interpretor/libsndfile-1.0.25/src/GSM610/decode.c

   1 /*
   2  * Copyright 1992 by Jutta Degener and Carsten Bormann, Technische
   3  * Universitaet Berlin.  See the accompanying file "COPYRIGHT" for
   4  * details.  THERE IS ABSOLUTELY NO WARRANTY FOR THIS SOFTWARE.
   5  */
   6
   7 #include <stdio.h>
   8
   9 #include        "gsm610_priv.h"
  10
  11 /*
  12  *  4.3 FIXED POINT IMPLEMENTATION OF THE RPE-LTP DECODER
  13  */
  14
  15 static void Postprocessing (
  16         struct gsm_state        * S,
  17         register word           * s)
  18 {
  19         register int            k;
  20         register word           msr = S->msr;
  21         register word           tmp;
  22
  23         for (k = 160; k--; s++) {
  24                 tmp = GSM_MULT_R( msr, 28180 );
  25                 msr = GSM_ADD(*s, tmp);            /* Deemphasis             */
  26                 *s  = GSM_ADD(msr, msr) & 0xFFF8;  /* Truncation & Upscaling */
  27         }
  28         S->msr = msr;
  29 }
  30
  31 void Gsm_Decoder (
  32         struct gsm_state        * S,
  33
  34         word            * LARcr,        /* [0..7]               IN      */
  35
  36         word            * Ncr,          /* [0..3]               IN      */
  37         word            * bcr,          /* [0..3]               IN      */
  38         word            * Mcr,          /* [0..3]               IN      */
  39         word            * xmaxcr,       /* [0..3]               IN      */
  40         word            * xMcr,         /* [0..13*4]            IN      */
  41
  42         word            * s)            /* [0..159]             OUT     */
  43 {
  44         int             j, k;
  45         word            erp[40], wt[160];
  46         word            * drp = S->dp0 + 120;
  47
  48         for (j=0; j <= 3; j++, xmaxcr++, bcr++, Ncr++, Mcr++, xMcr += 13) {
  49
  50                 Gsm_RPE_Decoding( /*-S,-*/ *xmaxcr, *Mcr, xMcr, erp );
  51                 Gsm_Long_Term_Synthesis_Filtering( S, *Ncr, *bcr, erp, drp );
  52
  53                 for (k = 0; k <= 39; k++) wt[ j * 40 + k ] =  drp[ k ];
  54         }
  55
  56         Gsm_Short_Term_Synthesis_Filter( S, LARcr, wt, s );
  57         Postprocessing(S, s);
  58 }
  59