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 /* $Header: /tmp_amd/presto/export/kbs/jutta/src/gsm/RCS/code.c,v 1.3 1996/07/02 09:59:05 jutta Exp $ */ 8 9 #include "config.h" 10 11 12 #ifdef HAS_STRING_H 13 #include <string.h> 14 #else 15 # include "proto.h" 16 extern char * memcpy P((char *, char *, int)); 17 #endif 18 19 #include "private.h" 20 #include "gsm.h" 21 #include "proto.h" 22 23 /* 24 * 4.2 FIXED POINT IMPLEMENTATION OF THE RPE-LTP CODER 25 */ 26 27 void Gsm_Coder P8((S,s,LARc,Nc,bc,Mc,xmaxc,xMc), 28 29 struct gsm_state * S, 30 31 word * s, /* [0..159] samples IN */ 32 33 /* 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: 41 */ 42 43 word * LARc, /* [0..7] LAR coefficients OUT */ 44 45 /* 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: 49 */ 50 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 */ 56 ) 57 { 58 int k; 59 word * dp = S->dp0 + 120; /* [ -120...-1 ] */ 60 word * dpp = dp; /* [ 0...39 ] */ 61 62 word so[160]; 63 64 Gsm_Preprocess (S, s, so); 65 Gsm_LPC_Analysis (S, so, LARc); 66 Gsm_Short_Term_Analysis_Filter (S, LARc, so); 67 68 for (k = 0; k <= 3; k++, xMc += 13) { 69 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 */ 75 Nc++, 76 bc++); 77 78 Gsm_RPE_Encoding ( S, 79 S->e + 5,/* e ][0..39][ IN/OUT */ 80 xmaxc++, Mc++, xMc ); 81 /* 82 * Gsm_Update_of_reconstructed_short_time_residual_signal 83 * ( dpp, S->e + 5, dp ); 84 */ 85 86 { register int i; 87 register longword ltmp; 88 for (i = 0; i <= 39; i++) 89 dp[ i ] = GSM_ADD( S->e[5 + i], dpp[i] ); 90 } 91 dp += 40; 92 dpp += 40; 93 94 } 95 (void)memcpy( (char *)S->dp0, (char *)(S->dp0 + 160), 96 120 * sizeof(*S->dp0) ); 97 } 98
