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 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 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);
}

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