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.
13 #include "gsm610_priv.h"
17 * 4.2 FIXED POINT IMPLEMENTATION OF THE RPE-LTP CODER
22 struct gsm_state * State,
24 word * s, /* [0..159] samples IN */
27 * The RPE-LTD coder works on a frame by frame basis. The length of
28 * the frame is equal to 160 samples. Some computations are done
29 * once per frame to produce at the output of the coder the
30 * LARc[1..8] parameters which are the coded LAR coefficients and
31 * also to realize the inverse filtering operation for the entire
32 * frame (160 samples of signal d[0..159]). These parts produce at
33 * the output of the coder:
36 word * LARc, /* [0..7] LAR coefficients OUT */
39 * Procedure 4.2.11 to 4.2.18 are to be executed four times per
40 * frame. That means once for each sub-segment RPE-LTP analysis of
41 * 40 samples. These parts produce at the output of the coder:
44 word * Nc, /* [0..3] LTP lag OUT */
45 word * bc, /* [0..3] coded LTP gain OUT */
46 word * Mc, /* [0..3] RPE grid selection OUT */
47 word * xmaxc,/* [0..3] Coded maximum amplitude OUT */
48 word * xMc /* [13*4] normalized RPE samples OUT */
52 word * dp = State->dp0 + 120; /* [ -120...-1 ] */
53 word * dpp = dp; /* [ 0...39 ] */
57 Gsm_Preprocess (State, s, so);
58 Gsm_LPC_Analysis (State, so, LARc);
59 Gsm_Short_Term_Analysis_Filter (State, LARc, so);
61 for (k = 0; k <= 3; k++, xMc += 13) {
63 Gsm_Long_Term_Predictor ( State,
64 so+k*40, /* d [0..39] IN */
65 dp, /* dp [-120..-1] IN */
66 State->e + 5, /* e [0..39] OUT */
67 dpp, /* dpp [0..39] OUT */
71 Gsm_RPE_Encoding ( /*-S,-*/
72 State->e + 5, /* e ][0..39][ IN/OUT */
75 * Gsm_Update_of_reconstructed_short_time_residual_signal
80 for (i = 0; i <= 39; i++)
81 dp[ i ] = GSM_ADD( State->e[5 + i], dpp[i] );
87 (void)memcpy( (char *)State->dp0, (char *)(State->dp0 + 160),
88 120 * sizeof(*State->dp0) );
91 ** Do not edit or modify anything in this comment block.
92 ** The arch-tag line is a file identity tag for the GNU Arch
93 ** revision control system.
95 ** arch-tag: ae8ef1b2-5a1e-4263-94cd-42b15dca81a3