78cb853c1d79e0530103362c058779c8b4a727be
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.
11 #include "gsm610_priv.h"
14 * 4.2 FIXED POINT IMPLEMENTATION OF THE RPE-LTP CODER
19 struct gsm_state
* State
,
21 word
* s
, /* [0..159] samples IN */
24 * The RPE-LTD coder works on a frame by frame basis. The length of
25 * the frame is equal to 160 samples. Some computations are done
26 * once per frame to produce at the output of the coder the
27 * LARc[1..8] parameters which are the coded LAR coefficients and
28 * also to realize the inverse filtering operation for the entire
29 * frame (160 samples of signal d[0..159]). These parts produce at
30 * the output of the coder:
33 word
* LARc
, /* [0..7] LAR coefficients OUT */
36 * Procedure 4.2.11 to 4.2.18 are to be executed four times per
37 * frame. That means once for each sub-segment RPE-LTP analysis of
38 * 40 samples. These parts produce at the output of the coder:
41 word
* Nc
, /* [0..3] LTP lag OUT */
42 word
* bc
, /* [0..3] coded LTP gain OUT */
43 word
* Mc
, /* [0..3] RPE grid selection OUT */
44 word
* xmaxc
,/* [0..3] Coded maximum amplitude OUT */
45 word
* xMc
/* [13*4] normalized RPE samples OUT */
49 word
* dp
= State
->dp0
+ 120; /* [ -120...-1 ] */
50 word
* dpp
= dp
; /* [ 0...39 ] */
54 Gsm_Preprocess (State
, s
, so
);
55 Gsm_LPC_Analysis (State
, so
, LARc
);
56 Gsm_Short_Term_Analysis_Filter (State
, LARc
, so
);
58 for (k
= 0; k
<= 3; k
++, xMc
+= 13) {
60 Gsm_Long_Term_Predictor ( State
,
61 so
+k
*40, /* d [0..39] IN */
62 dp
, /* dp [-120..-1] IN */
63 State
->e
+ 5, /* e [0..39] OUT */
64 dpp
, /* dpp [0..39] OUT */
68 Gsm_RPE_Encoding ( /*-S,-*/
69 State
->e
+ 5, /* e ][0..39][ IN/OUT */
72 * Gsm_Update_of_reconstructed_short_time_residual_signal
73 * ( dpp, State->e + 5, dp );
77 for (i
= 0; i
<= 39; i
++)
78 dp
[ i
] = GSM_ADD( State
->e
[5 + i
], dpp
[i
] );
84 (void)memcpy( (char *)State
->dp0
, (char *)(State
->dp0
+ 160),
85 120 * sizeof(*State
->dp0
) );