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/******************************************************************
iLBC Speech Coder ANSI-C Source Code
gainquant.c
Copyright (C) The Internet Society (2004).
All Rights Reserved.
******************************************************************/
#include <string.h>
#include <math.h>
#include "constants.h"
#include "gainquant.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<cblen; i++) {
measure=(in-scale*cb[i])*(in-scale*cb[i]);
if (measure<minmeasure) {
tindex=i;
minmeasure=measure;
}
}
*index=tindex;
/* return the quantized value */
return scale*cb[tindex];
}
/*----------------------------------------------------------------*
* decoder for quantized gains in the gain-shape coding of
* residual
*---------------------------------------------------------------*/
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 */
){
float scale;
/* obtain correct scale factor */
scale=(float)fabs(maxIn);
if (scale<0.1) {
scale=(float)0.1;
}
/* select the quantization table and return the decoded value */
if (cblen==8) {
return scale*gain_sq3Tbl[index];
} else if (cblen==16) {
return scale*gain_sq4Tbl[index];
}
else if (cblen==32) {
return scale*gain_sq5Tbl[index];
}
return 0.0;
}
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