/project/jni/sndfile/src/GSM610/code.c

 1/*
 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.
 5 */
 6
 7
 8#include	<stdlib.h>
 9#include	<string.h>
10
11#include	"gsm610_priv.h"
12
13/* 
14 *  4.2 FIXED POINT IMPLEMENTATION OF THE RPE-LTP CODER 
15 */
16
17void Gsm_Coder (
18
19	struct gsm_state	* State,
20
21	word	* s,	/* [0..159] samples		  	IN	*/
22
23/*
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:
31 */
32
33	word	* LARc,	/* [0..7] LAR coefficients		OUT	*/
34
35/*
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:
39 */
40
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	*/
46)
47{
48	int	k;
49	word	* dp  = State->dp0 + 120;	/* [ -120...-1 ] */
50	word	* dpp = dp;		/* [ 0...39 ]	 */
51
52	word	so[160];
53
54	Gsm_Preprocess			(State, s, so);
55	Gsm_LPC_Analysis		(State, so, LARc);
56	Gsm_Short_Term_Analysis_Filter	(State, LARc, so);
57
58	for (k = 0; k <= 3; k++, xMc += 13) {
59
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 */
65					 Nc++,
66					 bc++);
67
68		Gsm_RPE_Encoding	( /*-S,-*/
69					State->e + 5,	/* e	  ][0..39][ IN/OUT */
70					  xmaxc++, Mc++, xMc );
71		/*
72		 * Gsm_Update_of_reconstructed_short_time_residual_signal
73		 *			( dpp, State->e + 5, dp );
74		 */
75
76		{ register int i;
77		  for (i = 0; i <= 39; i++)
78			dp[ i ] = GSM_ADD( State->e[5 + i], dpp[i] );
79		}
80		dp  += 40;
81		dpp += 40;
82
83	}
84	(void)memcpy( (char *)State->dp0, (char *)(State->dp0 + 160),
85		120 * sizeof(*State->dp0) );
86}
87