// clang-format off
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const uint16_t OD_UNIFORM_CDFS_Q15[135] = {
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16384, 32768,
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10923, 21845, 32768,
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8192, 16384, 24576, 32768,
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6554, 13107, 19661, 26214, 32768,
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5461, 10923, 16384, 21845, 27307, 32768,
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4681, 9362, 14043, 18725, 23406, 28087, 32768,
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4096, 8192, 12288, 16384, 20480, 24576, 28672, 32768,
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3641, 7282, 10923, 14564, 18204, 21845, 25486, 29127, 32768,
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3277, 6554, 9830, 13107, 16384, 19661, 22938, 26214, 29491, 32768,
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2979, 5958, 8937, 11916, 14895, 17873, 20852, 23831, 26810, 29789, 32768,
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2731, 5461, 8192, 10923, 13653, 16384, 19115, 21845, 24576, 27307, 30037,
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32768,
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2521, 5041, 7562, 10082, 12603, 15124, 17644, 20165, 22686, 25206, 27727,
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30247, 32768,
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2341, 4681, 7022, 9362, 11703, 14043, 16384, 18725, 21065, 23406, 25746,
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28087, 30427, 32768,
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2185, 4369, 6554, 8738, 10923, 13107, 15292, 17476, 19661, 21845, 24030,
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26214, 28399, 30583, 32768,
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2048, 4096, 6144, 8192, 10240, 12288, 14336, 16384, 18432, 20480, 22528,
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24576, 26624, 28672, 30720, 32768
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};
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// clang-format on
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/*Given the current total integer number of bits used and the current value of
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rng, computes the fraction number of bits used to OD_BITRES precision.
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This is used by od_ec_enc_tell_frac() and od_ec_dec_tell_frac().
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nbits_total: The number of whole bits currently used, i.e., the value
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returned by od_ec_enc_tell() or od_ec_dec_tell().
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rng: The current value of rng from either the encoder or decoder state.
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Return: The number of bits scaled by 2**OD_BITRES.
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This will always be slightly larger than the exact value (e.g., all
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rounding error is in the positive direction).*/
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uint32_t od_ec_tell_frac(uint32_t nbits_total, uint32_t rng) {
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uint32_t nbits;
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int l;
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int i;
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/*To handle the non-integral number of bits still left in the encoder/decoder
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state, we compute the worst-case number of bits of val that must be
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encoded to ensure that the value is inside the range for any possible
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subsequent bits.
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The computation here is independent of val itself (the decoder does not
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even track that value), even though the real number of bits used after
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od_ec_enc_done() may be 1 smaller if rng is a power of two and the
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corresponding trailing bits of val are all zeros.
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If we did try to track that special case, then coding a value with a
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probability of 1/(1 << n) might sometimes appear to use more than n bits.
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This may help explain the surprising result that a newly initialized
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encoder or decoder claims to have used 1 bit.*/
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nbits = nbits_total << OD_BITRES;
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l = 0;
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for (i = OD_BITRES; i-- > 0;) {
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int b;
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rng = rng * rng >> 15;
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b = (int)(rng >> 16);
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l = l << 1 | b;
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rng >>= b;
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}
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return nbits - l;
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}
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