Mercurial > hg > audiostuff
comparison spandsp-0.0.3/spandsp-0.0.3/src/gsm0610_preprocess.c @ 5:f762bf195c4b
import spandsp-0.0.3
| author | Peter Meerwald <pmeerw@cosy.sbg.ac.at> |
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| date | Fri, 25 Jun 2010 16:00:21 +0200 |
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| 4:26cd8f1ef0b1 | 5:f762bf195c4b |
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| 1 /* | |
| 2 * SpanDSP - a series of DSP components for telephony | |
| 3 * | |
| 4 * gsm0610_preprocess.c - GSM 06.10 full rate speech codec. | |
| 5 * | |
| 6 * Written by Steve Underwood <steveu@coppice.org> | |
| 7 * | |
| 8 * Copyright (C) 2006 Steve Underwood | |
| 9 * | |
| 10 * All rights reserved. | |
| 11 * | |
| 12 * This program is free software; you can redistribute it and/or modify | |
| 13 * it under the terms of the GNU General Public License version 2, as | |
| 14 * published by the Free Software Foundation. | |
| 15 * | |
| 16 * This program is distributed in the hope that it will be useful, | |
| 17 * but WITHOUT ANY WARRANTY; without even the implied warranty of | |
| 18 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the | |
| 19 * GNU General Public License for more details. | |
| 20 * | |
| 21 * You should have received a copy of the GNU General Public License | |
| 22 * along with this program; if not, write to the Free Software | |
| 23 * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA. | |
| 24 * | |
| 25 * This code is based on the widely used GSM 06.10 code available from | |
| 26 * http://kbs.cs.tu-berlin.de/~jutta/toast.html | |
| 27 * | |
| 28 * $Id: gsm0610_preprocess.c,v 1.7 2006/11/19 14:07:24 steveu Exp $ | |
| 29 */ | |
| 30 | |
| 31 /*! \file */ | |
| 32 | |
| 33 #ifdef HAVE_CONFIG_H | |
| 34 #include <config.h> | |
| 35 #endif | |
| 36 | |
| 37 #include <assert.h> | |
| 38 #include <inttypes.h> | |
| 39 #if defined(HAVE_TGMATH_H) | |
| 40 #include <tgmath.h> | |
| 41 #endif | |
| 42 #if defined(HAVE_MATH_H) | |
| 43 #include <math.h> | |
| 44 #endif | |
| 45 #include <stdlib.h> | |
| 46 | |
| 47 #include "spandsp/telephony.h" | |
| 48 #include "spandsp/dc_restore.h" | |
| 49 #include "spandsp/gsm0610.h" | |
| 50 | |
| 51 #include "gsm0610_local.h" | |
| 52 | |
| 53 /* | |
| 54 4.2.0 .. 4.2.3 PREPROCESSING SECTION | |
| 55 | |
| 56 After A-law to linear conversion (or directly from the | |
| 57 A to D converter) the following scaling is assumed for | |
| 58 input to the RPE-LTP algorithm: | |
| 59 | |
| 60 in: 0.1.....................12 | |
| 61 S.v.v.v.v.v.v.v.v.v.v.v.v.*.*.* | |
| 62 | |
| 63 Where S is the sign bit, v a valid bit, and * a "don't care" bit. | |
| 64 The original signal is called sop[..] | |
| 65 | |
| 66 out: 0.1................... 12 | |
| 67 S.S.v.v.v.v.v.v.v.v.v.v.v.v.0.0 | |
| 68 */ | |
| 69 | |
| 70 void gsm0610_preprocess(gsm0610_state_t *s, const int16_t amp[GSM0610_FRAME_LEN], int16_t so[GSM0610_FRAME_LEN]) | |
| 71 { | |
| 72 int16_t z1; | |
| 73 int16_t mp; | |
| 74 int16_t s1; | |
| 75 int16_t msp; | |
| 76 int16_t SO; | |
| 77 int32_t L_z2; | |
| 78 int32_t L_s2; | |
| 79 int32_t L_temp; | |
| 80 #if !defined(__GNUC__) | |
| 81 int16_t lsp; | |
| 82 #endif | |
| 83 int k; | |
| 84 | |
| 85 z1 = s->z1; | |
| 86 L_z2 = s->L_z2; | |
| 87 mp = s->mp; | |
| 88 for (k = 0; k < GSM0610_FRAME_LEN; k++) | |
| 89 { | |
| 90 /* 4.2.1 Downscaling of the input signal */ | |
| 91 SO = (amp[k] >> 1) & ~3; | |
| 92 | |
| 93 assert(SO >= -0x4000); // downscaled by | |
| 94 assert(SO <= 0x3FFC); // previous routine. | |
| 95 | |
| 96 /* 4.2.2 Offset compensation */ | |
| 97 | |
| 98 /* This part implements a high-pass filter and requires extended | |
| 99 arithmetic precision for the recursive part of this filter. | |
| 100 The input of this procedure is the array so[0...159] and the | |
| 101 output the array sof[ 0...159 ]. | |
| 102 */ | |
| 103 /* Compute the non-recursive part */ | |
| 104 s1 = SO - z1; | |
| 105 z1 = SO; | |
| 106 | |
| 107 assert(s1 != INT16_MIN); | |
| 108 | |
| 109 /* Compute the recursive part */ | |
| 110 L_s2 = s1; | |
| 111 L_s2 <<= 15; | |
| 112 | |
| 113 /* Perform a 31 by 16 bits multiplication */ | |
| 114 #if defined(__GNUC__) | |
| 115 L_z2 = ((int64_t) L_z2*32735 + 0x4000) >> 15; | |
| 116 /* Alternate (ANSI) version of below line does slightly different rounding: | |
| 117 * L_temp = L_z2 >> 9; | |
| 118 * L_temp += L_temp >> 5; | |
| 119 * L_temp = (++L_temp) >> 1; | |
| 120 * L_z2 = L_z2 - L_temp; | |
| 121 */ | |
| 122 L_z2 = gsm_l_add(L_z2, L_s2); | |
| 123 #else | |
| 124 /* This does L_z2 = L_z2 * 0x7FD5/0x8000 + L_s2 */ | |
| 125 msp = (int16_t) (L_z2 >> 15); | |
| 126 lsp = (int16_t) (L_z2 - ((int32_t) msp << 15)); | |
| 127 | |
| 128 L_s2 += gsm_mult_r(lsp, 32735); | |
| 129 L_temp = (int32_t) msp*32735; | |
| 130 L_z2 = gsm_l_add(L_temp, L_s2); | |
| 131 #endif | |
| 132 | |
| 133 /* Compute sof[k] with rounding */ | |
| 134 L_temp = gsm_l_add(L_z2, 16384); | |
| 135 | |
| 136 /* 4.2.3 Preemphasis */ | |
| 137 msp = gsm_mult_r(mp, -28180); | |
| 138 mp = (int16_t) (L_temp >> 15); | |
| 139 so[k] = gsm_add(mp, msp); | |
| 140 } | |
| 141 /*endfor*/ | |
| 142 | |
| 143 s->z1 = z1; | |
| 144 s->L_z2 = L_z2; | |
| 145 s->mp = mp; | |
| 146 } | |
| 147 /*- End of function --------------------------------------------------------*/ | |
| 148 /*- End of file ------------------------------------------------------------*/ |