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);
}