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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 * oki_adpcm.c - Conversion routines between linear 16 bit PCM data and
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5 * OKI (Dialogic) ADPCM format. Supports with the 32kbps
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6 * and 24kbps variants used by Dialogic.
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7 *
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8 * Written by Steve Underwood <steveu@coppice.org>
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9 *
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10 * Copyright (C) 2001, 2004 Steve Underwood
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11 *
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12 * The actual OKI ADPCM encode and decode method is derived from freely
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13 * available code, whose exact origins seem uncertain.
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14 *
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15 * All rights reserved.
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16 *
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17 * This program is free software; you can redistribute it and/or modify
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18 * it under the terms of the GNU General Public License version 2, as
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19 * published by the Free Software Foundation.
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20 *
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21 * This program is distributed in the hope that it will be useful,
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22 * but WITHOUT ANY WARRANTY; without even the implied warranty of
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23 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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24 * GNU General Public License for more details.
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25 *
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26 * You should have received a copy of the GNU General Public License
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27 * along with this program; if not, write to the Free Software
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28 * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
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29 *
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30 * $Id: oki_adpcm.c,v 1.22 2006/11/28 16:59:56 steveu Exp $
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31 */
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32
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33 /*! \file */
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34
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35 #ifdef HAVE_CONFIG_H
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36 #include <config.h>
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37 #endif
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38
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39 #include <stdlib.h>
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40 #include <inttypes.h>
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41 #include <string.h>
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42
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43 #include "spandsp/telephony.h"
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44 #include "spandsp/oki_adpcm.h"
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45
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46 /* Routines to convert 12 bit linear samples to the Oki ADPCM coding format,
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47 widely used in CTI, because Dialogic use it. */
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48
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49 static const int16_t step_size[49] =
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50 {
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51 16, 17, 19, 21, 23, 25, 28, 31,
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52 34, 37, 41, 45, 50, 55, 60, 66,
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53 73, 80, 88, 97, 107, 118, 130, 143,
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54 157, 173, 190, 209, 230, 253, 279, 307,
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55 337, 371, 408, 449, 494, 544, 598, 658,
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56 724, 796, 876, 963, 1060, 1166, 1282, 1408,
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57 1552
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58 };
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59
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60 static const int16_t step_adjustment[8] =
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61 {
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62 -1, -1, -1, -1, 2, 4, 6, 8
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63 };
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64
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65 /* Band limiting filter, to allow sample rate conversion to and
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66 from 6k samples/second. */
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67 static const float cutoff_coeffs[] =
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68 {
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69 -3.648392e-4f,
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70 5.062391e-4f,
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71 1.206247e-3f,
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72 1.804452e-3f,
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73 1.691750e-3f,
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74 4.083405e-4f,
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75 -1.931085e-3f,
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76 -4.452107e-3f,
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77 -5.794821e-3f,
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78 -4.778489e-3f,
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79 -1.161266e-3f,
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80 3.928504e-3f,
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81 8.259786e-3f,
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82 9.500425e-3f,
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83 6.512800e-3f,
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84 2.227856e-4f,
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85 -6.531275e-3f,
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86 -1.026843e-2f,
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87 -8.718062e-3f,
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88 -2.280487e-3f,
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89 5.817733e-3f,
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90 1.096777e-2f,
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91 9.634404e-3f,
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92 1.569301e-3f,
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93 -9.522632e-3f,
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94 -1.748273e-2f,
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95 -1.684408e-2f,
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96 -6.100054e-3f,
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97 1.071206e-2f,
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98 2.525209e-2f,
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99 2.871779e-2f,
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100 1.664411e-2f,
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101 -7.706268e-3f,
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102 -3.331083e-2f,
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103 -4.521249e-2f,
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104 -3.085962e-2f,
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105 1.373653e-2f,
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106 8.089593e-2f,
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107 1.529060e-1f,
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108 2.080487e-1f,
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109 2.286834e-1f,
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110 2.080487e-1f,
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111 1.529060e-1f,
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112 8.089593e-2f,
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113 1.373653e-2f,
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114 -3.085962e-2f,
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115 -4.521249e-2f,
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116 -3.331083e-2f,
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117 -7.706268e-3f,
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118 1.664411e-2f,
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119 2.871779e-2f,
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120 2.525209e-2f,
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121 1.071206e-2f,
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122 -6.100054e-3f,
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123 -1.684408e-2f,
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124 -1.748273e-2f,
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125 -9.522632e-3f,
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126 1.569301e-3f,
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127 9.634404e-3f,
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128 1.096777e-2f,
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129 5.817733e-3f,
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130 -2.280487e-3f,
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131 -8.718062e-3f,
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132 -1.026843e-2f,
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133 -6.531275e-3f,
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134 2.227856e-4f,
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135 6.512800e-3f,
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136 9.500425e-3f,
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137 8.259786e-3f,
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138 3.928504e-3f,
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139 -1.161266e-3f,
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140 -4.778489e-3f,
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141 -5.794821e-3f,
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142 -4.452107e-3f,
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143 -1.931085e-3f,
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144 4.083405e-4f,
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145 1.691750e-3f,
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146 1.804452e-3f,
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147 1.206247e-3f,
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148 5.062391e-4f,
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149 -3.648392e-4f
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150 };
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151
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152 static int16_t decode(oki_adpcm_state_t *s, uint8_t adpcm)
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153 {
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154 int16_t e;
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155 int16_t ss;
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156 int16_t linear;
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157
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158 /* Doing the next part as follows:
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159 *
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160 * x = adpcm & 0x07;
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161 * e = (step_size[s->step_index]*(x + x + 1)) >> 3;
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162 *
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163 * Seems an obvious improvement on a modern machine, but remember
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164 * the truncation errors do not come out the same. It would
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165 * not, therefore, be an exact match for what this code is doing.
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166 *
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167 * Just what a Dialogic card does, I do not know!
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168 */
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169
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170 ss = step_size[s->step_index];
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171 e = ss >> 3;
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172 if (adpcm & 0x01)
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173 e += (ss >> 2);
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174 /*endif*/
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175 if (adpcm & 0x02)
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176 e += (ss >> 1);
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177 /*endif*/
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178 if (adpcm & 0x04)
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179 e += ss;
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180 /*endif*/
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181 if (adpcm & 0x08)
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182 e = -e;
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183 /*endif*/
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184 linear = s->last + e;
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185
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186 /* Saturate the values to +/- 2^11 (supposed to be 12 bits) */
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187 if (linear > 2047)
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188 linear = 2047;
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189 else if (linear < -2048)
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190 linear = -2048;
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191 /*endif*/
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192
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193 s->last = linear;
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194 s->step_index += step_adjustment[adpcm & 0x07];
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195 if (s->step_index < 0)
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196 s->step_index = 0;
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197 else if (s->step_index > 48)
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198 s->step_index = 48;
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199 /*endif*/
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200 /* Note: the result here is a 12 bit value */
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201 return linear;
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202 }
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203 /*- End of function --------------------------------------------------------*/
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204
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205 static uint8_t encode(oki_adpcm_state_t *s, int16_t linear)
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206 {
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207 int16_t e;
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208 int16_t ss;
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209 uint8_t adpcm;
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210
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211 ss = step_size[s->step_index];
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212 e = (linear >> 4) - s->last;
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213 adpcm = (uint8_t) 0x00;
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214 if (e < 0)
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215 {
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216 adpcm = (uint8_t) 0x08;
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217 e = -e;
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218 }
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219 /*endif*/
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220 if (e >= ss)
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221 {
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222 adpcm |= (uint8_t) 0x04;
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223 e -= ss;
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224 }
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225 /*endif*/
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226 if (e >= (ss >> 1))
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227 {
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228 adpcm |= (uint8_t) 0x02;
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229 e -= ss;
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230 }
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231 /*endif*/
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232 if (e >= (ss >> 2))
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233 adpcm |= (uint8_t) 0x01;
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234 /*endif*/
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235
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236 /* Use the decoder to set the estimate of the last sample. */
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237 /* It also will adjust the step_index for us. */
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238 s->last = decode(s, adpcm);
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239 return adpcm;
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240 }
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241 /*- End of function --------------------------------------------------------*/
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242
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243 oki_adpcm_state_t *oki_adpcm_init(oki_adpcm_state_t *s, int bit_rate)
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244 {
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245 if (bit_rate != 32000 && bit_rate != 24000)
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246 return NULL;
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247 if (s == NULL)
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248 {
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249 if ((s = (oki_adpcm_state_t *) malloc(sizeof(*s))) == NULL)
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250 return NULL;
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251 }
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252 memset(s, 0, sizeof(*s));
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253 s->bit_rate = bit_rate;
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254
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255 return s;
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256 }
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257 /*- End of function --------------------------------------------------------*/
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258
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259 int oki_adpcm_release(oki_adpcm_state_t *s)
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260 {
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261 free(s);
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262 return 0;
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263 }
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264 /*- End of function --------------------------------------------------------*/
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265
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266 int oki_adpcm_decode(oki_adpcm_state_t *s,
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267 int16_t amp[],
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268 const uint8_t oki_data[],
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269 int oki_bytes)
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270 {
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271 int i;
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272 int x;
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273 int l;
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274 int n;
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275 int samples;
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276 float z;
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277
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278 samples = 0;
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279 if (s->bit_rate == 32000)
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280 {
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281 for (i = 0; i < oki_bytes; i++)
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282 {
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283 amp[samples++] = decode(s, (oki_data[i] >> 4) & 0xF) << 4;
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284 amp[samples++] = decode(s, oki_data[i] & 0xF) << 4;
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285 }
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286 /*endwhile*/
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287 }
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288 else
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289 {
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290 n = 0;
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291 for (i = 0; i < oki_bytes; )
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292 {
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293 /* 6k to 8k sample/second conversion */
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294 if (s->phase)
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295 {
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296 s->history[s->ptr++] =
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297 decode(s, (n++ & 1) ? (oki_data[i++] & 0xF) : ((oki_data[i] >> 4) & 0xF)) << 4;
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298 s->ptr &= (32 - 1);
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299 }
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300 /*endif*/
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301 z = 0.0f;
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302 for (l = 80 - 3 + s->phase, x = s->ptr - 1; l >= 0; l -= 4, x--)
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303 z += cutoff_coeffs[l]*s->history[x & (32 - 1)];
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304 amp[samples++] = (int16_t) (z*4.0f);
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305 if (++s->phase > 3)
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306 s->phase = 0;
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307 /*endif*/
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308 }
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309 /*endfor*/
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310 }
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311 /*endif*/
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312 return samples;
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313 }
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314 /*- End of function --------------------------------------------------------*/
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315
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316 int oki_adpcm_encode(oki_adpcm_state_t *s,
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317 uint8_t oki_data[],
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318 const int16_t amp[],
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319 int len)
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320 {
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321 int x;
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322 int l;
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323 int n;
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324 int bytes;
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325 float z;
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326
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327 bytes = 0;
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328 if (s->bit_rate == 32000)
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329 {
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330 for (n = 0; n < len; n++)
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331 {
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332 s->oki_byte = (s->oki_byte << 4) | encode(s, amp[n]);
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333 if ((s->mark++ & 1))
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334 oki_data[bytes++] = s->oki_byte;
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335 /*endif*/
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336 }
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337 /*endfor*/
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338 }
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339 else
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340 {
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341 n = 0;
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342 for (;;)
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343 {
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344 /* 8k to 6k sample/second conversion */
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345 if (s->phase > 2)
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346 {
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347 s->history[s->ptr++] = amp[n];
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348 s->ptr &= (32 - 1);
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349 s->phase = 0;
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350 if (++n >= len)
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351 break;
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352 /*endif*/
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353 }
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354 /*endif*/
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355 s->history[s->ptr++] = amp[n];
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356 s->ptr &= (32 - 1);
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357 z = 0.0f;
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358 for (l = 80 - s->phase, x = s->ptr - 1; l >= 0; l -= 3, x--)
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359 z += cutoff_coeffs[l]*s->history[x & (32 - 1)];
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360 /*endfor*/
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361 s->oki_byte = (s->oki_byte << 4) | encode(s, (int16_t) (z*3.0f));
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362 if ((s->mark++ & 1))
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363 oki_data[bytes++] = s->oki_byte;
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364 /*endif*/
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365 s->phase++;
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366 if (++n >= len)
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367 break;
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368 /*endif*/
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369 }
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370 /*endfor*/
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371 }
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372 /*endif*/
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373 return bytes;
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374 }
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375 /*- End of function --------------------------------------------------------*/
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376 /*- End of file ------------------------------------------------------------*/
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