72 lines
2.0 KiB
C
72 lines
2.0 KiB
C
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/*
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* Copyright (c) 2011 The WebRTC project authors. All Rights Reserved.
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*
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* Use of this source code is governed by a BSD-style license
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* that can be found in the LICENSE file in the root of the source
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* tree. An additional intellectual property rights grant can be found
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* in the file PATENTS. All contributing project authors may
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* be found in the AUTHORS file in the root of the source tree.
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*/
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/******************************************************************
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iLBC Speech Coder ANSI-C Source Code
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WebRtcIlbcfix_LsfCheck.c
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******************************************************************/
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#include "defines.h"
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#include "constants.h"
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/*----------------------------------------------------------------*
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* check for stability of lsf coefficients
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*---------------------------------------------------------------*/
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int WebRtcIlbcfix_LsfCheck(
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WebRtc_Word16 *lsf, /* LSF parameters */
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int dim, /* dimension of LSF */
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int NoAn) /* No of analysis per frame */
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{
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int k,n,m, Nit=2, change=0,pos;
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const WebRtc_Word16 eps=319; /* 0.039 in Q13 (50 Hz)*/
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const WebRtc_Word16 eps2=160; /* eps/2.0 in Q13;*/
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const WebRtc_Word16 maxlsf=25723; /* 3.14; (4000 Hz)*/
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const WebRtc_Word16 minlsf=82; /* 0.01; (0 Hz)*/
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/* LSF separation check*/
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for (n=0;n<Nit;n++) { /* Run through a 2 times */
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for (m=0;m<NoAn;m++) { /* Number of analyses per frame */
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for (k=0;k<(dim-1);k++) {
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pos=m*dim+k;
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/* Seperate coefficients with a safety margin of 50 Hz */
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if ((lsf[pos+1]-lsf[pos])<eps) {
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if (lsf[pos+1]<lsf[pos]) {
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lsf[pos+1]= lsf[pos]+eps2;
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lsf[pos]= lsf[pos+1]-eps2;
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} else {
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lsf[pos]-=eps2;
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lsf[pos+1]+=eps2;
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}
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change=1;
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}
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/* Limit minimum and maximum LSF */
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if (lsf[pos]<minlsf) {
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lsf[pos]=minlsf;
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change=1;
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}
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if (lsf[pos]>maxlsf) {
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lsf[pos]=maxlsf;
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change=1;
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}
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}
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}
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}
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return change;
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}
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