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.
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 ] */
66 Gsm_Preprocess (S, s, so);
67 Gsm_LPC_Analysis (S, so, LARc);
68 Gsm_Short_Term_Analysis_Filter (S, LARc, so);
70 for (k = 0; k <= 3; k++, xMc += 13) {
72 Gsm_Long_Term_Predictor ( S,
73 so+k*40, /* d [0..39] IN */
74 dp, /* dp [-120..-1] IN */
75 e + 5, /* e [0..39] OUT */
76 dpp, /* dpp [0..39] OUT */
81 e + 5, /* e ][0..39][ IN/OUT */
84 * Gsm_Update_of_reconstructed_short_time_residual_signal
89 register longword ltmp;
90 for (i = 0; i <= 39; i++)
91 dp[ i ] = GSM_ADD( e[5 + i], dpp[i] );
97 (void)memcpy( (char *)S->dp0, (char *)(S->dp0 + 160),
98 120 * sizeof(*S->dp0) );