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5
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1 /*
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2 * SpanDSP - a series of DSP components for telephony
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3 *
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4 * ima_adpcm.c - Conversion routines between linear 16 bit PCM data and
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5 * IMA/DVI/Intel ADPCM format.
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6 *
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7 * Written by Steve Underwood <steveu@coppice.org>
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8 *
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9 * Copyright (C) 2001, 2004 Steve Underwood
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10 *
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11 * All rights reserved.
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12 *
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13 * This program is free software; you can redistribute it and/or modify
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14 * it under the terms of the GNU General Public License version 2, as
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15 * published by the Free Software Foundation.
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16 *
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17 * This program is distributed in the hope that it will be useful,
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18 * but WITHOUT ANY WARRANTY; without even the implied warranty of
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19 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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20 * GNU General Public License for more details.
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21 *
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22 * You should have received a copy of the GNU General Public License
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23 * along with this program; if not, write to the Free Software
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24 * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
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25 *
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26 * $Id: ima_adpcm.c,v 1.18 2006/11/30 15:41:47 steveu Exp $
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27 */
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28
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29 /*! \file */
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30
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31 #ifdef HAVE_CONFIG_H
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32 #include <config.h>
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33 #endif
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34
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35 #include <stdlib.h>
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36 #include <inttypes.h>
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37 #include <string.h>
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38 #if defined(HAVE_TGMATH_H)
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39 #include <tgmath.h>
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40 #endif
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41 #if defined(HAVE_MATH_H)
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42 #include <math.h>
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43 #endif
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44
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45 #include "spandsp/telephony.h"
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46 #include "spandsp/dc_restore.h"
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47 #include "spandsp/ima_adpcm.h"
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48
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49 /*
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50 * Intel/DVI ADPCM coder/decoder.
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51 *
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52 * The algorithm for this coder was taken from the IMA Compatability Project
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53 * proceedings, Vol 2, Number 2; May 1992.
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54 *
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55 * The RTP payload specs. reference a variant of DVI, called VDVI. This attempts to
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56 * further compresses, in a variable bit rate manner, by expressing the 4 bit codes
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57 * from the DVI codec as:
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58 *
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59 * 0 00
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60 * 1 010
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61 * 2 1100
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62 * 3 11100
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63 * 4 111100
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64 * 5 1111100
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65 * 6 11111100
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66 * 7 11111110
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67 * 8 10
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68 * 9 011
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69 * 10 1101
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70 * 11 11101
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71 * 12 111101
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72 * 13 1111101
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73 * 14 11111101
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74 * 15 11111111
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75 *
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76 * Any left over bits in the last octet of an encoded burst are set to one.
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77 */
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78
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79 /* Intel ADPCM step variation table */
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80 static const int step_size[89] =
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81 {
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82 7, 8, 9, 10, 11, 12, 13, 14, 16, 17,
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83 19, 21, 23, 25, 28, 31, 34, 37, 41, 45,
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84 50, 55, 60, 66, 73, 80, 88, 97, 107, 118,
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85 130, 143, 157, 173, 190, 209, 230, 253, 279, 307,
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86 337, 371, 408, 449, 494, 544, 598, 658, 724, 796,
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87 876, 963, 1060, 1166, 1282, 1411, 1552, 1707, 1878, 2066,
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88 2272, 2499, 2749, 3024, 3327, 3660, 4026, 4428, 4871, 5358,
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89 5894, 6484, 7132, 7845, 8630, 9493, 10442, 11487, 12635, 13899,
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90 15289, 16818, 18500, 20350, 22385, 24623, 27086, 29794, 32767
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91 };
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92
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93 static const int step_adjustment[8] =
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94 {
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95 -1, -1, -1, -1, 2, 4, 6, 8
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96 };
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97
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98 static const struct
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99 {
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100 uint8_t code;
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101 uint8_t bits;
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102 } vdvi_encode[] =
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103 {
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104 {0x00, 2},
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105 {0x02, 3},
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106 {0x0C, 4},
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107 {0x1C, 5},
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108 {0x3C, 6},
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109 {0x7C, 7},
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110 {0xFC, 8},
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111 {0xFE, 8},
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112 {0x02, 2},
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113 {0x03, 3},
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114 {0x0D, 4},
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115 {0x1D, 5},
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116 {0x3D, 6},
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117 {0x7D, 7},
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118 {0xFD, 8},
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119 {0xFF, 8}
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120 };
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121
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122 static const struct
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123 {
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124 uint16_t code;
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125 uint16_t mask;
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126 uint8_t bits;
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127 } vdvi_decode[] =
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128 {
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129 {0x0000, 0xC000, 2},
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130 {0x4000, 0xE000, 3},
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131 {0xC000, 0xF000, 4},
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132 {0xE000, 0xF800, 5},
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133 {0xF000, 0xFC00, 6},
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134 {0xF800, 0xFE00, 7},
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135 {0xFC00, 0xFF00, 8},
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136 {0xFE00, 0xFF00, 8},
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137 {0x8000, 0xC000, 2},
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138 {0x6000, 0xE000, 3},
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139 {0xD000, 0xF000, 4},
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140 {0xE800, 0xF800, 5},
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141 {0xF400, 0xFC00, 6},
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142 {0xFA00, 0xFE00, 7},
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143 {0xFD00, 0xFF00, 8},
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144 {0xFF00, 0xFF00, 8}
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145 };
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146
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147 static int16_t decode(ima_adpcm_state_t *s, uint8_t adpcm)
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148 {
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149 int e;
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150 int ss;
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151 int16_t linear;
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152
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153 /* e = (adpcm+0.5)*step/4 */
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154
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155 ss = step_size[s->step_index];
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156 e = ss >> 3;
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157 if (adpcm & 0x01)
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158 e += (ss >> 2);
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159 /*endif*/
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160 if (adpcm & 0x02)
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161 e += (ss >> 1);
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162 /*endif*/
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163 if (adpcm & 0x04)
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164 e += ss;
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165 /*endif*/
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166 if (adpcm & 0x08)
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167 e = -e;
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168 /*endif*/
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169 linear = saturate(s->last + e);
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170 s->last = linear;
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171 s->step_index += step_adjustment[adpcm & 0x07];
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172 if (s->step_index < 0)
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173 s->step_index = 0;
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174 else if (s->step_index > 88)
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175 s->step_index = 88;
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176 /*endif*/
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177 return linear;
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178 }
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179 /*- End of function --------------------------------------------------------*/
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180
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181 static uint8_t encode(ima_adpcm_state_t *s, int16_t linear)
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182 {
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183 int e;
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184 int ss;
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185 int adpcm;
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186 int diff;
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187 int initial_e;
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188
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189 ss = step_size[s->step_index];
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190 initial_e =
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191 e = linear - s->last;
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192 diff = ss >> 3;
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193 adpcm = (uint8_t) 0x00;
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194 if (e < 0)
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195 {
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196 adpcm = (uint8_t) 0x08;
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197 e = -e;
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198 }
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199 /*endif*/
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200 if (e >= ss)
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201 {
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202 adpcm |= (uint8_t) 0x04;
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203 e -= ss;
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204 }
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205 /*endif*/
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206 ss >>= 1;
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207 if (e >= ss)
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208 {
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209 adpcm |= (uint8_t) 0x02;
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210 e -= ss;
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211 }
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212 /*endif*/
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213 ss >>= 1;
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214 if (e >= ss)
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215 {
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216 adpcm |= (uint8_t) 0x01;
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217 e -= ss;
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218 }
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219 /*endif*/
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220
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221 if (initial_e < 0)
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222 diff = -(diff - initial_e - e);
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223 else
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224 diff = diff + initial_e - e;
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225 /*endif*/
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226 s->last = saturate(diff + s->last);
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227 s->step_index += step_adjustment[adpcm & 0x07];
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228 if (s->step_index < 0)
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229 s->step_index = 0;
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230 else if (s->step_index > 88)
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231 s->step_index = 88;
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232 /*endif*/
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233 return (uint8_t) adpcm;
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234 }
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235 /*- End of function --------------------------------------------------------*/
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236
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237 ima_adpcm_state_t *ima_adpcm_init(ima_adpcm_state_t *s, int variant)
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238 {
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239 if (s == NULL)
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240 {
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241 if ((s = (ima_adpcm_state_t *) malloc(sizeof(*s))) == NULL)
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242 return NULL;
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243 }
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244 /*endif*/
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245 memset(s, 0, sizeof(*s));
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246 s->variant = variant;
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247 return s;
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248 }
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249 /*- End of function --------------------------------------------------------*/
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250
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251 int ima_adpcm_release(ima_adpcm_state_t *s)
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252 {
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253 free(s);
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254 return 0;
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255 }
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256 /*- End of function --------------------------------------------------------*/
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257
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258 int ima_adpcm_decode(ima_adpcm_state_t *s,
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259 int16_t amp[],
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260 const uint8_t ima_data[],
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261 int ima_bytes)
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262 {
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263 int i;
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264 int j;
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265 int samples;
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266 uint16_t code;
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267
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268 samples = 0;
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269 if (s->variant == IMA_ADPCM_VDVI)
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270 {
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271 code = 0;
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272 s->bits = 0;
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273 for (i = 0; ; )
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274 {
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275 if (s->bits <= 8)
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276 {
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277 if (i >= ima_bytes)
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278 break;
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279 /*endif*/
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280 code |= ((uint16_t) ima_data[i++] << (8 - s->bits));
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281 s->bits += 8;
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282 }
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283 /*endif*/
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284 for (j = 0; j < 8; j++)
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285 {
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286 if ((vdvi_decode[j].mask & code) == vdvi_decode[j].code)
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287 break;
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288 if ((vdvi_decode[j + 8].mask & code) == vdvi_decode[j + 8].code)
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289 {
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290 j += 8;
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291 break;
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292 }
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293 /*endif*/
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294 }
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295 /*endfor*/
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296 amp[samples++] = decode(s, (uint8_t) j);
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297 code <<= vdvi_decode[j].bits;
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298 s->bits -= vdvi_decode[j].bits;
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299 }
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300 /*endfor*/
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301 /* Use up the remanents of the last octet */
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302 while (s->bits > 0)
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303 {
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304 for (j = 0; j < 8; j++)
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305 {
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306 if ((vdvi_decode[j].mask & code) == vdvi_decode[j].code)
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307 break;
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308 /*endif*/
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309 if ((vdvi_decode[j + 8].mask & code) == vdvi_decode[j + 8].code)
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310 {
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311 j += 8;
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312 break;
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313 }
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314 /*endif*/
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315 }
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316 /*endfor*/
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317 if (vdvi_decode[j].bits > s->bits)
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318 break;
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319 /*endif*/
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320 amp[samples++] = decode(s, (uint8_t) j);
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321 code <<= vdvi_decode[j].bits;
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322 s->bits -= vdvi_decode[j].bits;
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323 }
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324 /*endfor*/
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325 }
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326 else
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327 {
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328 for (i = 0; i < ima_bytes; i++)
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329 {
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330 amp[samples++] = decode(s, ima_data[i] & 0xF);
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331 amp[samples++] = decode(s, (ima_data[i] >> 4) & 0xF);
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332 }
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333 /*endwhile*/
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334 }
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335 /*endif*/
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336 return samples;
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337 }
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338 /*- End of function --------------------------------------------------------*/
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339
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340 int ima_adpcm_encode(ima_adpcm_state_t *s,
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341 uint8_t ima_data[],
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342 const int16_t amp[],
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343 int len)
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344 {
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345 int i;
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346 int bytes;
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347 uint8_t code;
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348
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349 bytes = 0;
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350 if (s->variant == IMA_ADPCM_VDVI)
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351 {
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352 s->bits = 0;
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353 for (i = 0; i < len; i++)
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354 {
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355 code = encode(s, amp[i]);
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356 s->ima_byte = (s->ima_byte << vdvi_encode[code].bits) | vdvi_encode[code].code;
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357 s->bits += vdvi_encode[code].bits;
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358 if (s->bits >= 8)
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359 {
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360 s->bits -= 8;
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361 ima_data[bytes++] = (uint8_t) (s->ima_byte >> s->bits);
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362 }
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363 /*endif*/
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364 }
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365 /*endfor*/
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366 if (s->bits)
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367 {
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368 ima_data[bytes++] = (uint8_t) (((s->ima_byte << 8) | 0xFF) >> s->bits);
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369 }
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370 /*endif*/
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371 }
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372 else
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373 {
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374 for (i = 0; i < len; i++)
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375 {
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376 s->ima_byte = (uint8_t) ((s->ima_byte >> 4) | (encode(s, amp[i]) << 4));
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377 if ((s->bits++ & 1))
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378 ima_data[bytes++] = (uint8_t) s->ima_byte;
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379 /*endif*/
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380 }
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381 /*endfor*/
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382 }
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383 /*endif*/
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384 return bytes;
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385 }
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386 /*- End of function --------------------------------------------------------*/
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387 /*- End of file ------------------------------------------------------------*/
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