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.
7
/* $Header: /tmp_amd/presto/export/kbs/jutta/src/gsm/RCS/code.c,v 1.3 1996/07/02 09:59:05 jutta Exp $ */
16
extern char * memcpy P((char *, char *, int));
24
* 4.2 FIXED POINT IMPLEMENTATION OF THE RPE-LTP CODER
27
void Gsm_Coder P8((S,s,LARc,Nc,bc,Mc,xmaxc,xMc),
31
word * s, /* [0..159] samples IN */
34
* The RPE-LTD coder works on a frame by frame basis. The length of
35
* the frame is equal to 160 samples. Some computations are done
36
* once per frame to produce at the output of the coder the
37
* LARc[1..8] parameters which are the coded LAR coefficients and
38
* also to realize the inverse filtering operation for the entire
39
* frame (160 samples of signal d[0..159]). These parts produce at
40
* the output of the coder:
43
word * LARc, /* [0..7] LAR coefficients OUT */
46
* Procedure 4.2.11 to 4.2.18 are to be executed four times per
47
* frame. That means once for each sub-segment RPE-LTP analysis of
48
* 40 samples. These parts produce at the output of the coder:
51
word * Nc, /* [0..3] LTP lag OUT */
52
word * bc, /* [0..3] coded LTP gain OUT */
53
word * Mc, /* [0..3] RPE grid selection OUT */
54
word * xmaxc,/* [0..3] Coded maximum amplitude OUT */
55
word * xMc /* [13*4] normalized RPE samples OUT */
59
word * dp = S->dp0 + 120; /* [ -120...-1 ] */
60
word * dpp = dp; /* [ 0...39 ] */
64
Gsm_Preprocess (S, s, so);
65
Gsm_LPC_Analysis (S, so, LARc);
66
Gsm_Short_Term_Analysis_Filter (S, LARc, so);
68
for (k = 0; k <= 3; k++, xMc += 13) {
70
Gsm_Long_Term_Predictor ( S,
71
so+k*40, /* d [0..39] IN */
72
dp, /* dp [-120..-1] IN */
73
S->e + 5, /* e [0..39] OUT */
74
dpp, /* dpp [0..39] OUT */
79
S->e + 5,/* e ][0..39][ IN/OUT */
82
* Gsm_Update_of_reconstructed_short_time_residual_signal
83
* ( dpp, S->e + 5, dp );
87
register longword ltmp;
88
for (i = 0; i <= 39; i++)
89
dp[ i ] = GSM_ADD( S->e[5 + i], dpp[i] );
95
(void)memcpy( (char *)S->dp0, (char *)(S->dp0 + 160),
96
120 * sizeof(*S->dp0) );