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1 <?php
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2 // +----------------------------------------------------------------------+
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3 // | PHP version 5 |
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4 // +----------------------------------------------------------------------+
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5 // | Copyright (c) 2002-2006 James Heinrich, Allan Hansen |
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6 // +----------------------------------------------------------------------+
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7 // | This source file is subject to version 2 of the GPL license, |
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8 // | that is bundled with this package in the file license.txt and is |
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9 // | available through the world-wide-web at the following url: |
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10 // | http://www.gnu.org/copyleft/gpl.html |
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11 // +----------------------------------------------------------------------+
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12 // | getID3() - http://getid3.sourceforge.net or http://www.getid3.org |
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13 // +----------------------------------------------------------------------+
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14 // | Authors: James Heinrich <infoŘgetid3*org> |
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15 // | Allan Hansen <ahŘartemis*dk> |
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16 // +----------------------------------------------------------------------+
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17 // | module.audio.ac3.php |
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18 // | Module for analyzing AC-3 (aka Dolby Digital) audio files |
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19 // | dependencies: NONE |
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20 // +----------------------------------------------------------------------+
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21 //
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22 // $Id: module.audio.ac3.php,v 1.3 2006/11/02 10:48:01 ah Exp $
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23
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24
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25
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26 class getid3_ac3 extends getid3_handler
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27 {
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28
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29 public function Analyze() {
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30
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31 $getid3 = $this->getid3;
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32
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33 // http://www.atsc.org/standards/a_52a.pdf
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34
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35 $getid3->info['fileformat'] = 'ac3';
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36 $getid3->info['audio']['dataformat'] = 'ac3';
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37 $getid3->info['audio']['bitrate_mode'] = 'cbr';
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38 $getid3->info['audio']['lossless'] = false;
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39
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40 $getid3->info['ac3']['raw']['bsi'] = array ();
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41 $info_ac3 = &$getid3->info['ac3'];
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42 $info_ac3_raw = &$info_ac3['raw'];
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43 $info_ac3_raw_bsi = &$info_ac3_raw['bsi'];
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44
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45
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46 // An AC-3 serial coded audio bit stream is made up of a sequence of synchronization frames
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47 // Each synchronization frame contains 6 coded audio blocks (AB), each of which represent 256
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48 // new audio samples per channel. A synchronization information (SI) header at the beginning
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49 // of each frame contains information needed to acquire and maintain synchronization. A
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50 // bit stream information (BSI) header follows SI, and contains parameters describing the coded
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51 // audio service. The coded audio blocks may be followed by an auxiliary data (Aux) field. At the
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52 // end of each frame is an error check field that includes a CRC word for error detection. An
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53 // additional CRC word is located in the SI header, the use of which, by a decoder, is optional.
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54 //
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55 // syncinfo() | bsi() | AB0 | AB1 | AB2 | AB3 | AB4 | AB5 | Aux | CRC
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56
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57 $this->fseek($getid3->info['avdataoffset'], SEEK_SET);
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58 $ac3_header['syncinfo'] = $this->fread(5);
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59 $info_ac3_raw['synchinfo']['synchword'] = substr($ac3_header['syncinfo'], 0, 2);
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60
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61 if ($info_ac3_raw['synchinfo']['synchword'] != "\x0B\x77") {
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62 throw new getid3_exception('Expecting "\x0B\x77" at offset '.$getid3->info['avdataoffset'].', found \x'.strtoupper(dechex($ac3_header['syncinfo']{0})).'\x'.strtoupper(dechex($ac3_header['syncinfo']{1})).' instead');
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63 }
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64
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65
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66 // syncinfo() {
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67 // syncword 16
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68 // crc1 16
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69 // fscod 2
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70 // frmsizecod 6
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71 // } /* end of syncinfo */
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72
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73 $info_ac3_raw['synchinfo']['crc1'] = getid3_lib::LittleEndian2Int(substr($ac3_header['syncinfo'], 2, 2));
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74 $ac3_synchinfo_fscod_frmsizecod = getid3_lib::LittleEndian2Int(substr($ac3_header['syncinfo'], 4, 1));
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75 $info_ac3_raw['synchinfo']['fscod'] = ($ac3_synchinfo_fscod_frmsizecod & 0xC0) >> 6;
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76 $info_ac3_raw['synchinfo']['frmsizecod'] = ($ac3_synchinfo_fscod_frmsizecod & 0x3F);
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77
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78 $info_ac3['sample_rate'] = getid3_ac3::AC3sampleRateCodeLookup($info_ac3_raw['synchinfo']['fscod']);
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79 if ($info_ac3_raw['synchinfo']['fscod'] <= 3) {
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80 $getid3->info['audio']['sample_rate'] = $info_ac3['sample_rate'];
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81 }
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82
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83 $info_ac3['frame_length'] = getid3_ac3::AC3frameSizeLookup($info_ac3_raw['synchinfo']['frmsizecod'], $info_ac3_raw['synchinfo']['fscod']);
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84 $info_ac3['bitrate'] = getid3_ac3::AC3bitrateLookup($info_ac3_raw['synchinfo']['frmsizecod']);
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85 $getid3->info['audio']['bitrate'] = $info_ac3['bitrate'];
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86
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87 $ac3_header['bsi'] = getid3_lib::BigEndian2Bin($this->fread(15));
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88
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89 $info_ac3_raw_bsi['bsid'] = bindec(substr($ac3_header['bsi'], 0, 5));
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90 if ($info_ac3_raw_bsi['bsid'] > 8) {
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91 // Decoders which can decode version 8 will thus be able to decode version numbers less than 8.
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92 // If this standard is extended by the addition of additional elements or features, a value of bsid greater than 8 will be used.
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93 // Decoders built to this version of the standard will not be able to decode versions with bsid greater than 8.
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94 throw new getid3_exception('Bit stream identification is version '.$info_ac3_raw_bsi['bsid'].', but getID3() only understands up to version 8');
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95 }
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96
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97 $info_ac3_raw_bsi['bsmod'] = bindec(substr($ac3_header['bsi'], 5, 3));
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98 $info_ac3_raw_bsi['acmod'] = bindec(substr($ac3_header['bsi'], 8, 3));
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99
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100 $info_ac3['service_type'] = getid3_ac3::AC3serviceTypeLookup($info_ac3_raw_bsi['bsmod'], $info_ac3_raw_bsi['acmod']);
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101 $ac3_coding_mode = getid3_ac3::AC3audioCodingModeLookup($info_ac3_raw_bsi['acmod']);
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102 foreach($ac3_coding_mode as $key => $value) {
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103 $info_ac3[$key] = $value;
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104 }
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105 switch ($info_ac3_raw_bsi['acmod']) {
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106 case 0:
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107 case 1:
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108 $getid3->info['audio']['channelmode'] = 'mono';
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109 break;
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110 case 3:
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111 case 4:
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112 $getid3->info['audio']['channelmode'] = 'stereo';
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113 break;
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114 default:
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115 $getid3->info['audio']['channelmode'] = 'surround';
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116 break;
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117 }
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118 $getid3->info['audio']['channels'] = $info_ac3['num_channels'];
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119
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120 $offset = 11;
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121
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122 if ($info_ac3_raw_bsi['acmod'] & 0x01) {
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123 // If the lsb of acmod is a 1, center channel is in use and cmixlev follows in the bit stream.
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124 $info_ac3_raw_bsi['cmixlev'] = bindec(substr($ac3_header['bsi'], $offset, 2));
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125 $info_ac3['center_mix_level'] = getid3_ac3::AC3centerMixLevelLookup($info_ac3_raw_bsi['cmixlev']);
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126 $offset += 2;
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127 }
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128
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129 if ($info_ac3_raw_bsi['acmod'] & 0x04) {
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130 // If the msb of acmod is a 1, surround channels are in use and surmixlev follows in the bit stream.
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131 $info_ac3_raw_bsi['surmixlev'] = bindec(substr($ac3_header['bsi'], $offset, 2));
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132 $info_ac3['surround_mix_level'] = getid3_ac3::AC3surroundMixLevelLookup($info_ac3_raw_bsi['surmixlev']);
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133 $offset += 2;
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134 }
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135
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136 if ($info_ac3_raw_bsi['acmod'] == 0x02) {
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137 // When operating in the two channel mode, this 2-bit code indicates whether or not the program has been encoded in Dolby Surround.
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138 $info_ac3_raw_bsi['dsurmod'] = bindec(substr($ac3_header['bsi'], $offset, 2));
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139 $info_ac3['dolby_surround_mode'] = getid3_ac3::AC3dolbySurroundModeLookup($info_ac3_raw_bsi['dsurmod']);
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140 $offset += 2;
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141 }
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142
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143 $info_ac3_raw_bsi['lfeon'] = $ac3_header['bsi']{$offset++} == '1';
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144 $info_ac3['lfe_enabled'] = $info_ac3_raw_bsi['lfeon'];
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145 if ($info_ac3_raw_bsi['lfeon']) {
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146 $getid3->info['audio']['channels'] .= '.1';
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147 }
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148
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149 $info_ac3['channels_enabled'] = getid3_ac3::AC3channelsEnabledLookup($info_ac3_raw_bsi['acmod'], $info_ac3_raw_bsi['lfeon']);
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150
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151 // This indicates how far the average dialogue level is below digital 100 percent. Valid values are 1–31.
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152 // The value of 0 is reserved. The values of 1 to 31 are interpreted as -1 dB to -31 dB with respect to digital 100 percent.
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153 $info_ac3_raw_bsi['dialnorm'] = bindec(substr($ac3_header['bsi'], $offset, 5));
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154 $offset += 5;
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155 $info_ac3['dialogue_normalization'] = '-'.$info_ac3_raw_bsi['dialnorm'].'dB';
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156
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157 $info_ac3_raw_bsi['compre_flag'] = $ac3_header['bsi']{$offset++} == '1';
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158 if ($info_ac3_raw_bsi['compre_flag']) {
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159 $info_ac3_raw_bsi['compr'] = bindec(substr($ac3_header['bsi'], $offset, 8));
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160 $offset += 8;
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161
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162 $info_ac3['heavy_compression'] = getid3_ac3::AC3heavyCompression($info_ac3_raw_bsi['compr']);
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163 }
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164
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165 $info_ac3_raw_bsi['langcode_flag'] = $ac3_header['bsi']{$offset++} == '1';
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166 if ($info_ac3_raw_bsi['langcode_flag']) {
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167 $info_ac3_raw_bsi['langcod'] = bindec(substr($ac3_header['bsi'], $offset, 8));
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168 $offset += 8;
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169 }
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170
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171 $info_ac3_raw_bsi['audprodie'] = $ac3_header['bsi']{$offset++} == '1';
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172 if ($info_ac3_raw_bsi['audprodie']) {
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173 $info_ac3_raw_bsi['mixlevel'] = bindec(substr($ac3_header['bsi'], $offset, 5));
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174 $offset += 5;
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175
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176 $info_ac3_raw_bsi['roomtyp'] = bindec(substr($ac3_header['bsi'], $offset, 2));
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177 $offset += 2;
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178
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179 $info_ac3['mixing_level'] = (80 + $info_ac3_raw_bsi['mixlevel']).'dB';
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180 $info_ac3['room_type'] = getid3_ac3::AC3roomTypeLookup($info_ac3_raw_bsi['roomtyp']);
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181 }
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182
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183 if ($info_ac3_raw_bsi['acmod'] == 0x00) {
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184 // If acmod is 0, then two completely independent program channels (dual mono)
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185 // are encoded into the bit stream, and are referenced as Ch1, Ch2. In this case,
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186 // a number of additional items are present in BSI or audblk to fully describe Ch2.
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187
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188
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189 // This indicates how far the average dialogue level is below digital 100 percent. Valid values are 1–31.
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190 // The value of 0 is reserved. The values of 1 to 31 are interpreted as -1 dB to -31 dB with respect to digital 100 percent.
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191 $info_ac3_raw_bsi['dialnorm2'] = bindec(substr($ac3_header['bsi'], $offset, 5));
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192 $offset += 5;
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193
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194 $info_ac3['dialogue_normalization2'] = '-'.$info_ac3_raw_bsi['dialnorm2'].'dB';
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195
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196 $info_ac3_raw_bsi['compre_flag2'] = $ac3_header['bsi']{$offset++} == '1';
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197 if ($info_ac3_raw_bsi['compre_flag2']) {
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198 $info_ac3_raw_bsi['compr2'] = bindec(substr($ac3_header['bsi'], $offset, 8));
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199 $offset += 8;
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200
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201 $info_ac3['heavy_compression2'] = getid3_ac3::AC3heavyCompression($info_ac3_raw_bsi['compr2']);
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202 }
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203
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204 $info_ac3_raw_bsi['langcode_flag2'] = $ac3_header['bsi']{$offset++} == '1';
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205 if ($info_ac3_raw_bsi['langcode_flag2']) {
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206 $info_ac3_raw_bsi['langcod2'] = bindec(substr($ac3_header['bsi'], $offset, 8));
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207 $offset += 8;
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208 }
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209
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210 $info_ac3_raw_bsi['audprodie2'] = $ac3_header['bsi']{$offset++} == '1';
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211 if ($info_ac3_raw_bsi['audprodie2']) {
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212 $info_ac3_raw_bsi['mixlevel2'] = bindec(substr($ac3_header['bsi'], $offset, 5));
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213 $offset += 5;
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214
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215 $info_ac3_raw_bsi['roomtyp2'] = bindec(substr($ac3_header['bsi'], $offset, 2));
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216 $offset += 2;
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217
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218 $info_ac3['mixing_level2'] = (80 + $info_ac3_raw_bsi['mixlevel2']).'dB';
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219 $info_ac3['room_type2'] = getid3_ac3::AC3roomTypeLookup($info_ac3_raw_bsi['roomtyp2']);
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220 }
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221
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222 }
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223
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224 $info_ac3_raw_bsi['copyright'] = $ac3_header['bsi']{$offset++} == '1';
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225
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226 $info_ac3_raw_bsi['original'] = $ac3_header['bsi']{$offset++} == '1';
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227
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228 $info_ac3_raw_bsi['timecode1_flag'] = $ac3_header['bsi']{$offset++} == '1';
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229 if ($info_ac3_raw_bsi['timecode1_flag']) {
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230 $info_ac3_raw_bsi['timecode1'] = bindec(substr($ac3_header['bsi'], $offset, 14));
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231 $offset += 14;
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232 }
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233
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234 $info_ac3_raw_bsi['timecode2_flag'] = $ac3_header['bsi']{$offset++} == '1';
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235 if ($info_ac3_raw_bsi['timecode2_flag']) {
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236 $info_ac3_raw_bsi['timecode2'] = bindec(substr($ac3_header['bsi'], $offset, 14));
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237 $offset += 14;
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238 }
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239
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240 $info_ac3_raw_bsi['addbsi_flag'] = $ac3_header['bsi']{$offset++} == '1';
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241 if ($info_ac3_raw_bsi['addbsi_flag']) {
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242 $info_ac3_raw_bsi['addbsi_length'] = bindec(substr($ac3_header['bsi'], $offset, 6));
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243 $offset += 6;
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244
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245 $ac3_header['bsi'] .= getid3_lib::BigEndian2Bin($this->fread($info_ac3_raw_bsi['addbsi_length']));
|
|
rlm@3
|
246
|
|
rlm@3
|
247 $info_ac3_raw_bsi['addbsi_data'] = substr($ac3_header['bsi'], 119, $info_ac3_raw_bsi['addbsi_length'] * 8);
|
|
rlm@3
|
248 }
|
|
rlm@3
|
249
|
|
rlm@3
|
250 return true;
|
|
rlm@3
|
251 }
|
|
rlm@3
|
252
|
|
rlm@3
|
253
|
|
rlm@3
|
254
|
|
rlm@3
|
255 public static function AC3sampleRateCodeLookup($fscod) {
|
|
rlm@3
|
256
|
|
rlm@3
|
257 static $lookup = array (
|
|
rlm@3
|
258 0 => 48000,
|
|
rlm@3
|
259 1 => 44100,
|
|
rlm@3
|
260 2 => 32000,
|
|
rlm@3
|
261 3 => 'reserved' // If the reserved code is indicated, the decoder should not attempt to decode audio and should mute.
|
|
rlm@3
|
262 );
|
|
rlm@3
|
263 return (isset($lookup[$fscod]) ? $lookup[$fscod] : false);
|
|
rlm@3
|
264 }
|
|
rlm@3
|
265
|
|
rlm@3
|
266
|
|
rlm@3
|
267
|
|
rlm@3
|
268 public static function AC3serviceTypeLookup($bsmod, $acmod) {
|
|
rlm@3
|
269
|
|
rlm@3
|
270 static $lookup = array (
|
|
rlm@3
|
271 0 => 'main audio service: complete main (CM)',
|
|
rlm@3
|
272 1 => 'main audio service: music and effects (ME)',
|
|
rlm@3
|
273 2 => 'associated service: visually impaired (VI)',
|
|
rlm@3
|
274 3 => 'associated service: hearing impaired (HI)',
|
|
rlm@3
|
275 4 => 'associated service: dialogue (D)',
|
|
rlm@3
|
276 5 => 'associated service: commentary (C)',
|
|
rlm@3
|
277 6 => 'associated service: emergency (E)',
|
|
rlm@3
|
278 7 => 'main audio service: karaoke'
|
|
rlm@3
|
279 );
|
|
rlm@3
|
280
|
|
rlm@3
|
281 if ($bsmod == 7 && $acmod == 1) {
|
|
rlm@3
|
282 return 'associated service: voice over (VO)';
|
|
rlm@3
|
283 }
|
|
rlm@3
|
284
|
|
rlm@3
|
285 return (isset($lookup[$bsmod]) ? $lookup[$bsmod] : false);
|
|
rlm@3
|
286 }
|
|
rlm@3
|
287
|
|
rlm@3
|
288
|
|
rlm@3
|
289
|
|
rlm@3
|
290 public static function AC3audioCodingModeLookup($acmod) {
|
|
rlm@3
|
291
|
|
rlm@3
|
292 // array (channel configuration, # channels (not incl LFE), channel order)
|
|
rlm@3
|
293 static $lookup = array (
|
|
rlm@3
|
294 0 => array ('channel_config'=>'1+1', 'num_channels'=>2, 'channel_order'=>'Ch1,Ch2'),
|
|
rlm@3
|
295 1 => array ('channel_config'=>'1/0', 'num_channels'=>1, 'channel_order'=>'C'),
|
|
rlm@3
|
296 2 => array ('channel_config'=>'2/0', 'num_channels'=>2, 'channel_order'=>'L,R'),
|
|
rlm@3
|
297 3 => array ('channel_config'=>'3/0', 'num_channels'=>3, 'channel_order'=>'L,C,R'),
|
|
rlm@3
|
298 4 => array ('channel_config'=>'2/1', 'num_channels'=>3, 'channel_order'=>'L,R,S'),
|
|
rlm@3
|
299 5 => array ('channel_config'=>'3/1', 'num_channels'=>4, 'channel_order'=>'L,C,R,S'),
|
|
rlm@3
|
300 6 => array ('channel_config'=>'2/2', 'num_channels'=>4, 'channel_order'=>'L,R,SL,SR'),
|
|
rlm@3
|
301 7 => array ('channel_config'=>'3/2', 'num_channels'=>5, 'channel_order'=>'L,C,R,SL,SR')
|
|
rlm@3
|
302 );
|
|
rlm@3
|
303 return (isset($lookup[$acmod]) ? $lookup[$acmod] : false);
|
|
rlm@3
|
304 }
|
|
rlm@3
|
305
|
|
rlm@3
|
306
|
|
rlm@3
|
307
|
|
rlm@3
|
308 public static function AC3centerMixLevelLookup($cmixlev) {
|
|
rlm@3
|
309
|
|
rlm@3
|
310 static $lookup;
|
|
rlm@3
|
311 if (!@$lookup) {
|
|
rlm@3
|
312 $lookup = array (
|
|
rlm@3
|
313 0 => pow(2, -3.0 / 6), // 0.707 (–3.0 dB)
|
|
rlm@3
|
314 1 => pow(2, -4.5 / 6), // 0.595 (–4.5 dB)
|
|
rlm@3
|
315 2 => pow(2, -6.0 / 6), // 0.500 (–6.0 dB)
|
|
rlm@3
|
316 3 => 'reserved'
|
|
rlm@3
|
317 );
|
|
rlm@3
|
318 }
|
|
rlm@3
|
319 return (isset($lookup[$cmixlev]) ? $lookup[$cmixlev] : false);
|
|
rlm@3
|
320 }
|
|
rlm@3
|
321
|
|
rlm@3
|
322
|
|
rlm@3
|
323
|
|
rlm@3
|
324 public static function AC3surroundMixLevelLookup($surmixlev) {
|
|
rlm@3
|
325
|
|
rlm@3
|
326 static $lookup;
|
|
rlm@3
|
327 if (!@$lookup) {
|
|
rlm@3
|
328 $lookup = array (
|
|
rlm@3
|
329 0 => pow(2, -3.0 / 6),
|
|
rlm@3
|
330 1 => pow(2, -6.0 / 6),
|
|
rlm@3
|
331 2 => 0,
|
|
rlm@3
|
332 3 => 'reserved'
|
|
rlm@3
|
333 );
|
|
rlm@3
|
334 }
|
|
rlm@3
|
335 return (isset($lookup[$surmixlev]) ? $lookup[$surmixlev] : false);
|
|
rlm@3
|
336 }
|
|
rlm@3
|
337
|
|
rlm@3
|
338
|
|
rlm@3
|
339
|
|
rlm@3
|
340 public static function AC3dolbySurroundModeLookup($dsurmod) {
|
|
rlm@3
|
341
|
|
rlm@3
|
342 static $lookup = array (
|
|
rlm@3
|
343 0 => 'not indicated',
|
|
rlm@3
|
344 1 => 'Not Dolby Surround encoded',
|
|
rlm@3
|
345 2 => 'Dolby Surround encoded',
|
|
rlm@3
|
346 3 => 'reserved'
|
|
rlm@3
|
347 );
|
|
rlm@3
|
348 return (isset($lookup[$dsurmod]) ? $lookup[$dsurmod] : false);
|
|
rlm@3
|
349 }
|
|
rlm@3
|
350
|
|
rlm@3
|
351
|
|
rlm@3
|
352
|
|
rlm@3
|
353 public static function AC3channelsEnabledLookup($acmod, $lfeon) {
|
|
rlm@3
|
354
|
|
rlm@3
|
355 return array (
|
|
rlm@3
|
356 'ch1' => $acmod == 0,
|
|
rlm@3
|
357 'ch2' => $acmod == 0,
|
|
rlm@3
|
358 'left' => $acmod > 1,
|
|
rlm@3
|
359 'right' => $acmod > 1,
|
|
rlm@3
|
360 'center' => (bool)($acmod & 0x01),
|
|
rlm@3
|
361 'surround_mono' => $acmod == 4 || $acmod == 5,
|
|
rlm@3
|
362 'surround_left' => $acmod == 6 || $acmod == 7,
|
|
rlm@3
|
363 'surround_right' => $acmod == 6 || $acmod == 7,
|
|
rlm@3
|
364 'lfe' => $lfeon
|
|
rlm@3
|
365 );
|
|
rlm@3
|
366 }
|
|
rlm@3
|
367
|
|
rlm@3
|
368
|
|
rlm@3
|
369
|
|
rlm@3
|
370 public static function AC3heavyCompression($compre) {
|
|
rlm@3
|
371
|
|
rlm@3
|
372 // The first four bits indicate gain changes in 6.02dB increments which can be
|
|
rlm@3
|
373 // implemented with an arithmetic shift operation. The following four bits
|
|
rlm@3
|
374 // indicate linear gain changes, and require a 5-bit multiply.
|
|
rlm@3
|
375 // We will represent the two 4-bit fields of compr as follows:
|
|
rlm@3
|
376 // X0 X1 X2 X3 . Y4 Y5 Y6 Y7
|
|
rlm@3
|
377 // The meaning of the X values is most simply described by considering X to represent a 4-bit
|
|
rlm@3
|
378 // signed integer with values from –8 to +7. The gain indicated by X is then (X + 1) * 6.02 dB. The
|
|
rlm@3
|
379 // following table shows this in detail.
|
|
rlm@3
|
380
|
|
rlm@3
|
381 // Meaning of 4 msb of compr
|
|
rlm@3
|
382 // 7 +48.16 dB
|
|
rlm@3
|
383 // 6 +42.14 dB
|
|
rlm@3
|
384 // 5 +36.12 dB
|
|
rlm@3
|
385 // 4 +30.10 dB
|
|
rlm@3
|
386 // 3 +24.08 dB
|
|
rlm@3
|
387 // 2 +18.06 dB
|
|
rlm@3
|
388 // 1 +12.04 dB
|
|
rlm@3
|
389 // 0 +6.02 dB
|
|
rlm@3
|
390 // -1 0 dB
|
|
rlm@3
|
391 // -2 –6.02 dB
|
|
rlm@3
|
392 // -3 –12.04 dB
|
|
rlm@3
|
393 // -4 –18.06 dB
|
|
rlm@3
|
394 // -5 –24.08 dB
|
|
rlm@3
|
395 // -6 –30.10 dB
|
|
rlm@3
|
396 // -7 –36.12 dB
|
|
rlm@3
|
397 // -8 –42.14 dB
|
|
rlm@3
|
398
|
|
rlm@3
|
399 $fourbit = str_pad(decbin(($compre & 0xF0) >> 4), 4, '0', STR_PAD_LEFT);
|
|
rlm@3
|
400 if ($fourbit{0} == '1') {
|
|
rlm@3
|
401 $log_gain = -8 + bindec(substr($fourbit, 1));
|
|
rlm@3
|
402 } else {
|
|
rlm@3
|
403 $log_gain = bindec(substr($fourbit, 1));
|
|
rlm@3
|
404 }
|
|
rlm@3
|
405 $log_gain = ($log_gain + 1) * (20 * log10(2));
|
|
rlm@3
|
406
|
|
rlm@3
|
407 // The value of Y is a linear representation of a gain change of up to –6 dB. Y is considered to
|
|
rlm@3
|
408 // be an unsigned fractional integer, with a leading value of 1, or: 0.1 Y4 Y5 Y6 Y7 (base 2). Y can
|
|
rlm@3
|
409 // represent values between 0.111112 (or 31/32) and 0.100002 (or 1/2). Thus, Y can represent gain
|
|
rlm@3
|
410 // changes from –0.28 dB to –6.02 dB.
|
|
rlm@3
|
411
|
|
rlm@3
|
412 $lin_gain = (16 + ($compre & 0x0F)) / 32;
|
|
rlm@3
|
413
|
|
rlm@3
|
414 // The combination of X and Y values allows compr to indicate gain changes from
|
|
rlm@3
|
415 // 48.16 – 0.28 = +47.89 dB, to
|
|
rlm@3
|
416 // –42.14 – 6.02 = –48.16 dB.
|
|
rlm@3
|
417
|
|
rlm@3
|
418 return $log_gain - $lin_gain;
|
|
rlm@3
|
419 }
|
|
rlm@3
|
420
|
|
rlm@3
|
421
|
|
rlm@3
|
422
|
|
rlm@3
|
423 public static function AC3roomTypeLookup($roomtyp) {
|
|
rlm@3
|
424
|
|
rlm@3
|
425 static $lookup = array (
|
|
rlm@3
|
426 0 => 'not indicated',
|
|
rlm@3
|
427 1 => 'large room, X curve monitor',
|
|
rlm@3
|
428 2 => 'small room, flat monitor',
|
|
rlm@3
|
429 3 => 'reserved'
|
|
rlm@3
|
430 );
|
|
rlm@3
|
431 return (isset($lookup[$roomtyp]) ? $lookup[$roomtyp] : false);
|
|
rlm@3
|
432 }
|
|
rlm@3
|
433
|
|
rlm@3
|
434
|
|
rlm@3
|
435
|
|
rlm@3
|
436 public static function AC3frameSizeLookup($frmsizecod, $fscod) {
|
|
rlm@3
|
437
|
|
rlm@3
|
438 $padding = (bool)($frmsizecod % 2);
|
|
rlm@3
|
439 $frame_size_id = floor($frmsizecod / 2);
|
|
rlm@3
|
440
|
|
rlm@3
|
441 static $lookup = array (
|
|
rlm@3
|
442 0 => array (128, 138, 192),
|
|
rlm@3
|
443 1 => array (40, 160, 174, 240),
|
|
rlm@3
|
444 2 => array (48, 192, 208, 288),
|
|
rlm@3
|
445 3 => array (56, 224, 242, 336),
|
|
rlm@3
|
446 4 => array (64, 256, 278, 384),
|
|
rlm@3
|
447 5 => array (80, 320, 348, 480),
|
|
rlm@3
|
448 6 => array (96, 384, 416, 576),
|
|
rlm@3
|
449 7 => array (112, 448, 486, 672),
|
|
rlm@3
|
450 8 => array (128, 512, 556, 768),
|
|
rlm@3
|
451 9 => array (160, 640, 696, 960),
|
|
rlm@3
|
452 10 => array (192, 768, 834, 1152),
|
|
rlm@3
|
453 11 => array (224, 896, 974, 1344),
|
|
rlm@3
|
454 12 => array (256, 1024, 1114, 1536),
|
|
rlm@3
|
455 13 => array (320, 1280, 1392, 1920),
|
|
rlm@3
|
456 14 => array (384, 1536, 1670, 2304),
|
|
rlm@3
|
457 15 => array (448, 1792, 1950, 2688),
|
|
rlm@3
|
458 16 => array (512, 2048, 2228, 3072),
|
|
rlm@3
|
459 17 => array (576, 2304, 2506, 3456),
|
|
rlm@3
|
460 18 => array (640, 2560, 2786, 3840)
|
|
rlm@3
|
461 );
|
|
rlm@3
|
462 if (($fscod == 1) && $padding) {
|
|
rlm@3
|
463 // frame lengths are padded by 1 word (16 bits) at 44100
|
|
rlm@3
|
464 $lookup[$frmsizecod] += 2;
|
|
rlm@3
|
465 }
|
|
rlm@3
|
466 return (isset($lookup[$frame_size_id][$fscod]) ? $lookup[$frame_size_id][$fscod] : false);
|
|
rlm@3
|
467 }
|
|
rlm@3
|
468
|
|
rlm@3
|
469
|
|
rlm@3
|
470
|
|
rlm@3
|
471 public static function AC3bitrateLookup($frmsizecod) {
|
|
rlm@3
|
472
|
|
rlm@3
|
473 static $lookup = array (
|
|
rlm@3
|
474 0 => 32000,
|
|
rlm@3
|
475 1 => 40000,
|
|
rlm@3
|
476 2 => 48000,
|
|
rlm@3
|
477 3 => 56000,
|
|
rlm@3
|
478 4 => 64000,
|
|
rlm@3
|
479 5 => 80000,
|
|
rlm@3
|
480 6 => 96000,
|
|
rlm@3
|
481 7 => 112000,
|
|
rlm@3
|
482 8 => 128000,
|
|
rlm@3
|
483 9 => 160000,
|
|
rlm@3
|
484 10 => 192000,
|
|
rlm@3
|
485 11 => 224000,
|
|
rlm@3
|
486 12 => 256000,
|
|
rlm@3
|
487 13 => 320000,
|
|
rlm@3
|
488 14 => 384000,
|
|
rlm@3
|
489 15 => 448000,
|
|
rlm@3
|
490 16 => 512000,
|
|
rlm@3
|
491 17 => 576000,
|
|
rlm@3
|
492 18 => 640000
|
|
rlm@3
|
493 );
|
|
rlm@3
|
494 $frame_size_id = floor($frmsizecod / 2);
|
|
rlm@3
|
495 return (isset($lookup[$frame_size_id]) ? $lookup[$frame_size_id] : false);
|
|
rlm@3
|
496 }
|
|
rlm@3
|
497
|
|
rlm@3
|
498 }
|
|
rlm@3
|
499
|
|
rlm@3
|
500 ?> |
