code.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        "config.h"

#ifdef  HAS_STRING_H
#include        <string.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 ]    */

        static word e[50];

        word    so[160];

#if !(defined(__GNUC__) && defined(__i386__))
        longword ltmp;
#endif

        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  */
                                        e + 5,    /* e      [0..39] OUT */
                                        dpp,      /* dpp    [0..39] OUT */
                                         Nc++,
                                         bc++);

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

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

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

---