gsm/src/decode.c

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/*
 * 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.
 */
 
/* $Header$ */
 
#include <stdio.h>
 
#include    "private.h"
#include    "gsm.h"
#include    "proto.h"
 
/*
 *  4.3 FIXED POINT IMPLEMENTATION OF THE RPE-LTP DECODER
 */
 
static void Postprocessing P2((S,s),
    struct gsm_state    * S,
    register word       * s)
{
    register int        k;
    register word       msr = S->msr;
    register word       tmp;
 
    for (k = 160; k--; s++) {
        tmp = (word)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 P8((S,LARcr, Ncr,bcr,Mcr,xmaxcr,xMcr,s),
    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( S, *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);
}