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code.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.
 */

/* $Header: /tmp_amd/presto/export/kbs/jutta/src/gsm/RCS/code.c,v 1.3 1996/07/02 09:59:05 jutta Exp $ */

#include    "config.h"


#ifdef      HAS_STDLIB_H
#include    <stdlib.h>
#else
#     include "proto.h"
      extern char * memcpy P((char *, char *, int));
#endif

#include    "private.h"
#include    "gsm.h"
#include    "proto.h"

/* 
 *  4.2 FIXED POINT IMPLEMENTATION OF THE RPE-LTP CODER 
 */

void Gsm_Coder P8((S,s,LARc,Nc,bc,Mc,xmaxc,xMc),

      struct gsm_state  * S,

      word  * s,  /* [0..159] samples                 IN    */

/*
 * The RPE-LTD coder works on a frame by frame basis.  The length of
 * the frame is equal to 160 samples.  Some computations are done
 * once per frame to produce at the output of the coder the
 * LARc[1..8] parameters which are the coded LAR coefficients and 
 * also to realize the inverse filtering operation for the entire
 * frame (160 samples of signal d[0..159]).  These parts produce at
 * the output of the coder:
 */

      word  * LARc,     /* [0..7] LAR coefficients          OUT   */

/*
 * Procedure 4.2.11 to 4.2.18 are to be executed four times per
 * frame.  That means once for each sub-segment RPE-LTP analysis of
 * 40 samples.  These parts produce at the output of the coder:
 */

      word  * Nc, /* [0..3] LTP lag             OUT   */
      word  * bc, /* [0..3] coded LTP gain            OUT   */
      word  * Mc, /* [0..3] RPE grid selection        OUT     */
      word  * xmaxc,/* [0..3] Coded maximum amplitude OUT   */
      word  * xMc /* [13*4] normalized RPE samples    OUT   */
)
{
      int   k;
      word  * dp  = S->dp0 + 120;   /* [ -120...-1 ] */
      word  * dpp = dp;       /* [ 0...39 ]      */

      word  so[160];

      Gsm_Preprocess                (S, s, so);
      Gsm_LPC_Analysis        (S, so, LARc);
      Gsm_Short_Term_Analysis_Filter      (S, LARc, so);

      for (k = 0; k <= 3; k++, xMc += 13) {

            Gsm_Long_Term_Predictor ( S,
                               so+k*40, /* d      [0..39] IN      */
                               dp,    /* dp  [-120..-1] IN  */
                              S->e + 5, /* e      [0..39] OUT     */
                              dpp,    /* dpp    [0..39] OUT */
                               Nc++,
                               bc++);

            Gsm_RPE_Encoding  ( S,
                              S->e + 5,/* e       ][0..39][ IN/OUT */
                                xmaxc++, Mc++, xMc );
            /*
             * Gsm_Update_of_reconstructed_short_time_residual_signal
             *                ( dpp, S->e + 5, dp );
             */

            { register int i;
              register longword ltmp;
              for (i = 0; i <= 39; i++)
                  dp[ i ] = GSM_ADD( S->e[5 + i], dpp[i] );
            }
            dp  += 40;
            dpp += 40;

      }
      (void)memcpy( (char *)S->dp0, (char *)(S->dp0 + 160),
            120 * sizeof(*S->dp0) );
}

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