159 lines
4.7 KiB
C
159 lines
4.7 KiB
C
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/******************************************************************
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iLBC Speech Coder ANSI-C Source Code
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LPC_decode.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 <math.h>
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#include <string.h>
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#include "helpfun.h"
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#include "lsf.h"
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#include "iLBC_define.h"
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#include "constants.h"
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/*---------------------------------------------------------------*
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* interpolation of lsf coefficients for the decoder
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*--------------------------------------------------------------*/
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void LSFinterpolate2a_dec(
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float *a, /* (o) lpc coefficients for a sub-frame */
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float *lsf1, /* (i) first lsf coefficient vector */
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float *lsf2, /* (i) second lsf coefficient vector */
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float coef, /* (i) interpolation weight */
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int length /* (i) length of lsf vectors */
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){
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float lsftmp[LPC_FILTERORDER];
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interpolate(lsftmp, lsf1, lsf2, coef, length);
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lsf2a(a, lsftmp);
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}
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/*---------------------------------------------------------------*
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* obtain dequantized lsf coefficients from quantization index
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*--------------------------------------------------------------*/
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void SimplelsfDEQ(
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float *lsfdeq, /* (o) dequantized lsf coefficients */
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int *index, /* (i) quantization index */
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int lpc_n /* (i) number of LPCs */
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){
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int i, j, pos, cb_pos;
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/* decode first LSF */
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pos = 0;
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cb_pos = 0;
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for (i = 0; i < LSF_NSPLIT; i++) {
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for (j = 0; j < dim_lsfCbTbl[i]; j++) {
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lsfdeq[pos + j] = lsfCbTbl[cb_pos +
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(long)(index[i])*dim_lsfCbTbl[i] + j];
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}
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pos += dim_lsfCbTbl[i];
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cb_pos += size_lsfCbTbl[i]*dim_lsfCbTbl[i];
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}
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if (lpc_n>1) {
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/* decode last LSF */
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pos = 0;
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cb_pos = 0;
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for (i = 0; i < LSF_NSPLIT; i++) {
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for (j = 0; j < dim_lsfCbTbl[i]; j++) {
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lsfdeq[LPC_FILTERORDER + pos + j] =
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lsfCbTbl[cb_pos +
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(long)(index[LSF_NSPLIT + i])*
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dim_lsfCbTbl[i] + j];
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}
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pos += dim_lsfCbTbl[i];
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cb_pos += size_lsfCbTbl[i]*dim_lsfCbTbl[i];
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}
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}
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}
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/*----------------------------------------------------------------*
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* obtain synthesis and weighting filters form lsf coefficients
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*---------------------------------------------------------------*/
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void DecoderInterpolateLSF(
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float *syntdenum, /* (o) synthesis filter coefficients */
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float *weightdenum, /* (o) weighting denumerator
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coefficients */
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float *lsfdeq, /* (i) dequantized lsf coefficients */
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int length, /* (i) length of lsf coefficient vector */
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iLBC_Dec_Inst_t *iLBCdec_inst
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/* (i) the decoder state structure */
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){
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int i, pos, lp_length;
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float lp[LPC_FILTERORDER + 1], *lsfdeq2;
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lsfdeq2 = lsfdeq + length;
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lp_length = length + 1;
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if (iLBCdec_inst->mode==30) {
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/* sub-frame 1: Interpolation between old and first */
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LSFinterpolate2a_dec(lp, iLBCdec_inst->lsfdeqold, lsfdeq,
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lsf_weightTbl_30ms[0], length);
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memcpy(syntdenum,lp,lp_length*sizeof(float));
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bwexpand(weightdenum, lp, LPC_CHIRP_WEIGHTDENUM,
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lp_length);
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/* sub-frames 2 to 6: interpolation between first
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and last LSF */
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pos = lp_length;
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for (i = 1; i < 6; i++) {
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LSFinterpolate2a_dec(lp, lsfdeq, lsfdeq2,
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lsf_weightTbl_30ms[i], length);
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memcpy(syntdenum + pos,lp,lp_length*sizeof(float));
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bwexpand(weightdenum + pos, lp,
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LPC_CHIRP_WEIGHTDENUM, lp_length);
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pos += lp_length;
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}
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}
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else {
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pos = 0;
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for (i = 0; i < iLBCdec_inst->nsub; i++) {
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LSFinterpolate2a_dec(lp, iLBCdec_inst->lsfdeqold,
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lsfdeq, lsf_weightTbl_20ms[i], length);
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memcpy(syntdenum+pos,lp,lp_length*sizeof(float));
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bwexpand(weightdenum+pos, lp, LPC_CHIRP_WEIGHTDENUM,
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lp_length);
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pos += lp_length;
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}
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}
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/* update memory */
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if (iLBCdec_inst->mode==30)
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memcpy(iLBCdec_inst->lsfdeqold, lsfdeq2,
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length*sizeof(float));
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else
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memcpy(iLBCdec_inst->lsfdeqold, lsfdeq,
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length*sizeof(float));
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}
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