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/*
* Copyright (c) 2011 The WebRTC project authors. All Rights Reserved.
*
* Use of this source code is governed by a BSD-style license
* that can be found in the LICENSE file in the root of the source
* tree. An additional intellectual property rights grant can be found
* in the file PATENTS. All contributing project authors may
* be found in the AUTHORS file in the root of the source tree.
*/
/******************************************************************
iLBC Speech Coder ANSI-C Source Code
WebRtcIlbcfix_LsfCheck.c
******************************************************************/
#include "modules/audio_coding/codecs/ilbc/lsf_check.h"
#include "modules/audio_coding/codecs/ilbc/constants.h"
#include "modules/audio_coding/codecs/ilbc/defines.h"
/*----------------------------------------------------------------*
* check for stability of lsf coefficients
*---------------------------------------------------------------*/
int WebRtcIlbcfix_LsfCheck(
int16_t *lsf, /* LSF parameters */
int dim, /* dimension of LSF */
int NoAn) /* No of analysis per frame */
{
int k,n,m, Nit=2, change=0,pos;
const int16_t eps=319; /* 0.039 in Q13 (50 Hz)*/
const int16_t eps2=160; /* eps/2.0 in Q13;*/
const int16_t maxlsf=25723; /* 3.14; (4000 Hz)*/
const int16_t minlsf=82; /* 0.01; (0 Hz)*/
/* LSF separation check*/
for (n=0;n<Nit;n++) { /* Run through a 2 times */
for (m=0;m<NoAn;m++) { /* Number of analyses per frame */
for (k=0;k<(dim-1);k++) {
pos=m*dim+k;
/* Seperate coefficients with a safety margin of 50 Hz */
if ((lsf[pos+1]-lsf[pos])<eps) {
if (lsf[pos+1]<lsf[pos]) {
lsf[pos+1]= lsf[pos]+eps2;
lsf[pos]= lsf[pos+1]-eps2;
} else {
lsf[pos]-=eps2;
lsf[pos+1]+=eps2;
}
change=1;
}
/* Limit minimum and maximum LSF */
if (lsf[pos]<minlsf) {
lsf[pos]=minlsf;
change=1;
}
if (lsf[pos]>maxlsf) {
lsf[pos]=maxlsf;
change=1;
}
}
}
}
return change;
}
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