117 lines
2.6 KiB
C
117 lines
2.6 KiB
C
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/******************************************************************
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iLBC Speech Coder ANSI-C Source Code
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gainquant.c
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Copyright (C) The Internet Society (2004).
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All Rights Reserved.
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******************************************************************/
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#include <string.h>
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#include <math.h>
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#include "constants.h"
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#include "filter.h"
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/*----------------------------------------------------------------*
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* quantizer for the gain in the gain-shape coding of residual
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*---------------------------------------------------------------*/
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float gainquant(/* (o) quantized gain value */
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float in, /* (i) gain value */
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float maxIn,/* (i) maximum of gain value */
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int cblen, /* (i) number of quantization indices */
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int *index /* (o) quantization index */
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){
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int i, tindex;
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float minmeasure,measure, *cb, scale;
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/* ensure a lower bound on the scaling factor */
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scale=maxIn;
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if (scale<0.1) {
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scale=(float)0.1;
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}
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/* select the quantization table */
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if (cblen == 8) {
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cb = gain_sq3Tbl;
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} else if (cblen == 16) {
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cb = gain_sq4Tbl;
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} else {
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cb = gain_sq5Tbl;
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}
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/* select the best index in the quantization table */
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minmeasure=10000000.0;
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tindex=0;
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for (i=0; i<cblen; i++) {
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measure=(in-scale*cb[i])*(in-scale*cb[i]);
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if (measure<minmeasure) {
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tindex=i;
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minmeasure=measure;
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}
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}
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*index=tindex;
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/* return the quantized value */
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return scale*cb[tindex];
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}
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/*----------------------------------------------------------------*
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* decoder for quantized gains in the gain-shape coding of
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* residual
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*---------------------------------------------------------------*/
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float gaindequant( /* (o) quantized gain value */
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int index, /* (i) quantization index */
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float maxIn,/* (i) maximum of unquantized gain */
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int cblen /* (i) number of quantization indices */
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){
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float scale;
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/* obtain correct scale factor */
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scale=(float)fabs(maxIn);
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if (scale<0.1) {
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scale=(float)0.1;
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}
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/* select the quantization table and return the decoded value */
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if (cblen==8) {
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return scale*gain_sq3Tbl[index];
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} else if (cblen==16) {
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return scale*gain_sq4Tbl[index];
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}
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else if (cblen==32) {
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return scale*gain_sq5Tbl[index];
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}
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return 0.0;
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}
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