ref: 2515cb2de68b10eff93b876159dcbf180474f146
dir: /src/libgsm/decode.c/
/*
* Copyright 1992 by Jutta Degener and Carsten Bormann, Technische
* Universitaet Berlin. See the accompanying file "COPYRIGHT" for
* details. THERE IS ABSOLUTELY NO WARRANTY FOR THIS SOFTWARE.
*/
#include <stdio.h>
#include "private.h"
#include "gsm.h"
/*
* 4.3 FIXED POINT IMPLEMENTATION OF THE RPE-LTP DECODER
*/
static void Postprocessing (
struct gsm_state * S,
register word * s)
{
register int k;
register word msr = S->msr;
register longword ltmp; /* for GSM_ADD */
register word tmp;
for (k = 160; k--; s++) {
tmp = GSM_MULT_R( msr, 28180 );
msr = GSM_ADD(*s, tmp); /* Deemphasis */
*s = GSM_ADD(msr, msr) & 0xFFF8; /* Truncation & Upscaling */
}
S->msr = msr;
}
void Gsm_Decoder (
struct gsm_state * S,
word * LARcr, /* [0..7] IN */
word * Ncr, /* [0..3] IN */
word * bcr, /* [0..3] IN */
word * Mcr, /* [0..3] IN */
word * xmaxcr, /* [0..3] IN */
word * xMcr, /* [0..13*4] IN */
word * s) /* [0..159] OUT */
{
int j, k;
word erp[40], wt[160];
word * drp = S->dp0 + 120;
for (j=0; j <= 3; j++, xmaxcr++, bcr++, Ncr++, Mcr++, xMcr += 13) {
Gsm_RPE_Decoding( *xmaxcr, *Mcr, xMcr, erp );
Gsm_Long_Term_Synthesis_Filtering( S, *Ncr, *bcr, erp, drp );
for (k = 0; k <= 39; k++) wt[ j * 40 + k ] = drp[ k ];
}
Gsm_Short_Term_Synthesis_Filter( S, LARcr, wt, s );
Postprocessing(S, s);
}