wp-includes/ID3/module.audio.ac3.php

   1 <?php
   2 /////////////////////////////////////////////////////////////////
   3 /// getID3() by James Heinrich <info@getid3.org>               //
   4 //  available at http://getid3.sourceforge.net                 //
   5 //            or http://www.getid3.org                         //
   6 //          also https://github.com/JamesHeinrich/getID3       //
   7 /////////////////////////////////////////////////////////////////
   8 // See readme.txt for more details                             //
   9 /////////////////////////////////////////////////////////////////
  10 //                                                             //
  11 // module.audio.ac3.php                                        //
  12 // module for analyzing AC-3 (aka Dolby Digital) audio files   //
  13 // dependencies: NONE                                          //
  14 //                                                            ///
  15 /////////////////////////////////////////////////////////////////
  16
  17
  18 class getid3_ac3 extends getid3_handler
  19 {
  20     private $AC3header = array();
  21     private $BSIoffset = 0;
  22
  23     const syncword = "\x0B\x77";
  24
  25         public function Analyze() {
  26                 $info = &$this->getid3->info;
  27
  28                 ///AH
  29                 $info['ac3']['raw']['bsi'] = array();
  30                 $thisfile_ac3              = &$info['ac3'];
  31                 $thisfile_ac3_raw          = &$thisfile_ac3['raw'];
  32                 $thisfile_ac3_raw_bsi      = &$thisfile_ac3_raw['bsi'];
  33
  34
  35                 // http://www.atsc.org/standards/a_52a.pdf
  36
  37                 $info['fileformat'] = 'ac3';
  38
  39                 // An AC-3 serial coded audio bit stream is made up of a sequence of synchronization frames
  40                 // Each synchronization frame contains 6 coded audio blocks (AB), each of which represent 256
  41                 // new audio samples per channel. A synchronization information (SI) header at the beginning
  42                 // of each frame contains information needed to acquire and maintain synchronization. A
  43                 // bit stream information (BSI) header follows SI, and contains parameters describing the coded
  44                 // audio service. The coded audio blocks may be followed by an auxiliary data (Aux) field. At the
  45                 // end of each frame is an error check field that includes a CRC word for error detection. An
  46                 // additional CRC word is located in the SI header, the use of which, by a decoder, is optional.
  47                 //
  48                 // syncinfo() | bsi() | AB0 | AB1 | AB2 | AB3 | AB4 | AB5 | Aux | CRC
  49
  50                 // syncinfo() {
  51                 //       syncword    16
  52                 //       crc1        16
  53                 //       fscod        2
  54                 //       frmsizecod   6
  55                 // } /* end of syncinfo */
  56
  57                 $this->fseek($info['avdataoffset']);
  58                 $this->AC3header['syncinfo'] = $this->fread(5);
  59
  60                 if (strpos($this->AC3header['syncinfo'], self::syncword) === 0) {
  61                         $thisfile_ac3_raw['synchinfo']['synchword'] = self::syncword;
  62                         $offset = 2;
  63                 } else {
  64                         if (!$this->isDependencyFor('matroska')) {
  65                                 unset($info['fileformat'], $info['ac3']);
  66                                 return $this->error('Expecting "'.getid3_lib::PrintHexBytes(self::syncword).'" at offset '.$info['avdataoffset'].', found "'.getid3_lib::PrintHexBytes(substr($this->AC3header['syncinfo'], 0, 2)).'"');
  67                         }
  68                         $offset = 0;
  69                         $this->fseek(-2, SEEK_CUR);
  70                 }
  71
  72                 $info['audio']['dataformat']   = 'ac3';
  73                 $info['audio']['bitrate_mode'] = 'cbr';
  74                 $info['audio']['lossless']     = false;
  75
  76                 $thisfile_ac3_raw['synchinfo']['crc1']       = getid3_lib::LittleEndian2Int(substr($this->AC3header['syncinfo'], $offset, 2));
  77                 $ac3_synchinfo_fscod_frmsizecod              = getid3_lib::LittleEndian2Int(substr($this->AC3header['syncinfo'], ($offset + 2), 1));
  78                 $thisfile_ac3_raw['synchinfo']['fscod']      = ($ac3_synchinfo_fscod_frmsizecod & 0xC0) >> 6;
  79                 $thisfile_ac3_raw['synchinfo']['frmsizecod'] = ($ac3_synchinfo_fscod_frmsizecod & 0x3F);
  80
  81                 $thisfile_ac3['sample_rate'] = self::sampleRateCodeLookup($thisfile_ac3_raw['synchinfo']['fscod']);
  82                 if ($thisfile_ac3_raw['synchinfo']['fscod'] <= 3) {
  83                         $info['audio']['sample_rate'] = $thisfile_ac3['sample_rate'];
  84                 }
  85
  86                 $thisfile_ac3['frame_length'] = self::frameSizeLookup($thisfile_ac3_raw['synchinfo']['frmsizecod'], $thisfile_ac3_raw['synchinfo']['fscod']);
  87                 $thisfile_ac3['bitrate']      = self::bitrateLookup($thisfile_ac3_raw['synchinfo']['frmsizecod']);
  88                 $info['audio']['bitrate'] = $thisfile_ac3['bitrate'];
  89
  90                 $this->AC3header['bsi'] = getid3_lib::BigEndian2Bin($this->fread(15));
  91                 $ac3_bsi_offset = 0;
  92
  93                 $thisfile_ac3_raw_bsi['bsid'] = $this->readHeaderBSI(5);
  94                 if ($thisfile_ac3_raw_bsi['bsid'] > 8) {
  95                         // Decoders which can decode version 8 will thus be able to decode version numbers less than 8.
  96                         // If this standard is extended by the addition of additional elements or features, a value of bsid greater than 8 will be used.
  97                         // Decoders built to this version of the standard will not be able to decode versions with bsid greater than 8.
  98                         $this->error('Bit stream identification is version '.$thisfile_ac3_raw_bsi['bsid'].', but getID3() only understands up to version 8');
  99                     unset($info['ac3']);
 100                         return false;
 101                 }
 102
 103                 $thisfile_ac3_raw_bsi['bsmod'] = $this->readHeaderBSI(3);
 104                 $thisfile_ac3_raw_bsi['acmod'] = $this->readHeaderBSI(3);
 105
 106                 $thisfile_ac3['service_type'] = self::serviceTypeLookup($thisfile_ac3_raw_bsi['bsmod'], $thisfile_ac3_raw_bsi['acmod']);
 107                 $ac3_coding_mode = self::audioCodingModeLookup($thisfile_ac3_raw_bsi['acmod']);
 108                 foreach($ac3_coding_mode as $key => $value) {
 109                         $thisfile_ac3[$key] = $value;
 110                 }
 111                 switch ($thisfile_ac3_raw_bsi['acmod']) {
 112                         case 0:
 113                         case 1:
 114                                 $info['audio']['channelmode'] = 'mono';
 115                                 break;
 116                         case 3:
 117                         case 4:
 118                                 $info['audio']['channelmode'] = 'stereo';
 119                                 break;
 120                         default:
 121                                 $info['audio']['channelmode'] = 'surround';
 122                                 break;
 123                 }
 124                 $info['audio']['channels'] = $thisfile_ac3['num_channels'];
 125
 126                 if ($thisfile_ac3_raw_bsi['acmod'] & 0x01) {
 127                         // If the lsb of acmod is a 1, center channel is in use and cmixlev follows in the bit stream.
 128                         $thisfile_ac3_raw_bsi['cmixlev'] = $this->readHeaderBSI(2);
 129                         $thisfile_ac3['center_mix_level'] = self::centerMixLevelLookup($thisfile_ac3_raw_bsi['cmixlev']);
 130                 }
 131
 132                 if ($thisfile_ac3_raw_bsi['acmod'] & 0x04) {
 133                         // If the msb of acmod is a 1, surround channels are in use and surmixlev follows in the bit stream.
 134                         $thisfile_ac3_raw_bsi['surmixlev'] = $this->readHeaderBSI(2);
 135                         $thisfile_ac3['surround_mix_level'] = self::surroundMixLevelLookup($thisfile_ac3_raw_bsi['surmixlev']);
 136                 }
 137
 138                 if ($thisfile_ac3_raw_bsi['acmod'] == 0x02) {
 139                         // When operating in the two channel mode, this 2-bit code indicates whether or not the program has been encoded in Dolby Surround.
 140                         $thisfile_ac3_raw_bsi['dsurmod'] = $this->readHeaderBSI(2);
 141                         $thisfile_ac3['dolby_surround_mode'] = self::dolbySurroundModeLookup($thisfile_ac3_raw_bsi['dsurmod']);
 142                 }
 143
 144                 $thisfile_ac3_raw_bsi['lfeon'] = (bool) $this->readHeaderBSI(1);
 145                 $thisfile_ac3['lfe_enabled'] = $thisfile_ac3_raw_bsi['lfeon'];
 146                 if ($thisfile_ac3_raw_bsi['lfeon']) {
 147                         //$info['audio']['channels']++;
 148                         $info['audio']['channels'] .= '.1';
 149                 }
 150
 151                 $thisfile_ac3['channels_enabled'] = self::channelsEnabledLookup($thisfile_ac3_raw_bsi['acmod'], $thisfile_ac3_raw_bsi['lfeon']);
 152
 153                 // This indicates how far the average dialogue level is below digital 100 percent. Valid values are 1-31.
 154                 // 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.
 155                 $thisfile_ac3_raw_bsi['dialnorm'] = $this->readHeaderBSI(5);
 156                 $thisfile_ac3['dialogue_normalization'] = '-'.$thisfile_ac3_raw_bsi['dialnorm'].'dB';
 157
 158                 $thisfile_ac3_raw_bsi['compre_flag'] = (bool) $this->readHeaderBSI(1);
 159                 if ($thisfile_ac3_raw_bsi['compre_flag']) {
 160                         $thisfile_ac3_raw_bsi['compr'] = $this->readHeaderBSI(8);
 161                         $thisfile_ac3['heavy_compression'] = self::heavyCompression($thisfile_ac3_raw_bsi['compr']);
 162                 }
 163
 164                 $thisfile_ac3_raw_bsi['langcode_flag'] = (bool) $this->readHeaderBSI(1);
 165                 if ($thisfile_ac3_raw_bsi['langcode_flag']) {
 166                         $thisfile_ac3_raw_bsi['langcod'] = $this->readHeaderBSI(8);
 167                 }
 168
 169                 $thisfile_ac3_raw_bsi['audprodie'] = (bool) $this->readHeaderBSI(1);
 170                 if ($thisfile_ac3_raw_bsi['audprodie']) {
 171                         $thisfile_ac3_raw_bsi['mixlevel'] = $this->readHeaderBSI(5);
 172                         $thisfile_ac3_raw_bsi['roomtyp']  = $this->readHeaderBSI(2);
 173
 174                         $thisfile_ac3['mixing_level'] = (80 + $thisfile_ac3_raw_bsi['mixlevel']).'dB';
 175                         $thisfile_ac3['room_type']    = self::roomTypeLookup($thisfile_ac3_raw_bsi['roomtyp']);
 176                 }
 177
 178                 if ($thisfile_ac3_raw_bsi['acmod'] == 0x00) {
 179                         // If acmod is 0, then two completely independent program channels (dual mono)
 180                         // are encoded into the bit stream, and are referenced as Ch1, Ch2. In this case,
 181                         // a number of additional items are present in BSI or audblk to fully describe Ch2.
 182
 183                         // This indicates how far the average dialogue level is below digital 100 percent. Valid values are 1-31.
 184                         // 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.
 185                         $thisfile_ac3_raw_bsi['dialnorm2'] = $this->readHeaderBSI(5);
 186                         $thisfile_ac3['dialogue_normalization2'] = '-'.$thisfile_ac3_raw_bsi['dialnorm2'].'dB';
 187
 188                         $thisfile_ac3_raw_bsi['compre_flag2'] = (bool) $this->readHeaderBSI(1);
 189                         if ($thisfile_ac3_raw_bsi['compre_flag2']) {
 190                                 $thisfile_ac3_raw_bsi['compr2'] = $this->readHeaderBSI(8);
 191                                 $thisfile_ac3['heavy_compression2'] = self::heavyCompression($thisfile_ac3_raw_bsi['compr2']);
 192                         }
 193
 194                         $thisfile_ac3_raw_bsi['langcode_flag2'] = (bool) $this->readHeaderBSI(1);
 195                         if ($thisfile_ac3_raw_bsi['langcode_flag2']) {
 196                                 $thisfile_ac3_raw_bsi['langcod2'] = $this->readHeaderBSI(8);
 197                         }
 198
 199                         $thisfile_ac3_raw_bsi['audprodie2'] = (bool) $this->readHeaderBSI(1);
 200                         if ($thisfile_ac3_raw_bsi['audprodie2']) {
 201                                 $thisfile_ac3_raw_bsi['mixlevel2'] = $this->readHeaderBSI(5);
 202                                 $thisfile_ac3_raw_bsi['roomtyp2']  = $this->readHeaderBSI(2);
 203
 204                                 $thisfile_ac3['mixing_level2'] = (80 + $thisfile_ac3_raw_bsi['mixlevel2']).'dB';
 205                                 $thisfile_ac3['room_type2']    = self::roomTypeLookup($thisfile_ac3_raw_bsi['roomtyp2']);
 206                         }
 207
 208                 }
 209
 210                 $thisfile_ac3_raw_bsi['copyright'] = (bool) $this->readHeaderBSI(1);
 211
 212                 $thisfile_ac3_raw_bsi['original']  = (bool) $this->readHeaderBSI(1);
 213
 214                 $thisfile_ac3_raw_bsi['timecode1_flag'] = (bool) $this->readHeaderBSI(1);
 215                 if ($thisfile_ac3_raw_bsi['timecode1_flag']) {
 216                         $thisfile_ac3_raw_bsi['timecode1'] = $this->readHeaderBSI(14);
 217                 }
 218
 219                 $thisfile_ac3_raw_bsi['timecode2_flag'] = (bool) $this->readHeaderBSI(1);
 220                 if ($thisfile_ac3_raw_bsi['timecode2_flag']) {
 221                         $thisfile_ac3_raw_bsi['timecode2'] = $this->readHeaderBSI(14);
 222                 }
 223
 224                 $thisfile_ac3_raw_bsi['addbsi_flag'] = (bool) $this->readHeaderBSI(1);
 225                 if ($thisfile_ac3_raw_bsi['addbsi_flag']) {
 226                         $thisfile_ac3_raw_bsi['addbsi_length'] = $this->readHeaderBSI(6);
 227
 228                         $this->AC3header['bsi'] .= getid3_lib::BigEndian2Bin($this->fread($thisfile_ac3_raw_bsi['addbsi_length']));
 229
 230                         $thisfile_ac3_raw_bsi['addbsi_data'] = substr($this->AC3header['bsi'], $this->BSIoffset, $thisfile_ac3_raw_bsi['addbsi_length'] * 8);
 231                         $this->BSIoffset += $thisfile_ac3_raw_bsi['addbsi_length'] * 8;
 232                 }
 233
 234                 return true;
 235         }
 236
 237         private function readHeaderBSI($length) {
 238                 $data = substr($this->AC3header['bsi'], $this->BSIoffset, $length);
 239                 $this->BSIoffset += $length;
 240
 241                 return bindec($data);
 242         }
 243
 244         public static function sampleRateCodeLookup($fscod) {
 245                 static $sampleRateCodeLookup = array(
 246                         0 => 48000,
 247                         1 => 44100,
 248                         2 => 32000,
 249                         3 => 'reserved' // If the reserved code is indicated, the decoder should not attempt to decode audio and should mute.
 250                 );
 251                 return (isset($sampleRateCodeLookup[$fscod]) ? $sampleRateCodeLookup[$fscod] : false);
 252         }
 253
 254         public static function serviceTypeLookup($bsmod, $acmod) {
 255                 static $serviceTypeLookup = array();
 256                 if (empty($serviceTypeLookup)) {
 257                         for ($i = 0; $i <= 7; $i++) {
 258                                 $serviceTypeLookup[0][$i] = 'main audio service: complete main (CM)';
 259                                 $serviceTypeLookup[1][$i] = 'main audio service: music and effects (ME)';
 260                                 $serviceTypeLookup[2][$i] = 'associated service: visually impaired (VI)';
 261                                 $serviceTypeLookup[3][$i] = 'associated service: hearing impaired (HI)';
 262                                 $serviceTypeLookup[4][$i] = 'associated service: dialogue (D)';
 263                                 $serviceTypeLookup[5][$i] = 'associated service: commentary (C)';
 264                                 $serviceTypeLookup[6][$i] = 'associated service: emergency (E)';
 265                         }
 266
 267                         $serviceTypeLookup[7][1]      = 'associated service: voice over (VO)';
 268                         for ($i = 2; $i <= 7; $i++) {
 269                                 $serviceTypeLookup[7][$i] = 'main audio service: karaoke';
 270                         }
 271                 }
 272                 return (isset($serviceTypeLookup[$bsmod][$acmod]) ? $serviceTypeLookup[$bsmod][$acmod] : false);
 273         }
 274
 275         public static function audioCodingModeLookup($acmod) {
 276                 // array(channel configuration, # channels (not incl LFE), channel order)
 277                 static $audioCodingModeLookup = array (
 278                         0 => array('channel_config'=>'1+1', 'num_channels'=>2, 'channel_order'=>'Ch1,Ch2'),
 279                         1 => array('channel_config'=>'1/0', 'num_channels'=>1, 'channel_order'=>'C'),
 280                         2 => array('channel_config'=>'2/0', 'num_channels'=>2, 'channel_order'=>'L,R'),
 281                         3 => array('channel_config'=>'3/0', 'num_channels'=>3, 'channel_order'=>'L,C,R'),
 282                         4 => array('channel_config'=>'2/1', 'num_channels'=>3, 'channel_order'=>'L,R,S'),
 283                         5 => array('channel_config'=>'3/1', 'num_channels'=>4, 'channel_order'=>'L,C,R,S'),
 284                         6 => array('channel_config'=>'2/2', 'num_channels'=>4, 'channel_order'=>'L,R,SL,SR'),
 285                         7 => array('channel_config'=>'3/2', 'num_channels'=>5, 'channel_order'=>'L,C,R,SL,SR'),
 286                 );
 287                 return (isset($audioCodingModeLookup[$acmod]) ? $audioCodingModeLookup[$acmod] : false);
 288         }
 289
 290         public static function centerMixLevelLookup($cmixlev) {
 291                 static $centerMixLevelLookup;
 292                 if (empty($centerMixLevelLookup)) {
 293                         $centerMixLevelLookup = array(
 294                                 0 => pow(2, -3.0 / 6), // 0.707 (-3.0 dB)
 295                                 1 => pow(2, -4.5 / 6), // 0.595 (-4.5 dB)
 296                                 2 => pow(2, -6.0 / 6), // 0.500 (-6.0 dB)
 297                                 3 => 'reserved'
 298                         );
 299                 }
 300                 return (isset($centerMixLevelLookup[$cmixlev]) ? $centerMixLevelLookup[$cmixlev] : false);
 301         }
 302
 303         public static function surroundMixLevelLookup($surmixlev) {
 304                 static $surroundMixLevelLookup;
 305                 if (empty($surroundMixLevelLookup)) {
 306                         $surroundMixLevelLookup = array(
 307                                 0 => pow(2, -3.0 / 6),
 308                                 1 => pow(2, -6.0 / 6),
 309                                 2 => 0,
 310                                 3 => 'reserved'
 311                         );
 312                 }
 313                 return (isset($surroundMixLevelLookup[$surmixlev]) ? $surroundMixLevelLookup[$surmixlev] : false);
 314         }
 315
 316         public static function dolbySurroundModeLookup($dsurmod) {
 317                 static $dolbySurroundModeLookup = array(
 318                         0 => 'not indicated',
 319                         1 => 'Not Dolby Surround encoded',
 320                         2 => 'Dolby Surround encoded',
 321                         3 => 'reserved'
 322                 );
 323                 return (isset($dolbySurroundModeLookup[$dsurmod]) ? $dolbySurroundModeLookup[$dsurmod] : false);
 324         }
 325
 326         public static function channelsEnabledLookup($acmod, $lfeon) {
 327                 $lookup = array(
 328                         'ch1'=>(bool) ($acmod == 0),
 329                         'ch2'=>(bool) ($acmod == 0),
 330                         'left'=>(bool) ($acmod > 1),
 331                         'right'=>(bool) ($acmod > 1),
 332                         'center'=>(bool) ($acmod & 0x01),
 333                         'surround_mono'=>false,
 334                         'surround_left'=>false,
 335                         'surround_right'=>false,
 336                         'lfe'=>$lfeon);
 337                 switch ($acmod) {
 338                         case 4:
 339                         case 5:
 340                                 $lookup['surround_mono']  = true;
 341                                 break;
 342                         case 6:
 343                         case 7:
 344                                 $lookup['surround_left']  = true;
 345                                 $lookup['surround_right'] = true;
 346                                 break;
 347                 }
 348                 return $lookup;
 349         }
 350
 351         public static function heavyCompression($compre) {
 352                 // The first four bits indicate gain changes in 6.02dB increments which can be
 353                 // implemented with an arithmetic shift operation. The following four bits
 354                 // indicate linear gain changes, and require a 5-bit multiply.
 355                 // We will represent the two 4-bit fields of compr as follows:
 356                 //   X0 X1 X2 X3 . Y4 Y5 Y6 Y7
 357                 // The meaning of the X values is most simply described by considering X to represent a 4-bit
 358                 // signed integer with values from -8 to +7. The gain indicated by X is then (X + 1) * 6.02 dB. The
 359                 // following table shows this in detail.
 360
 361                 // Meaning of 4 msb of compr
 362                 //  7    +48.16 dB
 363                 //  6    +42.14 dB
 364                 //  5    +36.12 dB
 365                 //  4    +30.10 dB
 366                 //  3    +24.08 dB
 367                 //  2    +18.06 dB
 368                 //  1    +12.04 dB
 369                 //  0     +6.02 dB
 370                 // -1         0 dB
 371                 // -2     -6.02 dB
 372                 // -3    -12.04 dB
 373                 // -4    -18.06 dB
 374                 // -5    -24.08 dB
 375                 // -6    -30.10 dB
 376                 // -7    -36.12 dB
 377                 // -8    -42.14 dB
 378
 379                 $fourbit = str_pad(decbin(($compre & 0xF0) >> 4), 4, '0', STR_PAD_LEFT);
 380                 if ($fourbit{0} == '1') {
 381                         $log_gain = -8 + bindec(substr($fourbit, 1));
 382                 } else {
 383                         $log_gain = bindec(substr($fourbit, 1));
 384                 }
 385                 $log_gain = ($log_gain + 1) * getid3_lib::RGADamplitude2dB(2);
 386
 387                 // The value of Y is a linear representation of a gain change of up to -6 dB. Y is considered to
 388                 // be an unsigned fractional integer, with a leading value of 1, or: 0.1 Y4 Y5 Y6 Y7 (base 2). Y can
 389                 // represent values between 0.111112 (or 31/32) and 0.100002 (or 1/2). Thus, Y can represent gain
 390                 // changes from -0.28 dB to -6.02 dB.
 391
 392                 $lin_gain = (16 + ($compre & 0x0F)) / 32;
 393
 394                 // The combination of X and Y values allows compr to indicate gain changes from
 395                 //  48.16 - 0.28 = +47.89 dB, to
 396                 // -42.14 - 6.02 = -48.16 dB.
 397
 398                 return $log_gain - $lin_gain;
 399         }
 400
 401         public static function roomTypeLookup($roomtyp) {
 402                 static $roomTypeLookup = array(
 403                         0 => 'not indicated',
 404                         1 => 'large room, X curve monitor',
 405                         2 => 'small room, flat monitor',
 406                         3 => 'reserved'
 407                 );
 408                 return (isset($roomTypeLookup[$roomtyp]) ? $roomTypeLookup[$roomtyp] : false);
 409         }
 410
 411         public static function frameSizeLookup($frmsizecod, $fscod) {
 412                 $padding     = (bool) ($frmsizecod % 2);
 413                 $framesizeid =   floor($frmsizecod / 2);
 414
 415                 static $frameSizeLookup = array();
 416                 if (empty($frameSizeLookup)) {
 417                         $frameSizeLookup = array (
 418                                 0  => array(128, 138, 192),
 419                                 1  => array(40, 160, 174, 240),
 420                                 2  => array(48, 192, 208, 288),
 421                                 3  => array(56, 224, 242, 336),
 422                                 4  => array(64, 256, 278, 384),
 423                                 5  => array(80, 320, 348, 480),
 424                                 6  => array(96, 384, 416, 576),
 425                                 7  => array(112, 448, 486, 672),
 426                                 8  => array(128, 512, 556, 768),
 427                                 9  => array(160, 640, 696, 960),
 428                                 10 => array(192, 768, 834, 1152),
 429                                 11 => array(224, 896, 974, 1344),
 430                                 12 => array(256, 1024, 1114, 1536),
 431                                 13 => array(320, 1280, 1392, 1920),
 432                                 14 => array(384, 1536, 1670, 2304),
 433                                 15 => array(448, 1792, 1950, 2688),
 434                                 16 => array(512, 2048, 2228, 3072),
 435                                 17 => array(576, 2304, 2506, 3456),
 436                                 18 => array(640, 2560, 2786, 3840)
 437                         );
 438                 }
 439                 if (($fscod == 1) && $padding) {
 440                         // frame lengths are padded by 1 word (16 bits) at 44100
 441                         $frameSizeLookup[$frmsizecod] += 2;
 442                 }
 443                 return (isset($frameSizeLookup[$framesizeid][$fscod]) ? $frameSizeLookup[$framesizeid][$fscod] : false);
 444         }
 445
 446         public static function bitrateLookup($frmsizecod) {
 447                 $framesizeid =   floor($frmsizecod / 2);
 448
 449                 static $bitrateLookup = array(
 450                         0  => 32000,
 451                         1  => 40000,
 452                         2  => 48000,
 453                         3  => 56000,
 454                         4  => 64000,
 455                         5  => 80000,
 456                         6  => 96000,
 457                         7  => 112000,
 458                         8  => 128000,
 459                         9  => 160000,
 460                         10 => 192000,
 461                         11 => 224000,
 462                         12 => 256000,
 463                         13 => 320000,
 464                         14 => 384000,
 465                         15 => 448000,
 466                         16 => 512000,
 467                         17 => 576000,
 468                         18 => 640000
 469                 );
 470                 return (isset($bitrateLookup[$framesizeid]) ? $bitrateLookup[$framesizeid] : false);
 471         }
 472
 473
 474 }