asterisk/codecs/ilbc/LPCdecode.c

153 lines
4.7 KiB
C

/******************************************************************
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));
}