ref: 2515cb2de68b10eff93b876159dcbf180474f146
dir: /src/libgsm/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.
*/
#include <stdlib.h>
#include <string.h>
#include "private.h"
#include "gsm.h"
/*
* 4.2 FIXED POINT IMPLEMENTATION OF THE RPE-LTP CODER
*/
void Gsm_Coder (
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];
Gsm_Preprocess (S, s, so);
Gsm_LPC_Analysis (so, LARc);
Gsm_Short_Term_Analysis_Filter (S, LARc, so);
for (k = 0; k <= 3; k++, xMc += 13) {
Gsm_Long_Term_Predictor (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 ( 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;
register longword ltmp;
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) );
}