Mercurial > hg > audiostuff
comparison intercom/gsm/preproce.c @ 2:13be24d74cd2
import intercom-0.4.1
| author | Peter Meerwald <pmeerw@cosy.sbg.ac.at> |
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| date | Fri, 25 Jun 2010 09:57:52 +0200 |
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| 1:9cadc470e3da | 2:13be24d74cd2 |
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| 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: /home/kbs/jutta/src/gsm/gsm-1.0/src/RCS/preprocess.c,v 1.1 1992/10/28 00:15:50 jutta Exp $ */ | |
| 8 | |
| 9 #include <stdio.h> | |
| 10 #include <assert.h> | |
| 11 | |
| 12 #include "private.h" | |
| 13 | |
| 14 #include "gsm.h" | |
| 15 #include "proto.h" | |
| 16 | |
| 17 /* 4.2.0 .. 4.2.3 PREPROCESSING SECTION | |
| 18 * | |
| 19 * After A-law to linear conversion (or directly from the | |
| 20 * Ato D converter) the following scaling is assumed for | |
| 21 * input to the RPE-LTP algorithm: | |
| 22 * | |
| 23 * in: 0.1.....................12 | |
| 24 * S.v.v.v.v.v.v.v.v.v.v.v.v.*.*.* | |
| 25 * | |
| 26 * Where S is the sign bit, v a valid bit, and * a "don't care" bit. | |
| 27 * The original signal is called sop[..] | |
| 28 * | |
| 29 * out: 0.1................... 12 | |
| 30 * S.S.v.v.v.v.v.v.v.v.v.v.v.v.0.0 | |
| 31 */ | |
| 32 | |
| 33 | |
| 34 void Gsm_Preprocess P3((S, s, so), | |
| 35 struct gsm_state *S, word * s, word * so) | |
| 36 { /* [0..159] IN/OUT */ | |
| 37 | |
| 38 word z1 = S->z1; | |
| 39 longword L_z2 = S->L_z2; | |
| 40 word mp = S->mp; | |
| 41 | |
| 42 word s1; | |
| 43 longword L_s2; | |
| 44 | |
| 45 longword L_temp; | |
| 46 | |
| 47 word msp, lsp; | |
| 48 word SO; | |
| 49 | |
| 50 longword ltmp; /* for ADD */ | |
| 51 ulongword utmp; /* for L_ADD */ | |
| 52 | |
| 53 register int k = 160; | |
| 54 | |
| 55 while (k--) { | |
| 56 | |
| 57 /* 4.2.1 Downscaling of the input signal | |
| 58 */ | |
| 59 SO = SASR(*s, 3) << 2; | |
| 60 s++; | |
| 61 | |
| 62 assert(SO >= -0x4000); /* downscaled by */ | |
| 63 assert(SO <= 0x3FFC); /* previous routine. */ | |
| 64 | |
| 65 | |
| 66 /* 4.2.2 Offset compensation | |
| 67 * | |
| 68 * This part implements a high-pass filter and requires extended | |
| 69 * arithmetic precision for the recursive part of this filter. | |
| 70 * The input of this procedure is the array so[0...159] and the | |
| 71 * output the array sof[ 0...159 ]. | |
| 72 */ | |
| 73 /* Compute the non-recursive part | |
| 74 */ | |
| 75 | |
| 76 s1 = SO - z1; /* s1 = gsm_sub( *so, z1 ); */ | |
| 77 z1 = SO; | |
| 78 | |
| 79 assert(s1 != MIN_WORD); | |
| 80 | |
| 81 /* Compute the recursive part | |
| 82 */ | |
| 83 L_s2 = s1; | |
| 84 L_s2 <<= 15; | |
| 85 | |
| 86 /* Execution of a 31 bv 16 bits multiplication | |
| 87 */ | |
| 88 | |
| 89 msp = SASR(L_z2, 15); | |
| 90 lsp = L_z2 - ((longword) msp << 15); /* gsm_L_sub(L_z2,(msp<<15)); */ | |
| 91 | |
| 92 L_s2 += GSM_MULT_R(lsp, 32735); | |
| 93 L_temp = (longword) msp *32735; /* GSM_L_MULT(msp,32735) >> 1; */ | |
| 94 L_z2 = GSM_L_ADD(L_temp, L_s2); | |
| 95 | |
| 96 /* Compute sof[k] with rounding | |
| 97 */ | |
| 98 L_temp = GSM_L_ADD(L_z2, 16384); | |
| 99 | |
| 100 /* 4.2.3 Preemphasis | |
| 101 */ | |
| 102 | |
| 103 msp = GSM_MULT_R(mp, -28180); | |
| 104 mp = SASR(L_temp, 15); | |
| 105 *so++ = GSM_ADD(mp, msp); | |
| 106 } | |
| 107 | |
| 108 S->z1 = z1; | |
| 109 S->L_z2 = L_z2; | |
| 110 S->mp = mp; | |
| 111 } |