LPCdecode.c

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 /******************************************************************

 iLBC Speech Coder ANSI-C Source Code

 LPC_decode.c

 Copyright (C) The Internet Society (2004).
 All Rights Reserved.

 ******************************************************************/

 #include <math.h>
 #include <string.h>

 #include "helpfun.h"
 #include "lsf.h"
 #include "iLBC_define.h"
 #include "constants.h"

 /*---------------------------------------------------------------*
 * interpolation of lsf coefficients for the decoder
 *--------------------------------------------------------------*/

 void LSFinterpolate2a_dec(
 float *a, /* (o) lpc coefficients for a sub-frame */
 float *lsf1, /* (i) first lsf coefficient vector */
 float *lsf2, /* (i) second lsf coefficient vector */
 float coef, /* (i) interpolation weight */
 int length /* (i) length of lsf vectors */
 ){
 float lsftmp[LPC_FILTERORDER];

 interpolate(lsftmp, lsf1, lsf2, coef, length);
 lsf2a(a, lsftmp);
 }

 /*---------------------------------------------------------------*
 * obtain dequantized lsf coefficients from quantization index
 *--------------------------------------------------------------*/

 void SimplelsfDEQ(
 float *lsfdeq, /* (o) dequantized lsf coefficients */
 int *index, /* (i) quantization index */
 int lpc_n /* (i) number of LPCs */
 ){
 int i, j, pos, cb_pos;





 /* decode first LSF */

 pos = 0;
 cb_pos = 0;
 for (i = 0; i < LSF_NSPLIT; i++) {
 for (j = 0; j < dim_lsfCbTbl[i]; j++) {
 lsfdeq[pos + j] = lsfCbTbl[cb_pos +
 (long)(index[i])*dim_lsfCbTbl[i] + j];
 }
 pos += dim_lsfCbTbl[i];
 cb_pos += size_lsfCbTbl[i]*dim_lsfCbTbl[i];
 }

 if (lpc_n>1) {

 /* decode last LSF */

 pos = 0;
 cb_pos = 0;
 for (i = 0; i < LSF_NSPLIT; i++) {
 for (j = 0; j < dim_lsfCbTbl[i]; j++) {
 lsfdeq[LPC_FILTERORDER + pos + j] =
 lsfCbTbl[cb_pos +
 (long)(index[LSF_NSPLIT + i])*
 dim_lsfCbTbl[i] + j];
 }
 pos += dim_lsfCbTbl[i];
 cb_pos += size_lsfCbTbl[i]*dim_lsfCbTbl[i];
 }
 }
 }

 /*----------------------------------------------------------------*
 * obtain synthesis and weighting filters form lsf coefficients
 *---------------------------------------------------------------*/

 void DecoderInterpolateLSF(
 float *syntdenum, /* (o) synthesis filter coefficients */
 float *weightdenum, /* (o) weighting denumerator
 coefficients */
 float *lsfdeq, /* (i) dequantized lsf coefficients */
 int length, /* (i) length of lsf coefficient vector */
 iLBC_Dec_Inst_t *iLBCdec_inst
 /* (i) the decoder state structure */
 ){
 int i, pos, lp_length;
 float lp[LPC_FILTERORDER + 1], *lsfdeq2;






 lsfdeq2 = lsfdeq + length;
 lp_length = length + 1;

 if (iLBCdec_inst->mode==30) {
 /* sub-frame 1: Interpolation between old and first */

 LSFinterpolate2a_dec(lp, iLBCdec_inst->lsfdeqold, lsfdeq,
 lsf_weightTbl_30ms[0], length);
 memcpy(syntdenum,lp,lp_length*sizeof(float));
 bwexpand(weightdenum, lp, LPC_CHIRP_WEIGHTDENUM,
 lp_length);

 /* sub-frames 2 to 6: interpolation between first
 and last LSF */

 pos = lp_length;
 for (i = 1; i < 6; i++) {
 LSFinterpolate2a_dec(lp, lsfdeq, lsfdeq2,
 lsf_weightTbl_30ms[i], length);
 memcpy(syntdenum + pos,lp,lp_length*sizeof(float));
 bwexpand(weightdenum + pos, lp,
 LPC_CHIRP_WEIGHTDENUM, lp_length);
 pos += lp_length;
 }
 }
 else {
 pos = 0;
 for (i = 0; i < iLBCdec_inst->nsub; i++) {
 LSFinterpolate2a_dec(lp, iLBCdec_inst->lsfdeqold,
 lsfdeq, lsf_weightTbl_20ms[i], length);
 memcpy(syntdenum+pos,lp,lp_length*sizeof(float));
 bwexpand(weightdenum+pos, lp, LPC_CHIRP_WEIGHTDENUM,
 lp_length);
 pos += lp_length;
 }
 }

 /* update memory */

 if (iLBCdec_inst->mode==30)
 memcpy(iLBCdec_inst->lsfdeqold, lsfdeq2,
 length*sizeof(float));
 else
 memcpy(iLBCdec_inst->lsfdeqold, lsfdeq,
 length*sizeof(float));

 }