[ Index ]

PHP Cross Reference of WordPress

title

Body

[close]

/wp-includes/ID3/ -> module.audio.ac3.php (source)

   1  <?php
   2  
   3  /////////////////////////////////////////////////////////////////
   4  /// getID3() by James Heinrich <info@getid3.org>               //
   5  //  available at https://github.com/JamesHeinrich/getID3       //
   6  //            or https://www.getid3.org                        //
   7  //            or http://getid3.sourceforge.net                 //
   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  if (!defined('GETID3_INCLUDEPATH')) { // prevent path-exposing attacks that access modules directly on public webservers
  18      exit;
  19  }
  20  
  21  class getid3_ac3 extends getid3_handler
  22  {
  23      /**
  24       * @var array
  25       */
  26      private $AC3header = array();
  27  
  28      /**
  29       * @var int
  30       */
  31      private $BSIoffset = 0;
  32  
  33      const syncword = 0x0B77;
  34  
  35      /**
  36       * @return bool
  37       */
  38  	public function Analyze() {
  39          $info = &$this->getid3->info;
  40  
  41          ///AH
  42          $info['ac3']['raw']['bsi'] = array();
  43          $thisfile_ac3              = &$info['ac3'];
  44          $thisfile_ac3_raw          = &$thisfile_ac3['raw'];
  45          $thisfile_ac3_raw_bsi      = &$thisfile_ac3_raw['bsi'];
  46  
  47  
  48          // http://www.atsc.org/standards/a_52a.pdf
  49  
  50          $info['fileformat'] = 'ac3';
  51  
  52          // An AC-3 serial coded audio bit stream is made up of a sequence of synchronization frames
  53          // Each synchronization frame contains 6 coded audio blocks (AB), each of which represent 256
  54          // new audio samples per channel. A synchronization information (SI) header at the beginning
  55          // of each frame contains information needed to acquire and maintain synchronization. A
  56          // bit stream information (BSI) header follows SI, and contains parameters describing the coded
  57          // audio service. The coded audio blocks may be followed by an auxiliary data (Aux) field. At the
  58          // end of each frame is an error check field that includes a CRC word for error detection. An
  59          // additional CRC word is located in the SI header, the use of which, by a decoder, is optional.
  60          //
  61          // syncinfo() | bsi() | AB0 | AB1 | AB2 | AB3 | AB4 | AB5 | Aux | CRC
  62  
  63          // syncinfo() {
  64          //      syncword    16
  65          //      crc1        16
  66          //      fscod        2
  67          //      frmsizecod   6
  68          // } /* end of syncinfo */
  69  
  70          $this->fseek($info['avdataoffset']);
  71          $tempAC3header = $this->fread(100); // should be enough to cover all data, there are some variable-length fields...?
  72          $this->AC3header['syncinfo']  =     getid3_lib::BigEndian2Int(substr($tempAC3header, 0, 2));
  73          $this->AC3header['bsi']       =     getid3_lib::BigEndian2Bin(substr($tempAC3header, 2));
  74          $thisfile_ac3_raw_bsi['bsid'] = (getid3_lib::LittleEndian2Int(substr($tempAC3header, 5, 1)) & 0xF8) >> 3; // AC3 and E-AC3 put the "bsid" version identifier in the same place, but unfortnately the 4 bytes between the syncword and the version identifier are interpreted differently, so grab it here so the following code structure can make sense
  75          unset($tempAC3header);
  76  
  77          if ($this->AC3header['syncinfo'] !== self::syncword) {
  78              if (!$this->isDependencyFor('matroska')) {
  79                  unset($info['fileformat'], $info['ac3']);
  80                  return $this->error('Expecting "'.dechex(self::syncword).'" at offset '.$info['avdataoffset'].', found "'.dechex($this->AC3header['syncinfo']).'"');
  81              }
  82          }
  83  
  84          $info['audio']['dataformat']   = 'ac3';
  85          $info['audio']['bitrate_mode'] = 'cbr';
  86          $info['audio']['lossless']     = false;
  87  
  88          if ($thisfile_ac3_raw_bsi['bsid'] <= 8) {
  89  
  90              $thisfile_ac3_raw_bsi['crc1']       = getid3_lib::Bin2Dec($this->readHeaderBSI(16));
  91              $thisfile_ac3_raw_bsi['fscod']      =                     $this->readHeaderBSI(2);   // 5.4.1.3
  92              $thisfile_ac3_raw_bsi['frmsizecod'] =                     $this->readHeaderBSI(6);   // 5.4.1.4
  93              if ($thisfile_ac3_raw_bsi['frmsizecod'] > 37) { // binary: 100101 - see Table 5.18 Frame Size Code Table (1 word = 16 bits)
  94                  $this->warning('Unexpected ac3.bsi.frmsizecod value: '.$thisfile_ac3_raw_bsi['frmsizecod'].', bitrate not set correctly');
  95              }
  96  
  97              $thisfile_ac3_raw_bsi['bsid']  = $this->readHeaderBSI(5); // we already know this from pre-parsing the version identifier, but re-read it to let the bitstream flow as intended
  98              $thisfile_ac3_raw_bsi['bsmod'] = $this->readHeaderBSI(3);
  99              $thisfile_ac3_raw_bsi['acmod'] = $this->readHeaderBSI(3);
 100  
 101              if ($thisfile_ac3_raw_bsi['acmod'] & 0x01) {
 102                  // If the lsb of acmod is a 1, center channel is in use and cmixlev follows in the bit stream.
 103                  $thisfile_ac3_raw_bsi['cmixlev'] = $this->readHeaderBSI(2);
 104                  $thisfile_ac3['center_mix_level'] = self::centerMixLevelLookup($thisfile_ac3_raw_bsi['cmixlev']);
 105              }
 106  
 107              if ($thisfile_ac3_raw_bsi['acmod'] & 0x04) {
 108                  // If the msb of acmod is a 1, surround channels are in use and surmixlev follows in the bit stream.
 109                  $thisfile_ac3_raw_bsi['surmixlev'] = $this->readHeaderBSI(2);
 110                  $thisfile_ac3['surround_mix_level'] = self::surroundMixLevelLookup($thisfile_ac3_raw_bsi['surmixlev']);
 111              }
 112  
 113              if ($thisfile_ac3_raw_bsi['acmod'] == 0x02) {
 114                  // When operating in the two channel mode, this 2-bit code indicates whether or not the program has been encoded in Dolby Surround.
 115                  $thisfile_ac3_raw_bsi['dsurmod'] = $this->readHeaderBSI(2);
 116                  $thisfile_ac3['dolby_surround_mode'] = self::dolbySurroundModeLookup($thisfile_ac3_raw_bsi['dsurmod']);
 117              }
 118  
 119              $thisfile_ac3_raw_bsi['flags']['lfeon'] = (bool) $this->readHeaderBSI(1);
 120  
 121              // This indicates how far the average dialogue level is below digital 100 percent. Valid values are 1-31.
 122              // 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.
 123              $thisfile_ac3_raw_bsi['dialnorm'] = $this->readHeaderBSI(5);                 // 5.4.2.8 dialnorm: Dialogue Normalization, 5 Bits
 124  
 125              $thisfile_ac3_raw_bsi['flags']['compr'] = (bool) $this->readHeaderBSI(1);       // 5.4.2.9 compre: Compression Gain Word Exists, 1 Bit
 126              if ($thisfile_ac3_raw_bsi['flags']['compr']) {
 127                  $thisfile_ac3_raw_bsi['compr'] = $this->readHeaderBSI(8);                // 5.4.2.10 compr: Compression Gain Word, 8 Bits
 128                  $thisfile_ac3['heavy_compression'] = self::heavyCompression($thisfile_ac3_raw_bsi['compr']);
 129              }
 130  
 131              $thisfile_ac3_raw_bsi['flags']['langcod'] = (bool) $this->readHeaderBSI(1);     // 5.4.2.11 langcode: Language Code Exists, 1 Bit
 132              if ($thisfile_ac3_raw_bsi['flags']['langcod']) {
 133                  $thisfile_ac3_raw_bsi['langcod'] = $this->readHeaderBSI(8);              // 5.4.2.12 langcod: Language Code, 8 Bits
 134              }
 135  
 136              $thisfile_ac3_raw_bsi['flags']['audprodinfo'] = (bool) $this->readHeaderBSI(1);  // 5.4.2.13 audprodie: Audio Production Information Exists, 1 Bit
 137              if ($thisfile_ac3_raw_bsi['flags']['audprodinfo']) {
 138                  $thisfile_ac3_raw_bsi['mixlevel'] = $this->readHeaderBSI(5);             // 5.4.2.14 mixlevel: Mixing Level, 5 Bits
 139                  $thisfile_ac3_raw_bsi['roomtyp']  = $this->readHeaderBSI(2);             // 5.4.2.15 roomtyp: Room Type, 2 Bits
 140  
 141                  $thisfile_ac3['mixing_level'] = (80 + $thisfile_ac3_raw_bsi['mixlevel']).'dB';
 142                  $thisfile_ac3['room_type']    = self::roomTypeLookup($thisfile_ac3_raw_bsi['roomtyp']);
 143              }
 144  
 145  
 146              $thisfile_ac3_raw_bsi['dialnorm2'] = $this->readHeaderBSI(5);                // 5.4.2.16 dialnorm2: Dialogue Normalization, ch2, 5 Bits
 147              $thisfile_ac3['dialogue_normalization2'] = '-'.$thisfile_ac3_raw_bsi['dialnorm2'].'dB';  // This indicates how far the average dialogue level is below digital 100 percent. Valid values are 1-31. 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.
 148  
 149              $thisfile_ac3_raw_bsi['flags']['compr2'] = (bool) $this->readHeaderBSI(1);       // 5.4.2.17 compr2e: Compression Gain Word Exists, ch2, 1 Bit
 150              if ($thisfile_ac3_raw_bsi['flags']['compr2']) {
 151                  $thisfile_ac3_raw_bsi['compr2'] = $this->readHeaderBSI(8);               // 5.4.2.18 compr2: Compression Gain Word, ch2, 8 Bits
 152                  $thisfile_ac3['heavy_compression2'] = self::heavyCompression($thisfile_ac3_raw_bsi['compr2']);
 153              }
 154  
 155              $thisfile_ac3_raw_bsi['flags']['langcod2'] = (bool) $this->readHeaderBSI(1);    // 5.4.2.19 langcod2e: Language Code Exists, ch2, 1 Bit
 156              if ($thisfile_ac3_raw_bsi['flags']['langcod2']) {
 157                  $thisfile_ac3_raw_bsi['langcod2'] = $this->readHeaderBSI(8);             // 5.4.2.20 langcod2: Language Code, ch2, 8 Bits
 158              }
 159  
 160              $thisfile_ac3_raw_bsi['flags']['audprodinfo2'] = (bool) $this->readHeaderBSI(1); // 5.4.2.21 audprodi2e: Audio Production Information Exists, ch2, 1 Bit
 161              if ($thisfile_ac3_raw_bsi['flags']['audprodinfo2']) {
 162                  $thisfile_ac3_raw_bsi['mixlevel2'] = $this->readHeaderBSI(5);            // 5.4.2.22 mixlevel2: Mixing Level, ch2, 5 Bits
 163                  $thisfile_ac3_raw_bsi['roomtyp2']  = $this->readHeaderBSI(2);            // 5.4.2.23 roomtyp2: Room Type, ch2, 2 Bits
 164  
 165                  $thisfile_ac3['mixing_level2'] = (80 + $thisfile_ac3_raw_bsi['mixlevel2']).'dB';
 166                  $thisfile_ac3['room_type2']    = self::roomTypeLookup($thisfile_ac3_raw_bsi['roomtyp2']);
 167              }
 168  
 169              $thisfile_ac3_raw_bsi['copyright'] = (bool) $this->readHeaderBSI(1);         // 5.4.2.24 copyrightb: Copyright Bit, 1 Bit
 170  
 171              $thisfile_ac3_raw_bsi['original']  = (bool) $this->readHeaderBSI(1);         // 5.4.2.25 origbs: Original Bit Stream, 1 Bit
 172  
 173              $thisfile_ac3_raw_bsi['flags']['timecod1'] = $this->readHeaderBSI(2);            // 5.4.2.26 timecod1e, timcode2e: Time Code (first and second) Halves Exist, 2 Bits
 174              if ($thisfile_ac3_raw_bsi['flags']['timecod1'] & 0x01) {
 175                  $thisfile_ac3_raw_bsi['timecod1'] = $this->readHeaderBSI(14);            // 5.4.2.27 timecod1: Time code first half, 14 bits
 176                  $thisfile_ac3['timecode1'] = 0;
 177                  $thisfile_ac3['timecode1'] += (($thisfile_ac3_raw_bsi['timecod1'] & 0x3E00) >>  9) * 3600;  // The first 5 bits of this 14-bit field represent the time in hours, with valid values of 0�23
 178                  $thisfile_ac3['timecode1'] += (($thisfile_ac3_raw_bsi['timecod1'] & 0x01F8) >>  3) *   60;  // The next 6 bits represent the time in minutes, with valid values of 0�59
 179                  $thisfile_ac3['timecode1'] += (($thisfile_ac3_raw_bsi['timecod1'] & 0x0003) >>  0) *    8;  // The final 3 bits represents the time in 8 second increments, with valid values of 0�7 (representing 0, 8, 16, ... 56 seconds)
 180              }
 181              if ($thisfile_ac3_raw_bsi['flags']['timecod1'] & 0x02) {
 182                  $thisfile_ac3_raw_bsi['timecod2'] = $this->readHeaderBSI(14);            // 5.4.2.28 timecod2: Time code second half, 14 bits
 183                  $thisfile_ac3['timecode2'] = 0;
 184                  $thisfile_ac3['timecode2'] += (($thisfile_ac3_raw_bsi['timecod2'] & 0x3800) >> 11) *   1;              // The first 3 bits of this 14-bit field represent the time in seconds, with valid values from 0�7 (representing 0-7 seconds)
 185                  $thisfile_ac3['timecode2'] += (($thisfile_ac3_raw_bsi['timecod2'] & 0x07C0) >>  6) *  (1 / 30);        // The next 5 bits represents the time in frames, with valid values from 0�29 (one frame = 1/30th of a second)
 186                  $thisfile_ac3['timecode2'] += (($thisfile_ac3_raw_bsi['timecod2'] & 0x003F) >>  0) * ((1 / 30) / 60);  // The final 6 bits represents fractions of 1/64 of a frame, with valid values from 0�63
 187              }
 188  
 189              $thisfile_ac3_raw_bsi['flags']['addbsi'] = (bool) $this->readHeaderBSI(1);
 190              if ($thisfile_ac3_raw_bsi['flags']['addbsi']) {
 191                  $thisfile_ac3_raw_bsi['addbsi_length'] = $this->readHeaderBSI(6) + 1; // This 6-bit code, which exists only if addbside is a 1, indicates the length in bytes of additional bit stream information. The valid range of addbsil is 0�63, indicating 1�64 additional bytes, respectively.
 192  
 193                  $this->AC3header['bsi'] .= getid3_lib::BigEndian2Bin($this->fread($thisfile_ac3_raw_bsi['addbsi_length']));
 194  
 195                  $thisfile_ac3_raw_bsi['addbsi_data'] = substr($this->AC3header['bsi'], $this->BSIoffset, $thisfile_ac3_raw_bsi['addbsi_length'] * 8);
 196                  $this->BSIoffset += $thisfile_ac3_raw_bsi['addbsi_length'] * 8;
 197              }
 198  
 199  
 200          } elseif ($thisfile_ac3_raw_bsi['bsid'] <= 16) { // E-AC3
 201  
 202  
 203              $this->error('E-AC3 parsing is incomplete and experimental in this version of getID3 ('.$this->getid3->version().'). Notably the bitrate calculations are wrong -- value might (or not) be correct, but it is not calculated correctly. Email info@getid3.org if you know how to calculate EAC3 bitrate correctly.');
 204              $info['audio']['dataformat'] = 'eac3';
 205  
 206              $thisfile_ac3_raw_bsi['strmtyp']          =        $this->readHeaderBSI(2);
 207              $thisfile_ac3_raw_bsi['substreamid']      =        $this->readHeaderBSI(3);
 208              $thisfile_ac3_raw_bsi['frmsiz']           =        $this->readHeaderBSI(11);
 209              $thisfile_ac3_raw_bsi['fscod']            =        $this->readHeaderBSI(2);
 210              if ($thisfile_ac3_raw_bsi['fscod'] == 3) {
 211                  $thisfile_ac3_raw_bsi['fscod2']       =        $this->readHeaderBSI(2);
 212                  $thisfile_ac3_raw_bsi['numblkscod'] = 3; // six blocks per syncframe
 213              } else {
 214                  $thisfile_ac3_raw_bsi['numblkscod']   =        $this->readHeaderBSI(2);
 215              }
 216              $thisfile_ac3['bsi']['blocks_per_sync_frame'] = self::blocksPerSyncFrame($thisfile_ac3_raw_bsi['numblkscod']);
 217              $thisfile_ac3_raw_bsi['acmod']            =        $this->readHeaderBSI(3);
 218              $thisfile_ac3_raw_bsi['flags']['lfeon']   = (bool) $this->readHeaderBSI(1);
 219              $thisfile_ac3_raw_bsi['bsid']             =        $this->readHeaderBSI(5); // we already know this from pre-parsing the version identifier, but re-read it to let the bitstream flow as intended
 220              $thisfile_ac3_raw_bsi['dialnorm']         =        $this->readHeaderBSI(5);
 221              $thisfile_ac3_raw_bsi['flags']['compr']       = (bool) $this->readHeaderBSI(1);
 222              if ($thisfile_ac3_raw_bsi['flags']['compr']) {
 223                  $thisfile_ac3_raw_bsi['compr']        =        $this->readHeaderBSI(8);
 224              }
 225              if ($thisfile_ac3_raw_bsi['acmod'] == 0) { // if 1+1 mode (dual mono, so some items need a second value)
 226                  $thisfile_ac3_raw_bsi['dialnorm2']    =        $this->readHeaderBSI(5);
 227                  $thisfile_ac3_raw_bsi['flags']['compr2']  = (bool) $this->readHeaderBSI(1);
 228                  if ($thisfile_ac3_raw_bsi['flags']['compr2']) {
 229                      $thisfile_ac3_raw_bsi['compr2']   =        $this->readHeaderBSI(8);
 230                  }
 231              }
 232              if ($thisfile_ac3_raw_bsi['strmtyp'] == 1) { // if dependent stream
 233                  $thisfile_ac3_raw_bsi['flags']['chanmap'] = (bool) $this->readHeaderBSI(1);
 234                  if ($thisfile_ac3_raw_bsi['flags']['chanmap']) {
 235                      $thisfile_ac3_raw_bsi['chanmap']  =        $this->readHeaderBSI(8);
 236                  }
 237              }
 238              $thisfile_ac3_raw_bsi['flags']['mixmdat']     = (bool) $this->readHeaderBSI(1);
 239              if ($thisfile_ac3_raw_bsi['flags']['mixmdat']) { // Mixing metadata
 240                  if ($thisfile_ac3_raw_bsi['acmod'] > 2) { // if more than 2 channels
 241                      $thisfile_ac3_raw_bsi['dmixmod']  =        $this->readHeaderBSI(2);
 242                  }
 243                  if (($thisfile_ac3_raw_bsi['acmod'] & 0x01) && ($thisfile_ac3_raw_bsi['acmod'] > 2)) { // if three front channels exist
 244                      $thisfile_ac3_raw_bsi['ltrtcmixlev'] =        $this->readHeaderBSI(3);
 245                      $thisfile_ac3_raw_bsi['lorocmixlev'] =        $this->readHeaderBSI(3);
 246                  }
 247                  if ($thisfile_ac3_raw_bsi['acmod'] & 0x04) { // if a surround channel exists
 248                      $thisfile_ac3_raw_bsi['ltrtsurmixlev'] =        $this->readHeaderBSI(3);
 249                      $thisfile_ac3_raw_bsi['lorosurmixlev'] =        $this->readHeaderBSI(3);
 250                  }
 251                  if ($thisfile_ac3_raw_bsi['flags']['lfeon']) { // if the LFE channel exists
 252                      $thisfile_ac3_raw_bsi['flags']['lfemixlevcod'] = (bool) $this->readHeaderBSI(1);
 253                      if ($thisfile_ac3_raw_bsi['flags']['lfemixlevcod']) {
 254                          $thisfile_ac3_raw_bsi['lfemixlevcod']  =        $this->readHeaderBSI(5);
 255                      }
 256                  }
 257                  if ($thisfile_ac3_raw_bsi['strmtyp'] == 0) { // if independent stream
 258                      $thisfile_ac3_raw_bsi['flags']['pgmscl'] = (bool) $this->readHeaderBSI(1);
 259                      if ($thisfile_ac3_raw_bsi['flags']['pgmscl']) {
 260                          $thisfile_ac3_raw_bsi['pgmscl']  =        $this->readHeaderBSI(6);
 261                      }
 262                      if ($thisfile_ac3_raw_bsi['acmod'] == 0) { // if 1+1 mode (dual mono, so some items need a second value)
 263                          $thisfile_ac3_raw_bsi['flags']['pgmscl2'] = (bool) $this->readHeaderBSI(1);
 264                          if ($thisfile_ac3_raw_bsi['flags']['pgmscl2']) {
 265                              $thisfile_ac3_raw_bsi['pgmscl2']  =        $this->readHeaderBSI(6);
 266                          }
 267                      }
 268                      $thisfile_ac3_raw_bsi['flags']['extpgmscl'] = (bool) $this->readHeaderBSI(1);
 269                      if ($thisfile_ac3_raw_bsi['flags']['extpgmscl']) {
 270                          $thisfile_ac3_raw_bsi['extpgmscl']  =        $this->readHeaderBSI(6);
 271                      }
 272                      $thisfile_ac3_raw_bsi['mixdef']  =        $this->readHeaderBSI(2);
 273                      if ($thisfile_ac3_raw_bsi['mixdef'] == 1) { // mixing option 2
 274                          $thisfile_ac3_raw_bsi['premixcmpsel']  = (bool) $this->readHeaderBSI(1);
 275                          $thisfile_ac3_raw_bsi['drcsrc']        = (bool) $this->readHeaderBSI(1);
 276                          $thisfile_ac3_raw_bsi['premixcmpscl']  =        $this->readHeaderBSI(3);
 277                      } elseif ($thisfile_ac3_raw_bsi['mixdef'] == 2) { // mixing option 3
 278                          $thisfile_ac3_raw_bsi['mixdata']       =        $this->readHeaderBSI(12);
 279                      } elseif ($thisfile_ac3_raw_bsi['mixdef'] == 3) { // mixing option 4
 280                          $mixdefbitsread = 0;
 281                          $thisfile_ac3_raw_bsi['mixdeflen']     =        $this->readHeaderBSI(5); $mixdefbitsread += 5;
 282                          $thisfile_ac3_raw_bsi['flags']['mixdata2'] = (bool) $this->readHeaderBSI(1); $mixdefbitsread += 1;
 283                          if ($thisfile_ac3_raw_bsi['flags']['mixdata2']) {
 284                              $thisfile_ac3_raw_bsi['premixcmpsel']  = (bool) $this->readHeaderBSI(1); $mixdefbitsread += 1;
 285                              $thisfile_ac3_raw_bsi['drcsrc']        = (bool) $this->readHeaderBSI(1); $mixdefbitsread += 1;
 286                              $thisfile_ac3_raw_bsi['premixcmpscl']  =        $this->readHeaderBSI(3); $mixdefbitsread += 3;
 287                              $thisfile_ac3_raw_bsi['flags']['extpgmlscl']   = (bool) $this->readHeaderBSI(1); $mixdefbitsread += 1;
 288                              if ($thisfile_ac3_raw_bsi['flags']['extpgmlscl']) {
 289                                  $thisfile_ac3_raw_bsi['extpgmlscl']    =        $this->readHeaderBSI(4); $mixdefbitsread += 4;
 290                              }
 291                              $thisfile_ac3_raw_bsi['flags']['extpgmcscl']   = (bool) $this->readHeaderBSI(1); $mixdefbitsread += 1;
 292                              if ($thisfile_ac3_raw_bsi['flags']['extpgmcscl']) {
 293                                  $thisfile_ac3_raw_bsi['extpgmcscl']    =        $this->readHeaderBSI(4); $mixdefbitsread += 4;
 294                              }
 295                              $thisfile_ac3_raw_bsi['flags']['extpgmrscl']   = (bool) $this->readHeaderBSI(1); $mixdefbitsread += 1;
 296                              if ($thisfile_ac3_raw_bsi['flags']['extpgmrscl']) {
 297                                  $thisfile_ac3_raw_bsi['extpgmrscl']    =        $this->readHeaderBSI(4);
 298                              }
 299                              $thisfile_ac3_raw_bsi['flags']['extpgmlsscl']  = (bool) $this->readHeaderBSI(1); $mixdefbitsread += 1;
 300                              if ($thisfile_ac3_raw_bsi['flags']['extpgmlsscl']) {
 301                                  $thisfile_ac3_raw_bsi['extpgmlsscl']   =        $this->readHeaderBSI(4); $mixdefbitsread += 4;
 302                              }
 303                              $thisfile_ac3_raw_bsi['flags']['extpgmrsscl']  = (bool) $this->readHeaderBSI(1); $mixdefbitsread += 1;
 304                              if ($thisfile_ac3_raw_bsi['flags']['extpgmrsscl']) {
 305                                  $thisfile_ac3_raw_bsi['extpgmrsscl']   =        $this->readHeaderBSI(4); $mixdefbitsread += 4;
 306                              }
 307                              $thisfile_ac3_raw_bsi['flags']['extpgmlfescl'] = (bool) $this->readHeaderBSI(1); $mixdefbitsread += 1;
 308                              if ($thisfile_ac3_raw_bsi['flags']['extpgmlfescl']) {
 309                                  $thisfile_ac3_raw_bsi['extpgmlfescl']  =        $this->readHeaderBSI(4); $mixdefbitsread += 4;
 310                              }
 311                              $thisfile_ac3_raw_bsi['flags']['dmixscl']      = (bool) $this->readHeaderBSI(1); $mixdefbitsread += 1;
 312                              if ($thisfile_ac3_raw_bsi['flags']['dmixscl']) {
 313                                  $thisfile_ac3_raw_bsi['dmixscl']       =        $this->readHeaderBSI(4); $mixdefbitsread += 4;
 314                              }
 315                              $thisfile_ac3_raw_bsi['flags']['addch']        = (bool) $this->readHeaderBSI(1); $mixdefbitsread += 1;
 316                              if ($thisfile_ac3_raw_bsi['flags']['addch']) {
 317                                  $thisfile_ac3_raw_bsi['flags']['extpgmaux1scl']   = (bool) $this->readHeaderBSI(1); $mixdefbitsread += 1;
 318                                  if ($thisfile_ac3_raw_bsi['flags']['extpgmaux1scl']) {
 319                                      $thisfile_ac3_raw_bsi['extpgmaux1scl']    =        $this->readHeaderBSI(4); $mixdefbitsread += 4;
 320                                  }
 321                                  $thisfile_ac3_raw_bsi['flags']['extpgmaux2scl']   = (bool) $this->readHeaderBSI(1); $mixdefbitsread += 1;
 322                                  if ($thisfile_ac3_raw_bsi['flags']['extpgmaux2scl']) {
 323                                      $thisfile_ac3_raw_bsi['extpgmaux2scl']    =        $this->readHeaderBSI(4); $mixdefbitsread += 4;
 324                                  }
 325                              }
 326                          }
 327                          $thisfile_ac3_raw_bsi['flags']['mixdata3'] = (bool) $this->readHeaderBSI(1); $mixdefbitsread += 1;
 328                          if ($thisfile_ac3_raw_bsi['flags']['mixdata3']) {
 329                              $thisfile_ac3_raw_bsi['spchdat']   =        $this->readHeaderBSI(5); $mixdefbitsread += 5;
 330                              $thisfile_ac3_raw_bsi['flags']['addspchdat'] = (bool) $this->readHeaderBSI(1); $mixdefbitsread += 1;
 331                              if ($thisfile_ac3_raw_bsi['flags']['addspchdat']) {
 332                                  $thisfile_ac3_raw_bsi['spchdat1']   =         $this->readHeaderBSI(5); $mixdefbitsread += 5;
 333                                  $thisfile_ac3_raw_bsi['spchan1att'] =         $this->readHeaderBSI(2); $mixdefbitsread += 2;
 334                                  $thisfile_ac3_raw_bsi['flags']['addspchdat1'] = (bool) $this->readHeaderBSI(1); $mixdefbitsread += 1;
 335                                  if ($thisfile_ac3_raw_bsi['flags']['addspchdat1']) {
 336                                      $thisfile_ac3_raw_bsi['spchdat2']   =         $this->readHeaderBSI(5); $mixdefbitsread += 5;
 337                                      $thisfile_ac3_raw_bsi['spchan2att'] =         $this->readHeaderBSI(3); $mixdefbitsread += 3;
 338                                  }
 339                              }
 340                          }
 341                          $mixdata_bits = (8 * ($thisfile_ac3_raw_bsi['mixdeflen'] + 2)) - $mixdefbitsread;
 342                          $mixdata_fill = (($mixdata_bits % 8) ? 8 - ($mixdata_bits % 8) : 0);
 343                          $thisfile_ac3_raw_bsi['mixdata']     =        $this->readHeaderBSI($mixdata_bits);
 344                          $thisfile_ac3_raw_bsi['mixdatafill'] =        $this->readHeaderBSI($mixdata_fill);
 345                          unset($mixdefbitsread, $mixdata_bits, $mixdata_fill);
 346                      }
 347                      if ($thisfile_ac3_raw_bsi['acmod'] < 2) { // if mono or dual mono source
 348                          $thisfile_ac3_raw_bsi['flags']['paninfo'] = (bool) $this->readHeaderBSI(1);
 349                          if ($thisfile_ac3_raw_bsi['flags']['paninfo']) {
 350                              $thisfile_ac3_raw_bsi['panmean']   =        $this->readHeaderBSI(8);
 351                              $thisfile_ac3_raw_bsi['paninfo']   =        $this->readHeaderBSI(6);
 352                          }
 353                          if ($thisfile_ac3_raw_bsi['acmod'] == 0) { // if 1+1 mode (dual mono, so some items need a second value)
 354                              $thisfile_ac3_raw_bsi['flags']['paninfo2'] = (bool) $this->readHeaderBSI(1);
 355                              if ($thisfile_ac3_raw_bsi['flags']['paninfo2']) {
 356                                  $thisfile_ac3_raw_bsi['panmean2']   =        $this->readHeaderBSI(8);
 357                                  $thisfile_ac3_raw_bsi['paninfo2']   =        $this->readHeaderBSI(6);
 358                              }
 359                          }
 360                      }
 361                      $thisfile_ac3_raw_bsi['flags']['frmmixcfginfo'] = (bool) $this->readHeaderBSI(1);
 362                      if ($thisfile_ac3_raw_bsi['flags']['frmmixcfginfo']) { // mixing configuration information
 363                          if ($thisfile_ac3_raw_bsi['numblkscod'] == 0) {
 364                              $thisfile_ac3_raw_bsi['blkmixcfginfo'][0]  =        $this->readHeaderBSI(5);
 365                          } else {
 366                              for ($blk = 0; $blk < $thisfile_ac3_raw_bsi['numblkscod']; $blk++) {
 367                                  $thisfile_ac3_raw_bsi['flags']['blkmixcfginfo'.$blk] = (bool) $this->readHeaderBSI(1);
 368                                  if ($thisfile_ac3_raw_bsi['flags']['blkmixcfginfo'.$blk]) { // mixing configuration information
 369                                      $thisfile_ac3_raw_bsi['blkmixcfginfo'][$blk]  =        $this->readHeaderBSI(5);
 370                                  }
 371                              }
 372                          }
 373                      }
 374                  }
 375              }
 376              $thisfile_ac3_raw_bsi['flags']['infomdat']          = (bool) $this->readHeaderBSI(1);
 377              if ($thisfile_ac3_raw_bsi['flags']['infomdat']) { // Informational metadata
 378                  $thisfile_ac3_raw_bsi['bsmod']                  =        $this->readHeaderBSI(3);
 379                  $thisfile_ac3_raw_bsi['flags']['copyrightb']    = (bool) $this->readHeaderBSI(1);
 380                  $thisfile_ac3_raw_bsi['flags']['origbs']        = (bool) $this->readHeaderBSI(1);
 381                  if ($thisfile_ac3_raw_bsi['acmod'] == 2) { //  if in 2/0 mode
 382                      $thisfile_ac3_raw_bsi['dsurmod']            =        $this->readHeaderBSI(2);
 383                      $thisfile_ac3_raw_bsi['dheadphonmod']       =        $this->readHeaderBSI(2);
 384                  }
 385                  if ($thisfile_ac3_raw_bsi['acmod'] >= 6) { //  if both surround channels exist
 386                      $thisfile_ac3_raw_bsi['dsurexmod']          =        $this->readHeaderBSI(2);
 387                  }
 388                  $thisfile_ac3_raw_bsi['flags']['audprodi']      = (bool) $this->readHeaderBSI(1);
 389                  if ($thisfile_ac3_raw_bsi['flags']['audprodi']) {
 390                      $thisfile_ac3_raw_bsi['mixlevel']           =        $this->readHeaderBSI(5);
 391                      $thisfile_ac3_raw_bsi['roomtyp']            =        $this->readHeaderBSI(2);
 392                      $thisfile_ac3_raw_bsi['flags']['adconvtyp'] = (bool) $this->readHeaderBSI(1);
 393                  }
 394                  if ($thisfile_ac3_raw_bsi['acmod'] == 0) { //  if 1+1 mode (dual mono, so some items need a second value)
 395                      $thisfile_ac3_raw_bsi['flags']['audprodi2']      = (bool) $this->readHeaderBSI(1);
 396                      if ($thisfile_ac3_raw_bsi['flags']['audprodi2']) {
 397                          $thisfile_ac3_raw_bsi['mixlevel2']           =        $this->readHeaderBSI(5);
 398                          $thisfile_ac3_raw_bsi['roomtyp2']            =        $this->readHeaderBSI(2);
 399                          $thisfile_ac3_raw_bsi['flags']['adconvtyp2'] = (bool) $this->readHeaderBSI(1);
 400                      }
 401                  }
 402                  if ($thisfile_ac3_raw_bsi['fscod'] < 3) { // if not half sample rate
 403                      $thisfile_ac3_raw_bsi['flags']['sourcefscod'] = (bool) $this->readHeaderBSI(1);
 404                  }
 405              }
 406              if (($thisfile_ac3_raw_bsi['strmtyp'] == 0) && ($thisfile_ac3_raw_bsi['numblkscod'] != 3)) { //  if both surround channels exist
 407                  $thisfile_ac3_raw_bsi['flags']['convsync'] = (bool) $this->readHeaderBSI(1);
 408              }
 409              if ($thisfile_ac3_raw_bsi['strmtyp'] == 2) { //  if bit stream converted from AC-3
 410                  if ($thisfile_ac3_raw_bsi['numblkscod'] != 3) { // 6 blocks per syncframe
 411                      $thisfile_ac3_raw_bsi['flags']['blkid']  = 1;
 412                  } else {
 413                      $thisfile_ac3_raw_bsi['flags']['blkid']  = (bool) $this->readHeaderBSI(1);
 414                  }
 415                  if ($thisfile_ac3_raw_bsi['flags']['blkid']) {
 416                      $thisfile_ac3_raw_bsi['frmsizecod']  =        $this->readHeaderBSI(6);
 417                  }
 418              }
 419              $thisfile_ac3_raw_bsi['flags']['addbsi']  = (bool) $this->readHeaderBSI(1);
 420              if ($thisfile_ac3_raw_bsi['flags']['addbsi']) {
 421                  $thisfile_ac3_raw_bsi['addbsil']  =        $this->readHeaderBSI(6);
 422                  $thisfile_ac3_raw_bsi['addbsi']   =        $this->readHeaderBSI(($thisfile_ac3_raw_bsi['addbsil'] + 1) * 8);
 423              }
 424  
 425          } else {
 426  
 427              $this->error('Bit stream identification is version '.$thisfile_ac3_raw_bsi['bsid'].', but getID3() only understands up to version 16. Please submit a support ticket with a sample file.');
 428              unset($info['ac3']);
 429              return false;
 430  
 431          }
 432  
 433          if (isset($thisfile_ac3_raw_bsi['fscod2'])) {
 434              $thisfile_ac3['sample_rate'] = self::sampleRateCodeLookup2($thisfile_ac3_raw_bsi['fscod2']);
 435          } else {
 436              $thisfile_ac3['sample_rate'] = self::sampleRateCodeLookup($thisfile_ac3_raw_bsi['fscod']);
 437          }
 438          if ($thisfile_ac3_raw_bsi['fscod'] <= 3) {
 439              $info['audio']['sample_rate'] = $thisfile_ac3['sample_rate'];
 440          } else {
 441              $this->warning('Unexpected ac3.bsi.fscod value: '.$thisfile_ac3_raw_bsi['fscod']);
 442          }
 443          if (isset($thisfile_ac3_raw_bsi['frmsizecod'])) {
 444              $thisfile_ac3['frame_length'] = self::frameSizeLookup($thisfile_ac3_raw_bsi['frmsizecod'], $thisfile_ac3_raw_bsi['fscod']);
 445              $thisfile_ac3['bitrate']      = self::bitrateLookup($thisfile_ac3_raw_bsi['frmsizecod']);
 446          } elseif (!empty($thisfile_ac3_raw_bsi['frmsiz'])) {
 447              // this isn't right, but it's (usually) close, roughly 5% less than it should be.
 448              // but WHERE is the actual bitrate value stored in EAC3?? email info@getid3.org if you know!
 449              $thisfile_ac3['bitrate']      = ($thisfile_ac3_raw_bsi['frmsiz'] + 1) * 16 * 30; // The frmsiz field shall contain a value one less than the overall size of the coded syncframe in 16-bit words. That is, this field may assume a value ranging from 0 to 2047, and these values correspond to syncframe sizes ranging from 1 to 2048.
 450              // kludge-fix to make it approximately the expected value, still not "right":
 451              $thisfile_ac3['bitrate'] = round(($thisfile_ac3['bitrate'] * 1.05) / 16000) * 16000;
 452          }
 453          $info['audio']['bitrate'] = $thisfile_ac3['bitrate'];
 454  
 455          if (isset($thisfile_ac3_raw_bsi['bsmod']) && isset($thisfile_ac3_raw_bsi['acmod'])) {
 456              $thisfile_ac3['service_type'] = self::serviceTypeLookup($thisfile_ac3_raw_bsi['bsmod'], $thisfile_ac3_raw_bsi['acmod']);
 457          }
 458          $ac3_coding_mode = self::audioCodingModeLookup($thisfile_ac3_raw_bsi['acmod']);
 459          foreach($ac3_coding_mode as $key => $value) {
 460              $thisfile_ac3[$key] = $value;
 461          }
 462          switch ($thisfile_ac3_raw_bsi['acmod']) {
 463              case 0:
 464              case 1:
 465                  $info['audio']['channelmode'] = 'mono';
 466                  break;
 467              case 3:
 468              case 4:
 469                  $info['audio']['channelmode'] = 'stereo';
 470                  break;
 471              default:
 472                  $info['audio']['channelmode'] = 'surround';
 473                  break;
 474          }
 475          $info['audio']['channels'] = $thisfile_ac3['num_channels'];
 476  
 477          $thisfile_ac3['lfe_enabled'] = $thisfile_ac3_raw_bsi['flags']['lfeon'];
 478          if ($thisfile_ac3_raw_bsi['flags']['lfeon']) {
 479              $info['audio']['channels'] .= '.1';
 480          }
 481  
 482          $thisfile_ac3['channels_enabled'] = self::channelsEnabledLookup($thisfile_ac3_raw_bsi['acmod'], $thisfile_ac3_raw_bsi['flags']['lfeon']);
 483          $thisfile_ac3['dialogue_normalization'] = '-'.$thisfile_ac3_raw_bsi['dialnorm'].'dB';
 484  
 485          return true;
 486      }
 487  
 488      /**
 489       * @param int $length
 490       *
 491       * @return int
 492       */
 493  	private function readHeaderBSI($length) {
 494          $data = substr($this->AC3header['bsi'], $this->BSIoffset, $length);
 495          $this->BSIoffset += $length;
 496  
 497          return bindec($data);
 498      }
 499  
 500      /**
 501       * @param int $fscod
 502       *
 503       * @return int|string|false
 504       */
 505  	public static function sampleRateCodeLookup($fscod) {
 506          static $sampleRateCodeLookup = array(
 507              0 => 48000,
 508              1 => 44100,
 509              2 => 32000,
 510              3 => 'reserved' // If the reserved code is indicated, the decoder should not attempt to decode audio and should mute.
 511          );
 512          return (isset($sampleRateCodeLookup[$fscod]) ? $sampleRateCodeLookup[$fscod] : false);
 513      }
 514  
 515      /**
 516       * @param int $fscod2
 517       *
 518       * @return int|string|false
 519       */
 520  	public static function sampleRateCodeLookup2($fscod2) {
 521          static $sampleRateCodeLookup2 = array(
 522              0 => 24000,
 523              1 => 22050,
 524              2 => 16000,
 525              3 => 'reserved' // If the reserved code is indicated, the decoder should not attempt to decode audio and should mute.
 526          );
 527          return (isset($sampleRateCodeLookup2[$fscod2]) ? $sampleRateCodeLookup2[$fscod2] : false);
 528      }
 529  
 530      /**
 531       * @param int $bsmod
 532       * @param int $acmod
 533       *
 534       * @return string|false
 535       */
 536  	public static function serviceTypeLookup($bsmod, $acmod) {
 537          static $serviceTypeLookup = array();
 538          if (empty($serviceTypeLookup)) {
 539              for ($i = 0; $i <= 7; $i++) {
 540                  $serviceTypeLookup[0][$i] = 'main audio service: complete main (CM)';
 541                  $serviceTypeLookup[1][$i] = 'main audio service: music and effects (ME)';
 542                  $serviceTypeLookup[2][$i] = 'associated service: visually impaired (VI)';
 543                  $serviceTypeLookup[3][$i] = 'associated service: hearing impaired (HI)';
 544                  $serviceTypeLookup[4][$i] = 'associated service: dialogue (D)';
 545                  $serviceTypeLookup[5][$i] = 'associated service: commentary (C)';
 546                  $serviceTypeLookup[6][$i] = 'associated service: emergency (E)';
 547              }
 548  
 549              $serviceTypeLookup[7][1]      = 'associated service: voice over (VO)';
 550              for ($i = 2; $i <= 7; $i++) {
 551                  $serviceTypeLookup[7][$i] = 'main audio service: karaoke';
 552              }
 553          }
 554          return (isset($serviceTypeLookup[$bsmod][$acmod]) ? $serviceTypeLookup[$bsmod][$acmod] : false);
 555      }
 556  
 557      /**
 558       * @param int $acmod
 559       *
 560       * @return array|false
 561       */
 562  	public static function audioCodingModeLookup($acmod) {
 563          // array(channel configuration, # channels (not incl LFE), channel order)
 564          static $audioCodingModeLookup = array (
 565              0 => array('channel_config'=>'1+1', 'num_channels'=>2, 'channel_order'=>'Ch1,Ch2'),
 566              1 => array('channel_config'=>'1/0', 'num_channels'=>1, 'channel_order'=>'C'),
 567              2 => array('channel_config'=>'2/0', 'num_channels'=>2, 'channel_order'=>'L,R'),
 568              3 => array('channel_config'=>'3/0', 'num_channels'=>3, 'channel_order'=>'L,C,R'),
 569              4 => array('channel_config'=>'2/1', 'num_channels'=>3, 'channel_order'=>'L,R,S'),
 570              5 => array('channel_config'=>'3/1', 'num_channels'=>4, 'channel_order'=>'L,C,R,S'),
 571              6 => array('channel_config'=>'2/2', 'num_channels'=>4, 'channel_order'=>'L,R,SL,SR'),
 572              7 => array('channel_config'=>'3/2', 'num_channels'=>5, 'channel_order'=>'L,C,R,SL,SR'),
 573          );
 574          return (isset($audioCodingModeLookup[$acmod]) ? $audioCodingModeLookup[$acmod] : false);
 575      }
 576  
 577      /**
 578       * @param int $cmixlev
 579       *
 580       * @return int|float|string|false
 581       */
 582  	public static function centerMixLevelLookup($cmixlev) {
 583          static $centerMixLevelLookup;
 584          if (empty($centerMixLevelLookup)) {
 585              $centerMixLevelLookup = array(
 586                  0 => pow(2, -3.0 / 6), // 0.707 (-3.0 dB)
 587                  1 => pow(2, -4.5 / 6), // 0.595 (-4.5 dB)
 588                  2 => pow(2, -6.0 / 6), // 0.500 (-6.0 dB)
 589                  3 => 'reserved'
 590              );
 591          }
 592          return (isset($centerMixLevelLookup[$cmixlev]) ? $centerMixLevelLookup[$cmixlev] : false);
 593      }
 594  
 595      /**
 596       * @param int $surmixlev
 597       *
 598       * @return int|float|string|false
 599       */
 600  	public static function surroundMixLevelLookup($surmixlev) {
 601          static $surroundMixLevelLookup;
 602          if (empty($surroundMixLevelLookup)) {
 603              $surroundMixLevelLookup = array(
 604                  0 => pow(2, -3.0 / 6),
 605                  1 => pow(2, -6.0 / 6),
 606                  2 => 0,
 607                  3 => 'reserved'
 608              );
 609          }
 610          return (isset($surroundMixLevelLookup[$surmixlev]) ? $surroundMixLevelLookup[$surmixlev] : false);
 611      }
 612  
 613      /**
 614       * @param int $dsurmod
 615       *
 616       * @return string|false
 617       */
 618  	public static function dolbySurroundModeLookup($dsurmod) {
 619          static $dolbySurroundModeLookup = array(
 620              0 => 'not indicated',
 621              1 => 'Not Dolby Surround encoded',
 622              2 => 'Dolby Surround encoded',
 623              3 => 'reserved'
 624          );
 625          return (isset($dolbySurroundModeLookup[$dsurmod]) ? $dolbySurroundModeLookup[$dsurmod] : false);
 626      }
 627  
 628      /**
 629       * @param int  $acmod
 630       * @param bool $lfeon
 631       *
 632       * @return array
 633       */
 634  	public static function channelsEnabledLookup($acmod, $lfeon) {
 635          $lookup = array(
 636              'ch1'=>($acmod == 0),
 637              'ch2'=>($acmod == 0),
 638              'left'=>($acmod > 1),
 639              'right'=>($acmod > 1),
 640              'center'=>(bool) ($acmod & 0x01),
 641              'surround_mono'=>false,
 642              'surround_left'=>false,
 643              'surround_right'=>false,
 644              'lfe'=>$lfeon);
 645          switch ($acmod) {
 646              case 4:
 647              case 5:
 648                  $lookup['surround_mono']  = true;
 649                  break;
 650              case 6:
 651              case 7:
 652                  $lookup['surround_left']  = true;
 653                  $lookup['surround_right'] = true;
 654                  break;
 655          }
 656          return $lookup;
 657      }
 658  
 659      /**
 660       * @param int $compre
 661       *
 662       * @return float|int
 663       */
 664  	public static function heavyCompression($compre) {
 665          // The first four bits indicate gain changes in 6.02dB increments which can be
 666          // implemented with an arithmetic shift operation. The following four bits
 667          // indicate linear gain changes, and require a 5-bit multiply.
 668          // We will represent the two 4-bit fields of compr as follows:
 669          //   X0 X1 X2 X3 . Y4 Y5 Y6 Y7
 670          // The meaning of the X values is most simply described by considering X to represent a 4-bit
 671          // signed integer with values from -8 to +7. The gain indicated by X is then (X + 1) * 6.02 dB. The
 672          // following table shows this in detail.
 673  
 674          // Meaning of 4 msb of compr
 675          //  7    +48.16 dB
 676          //  6    +42.14 dB
 677          //  5    +36.12 dB
 678          //  4    +30.10 dB
 679          //  3    +24.08 dB
 680          //  2    +18.06 dB
 681          //  1    +12.04 dB
 682          //  0     +6.02 dB
 683          // -1         0 dB
 684          // -2     -6.02 dB
 685          // -3    -12.04 dB
 686          // -4    -18.06 dB
 687          // -5    -24.08 dB
 688          // -6    -30.10 dB
 689          // -7    -36.12 dB
 690          // -8    -42.14 dB
 691  
 692          $fourbit = str_pad(decbin(($compre & 0xF0) >> 4), 4, '0', STR_PAD_LEFT);
 693          if ($fourbit[0] == '1') {
 694              $log_gain = -8 + bindec(substr($fourbit, 1));
 695          } else {
 696              $log_gain = bindec(substr($fourbit, 1));
 697          }
 698          $log_gain = ($log_gain + 1) * getid3_lib::RGADamplitude2dB(2);
 699  
 700          // The value of Y is a linear representation of a gain change of up to -6 dB. Y is considered to
 701          // be an unsigned fractional integer, with a leading value of 1, or: 0.1 Y4 Y5 Y6 Y7 (base 2). Y can
 702          // represent values between 0.111112 (or 31/32) and 0.100002 (or 1/2). Thus, Y can represent gain
 703          // changes from -0.28 dB to -6.02 dB.
 704  
 705          $lin_gain = (16 + ($compre & 0x0F)) / 32;
 706  
 707          // The combination of X and Y values allows compr to indicate gain changes from
 708          //  48.16 - 0.28 = +47.89 dB, to
 709          // -42.14 - 6.02 = -48.16 dB.
 710  
 711          return $log_gain - $lin_gain;
 712      }
 713  
 714      /**
 715       * @param int $roomtyp
 716       *
 717       * @return string|false
 718       */
 719  	public static function roomTypeLookup($roomtyp) {
 720          static $roomTypeLookup = array(
 721              0 => 'not indicated',
 722              1 => 'large room, X curve monitor',
 723              2 => 'small room, flat monitor',
 724              3 => 'reserved'
 725          );
 726          return (isset($roomTypeLookup[$roomtyp]) ? $roomTypeLookup[$roomtyp] : false);
 727      }
 728  
 729      /**
 730       * @param int $frmsizecod
 731       * @param int $fscod
 732       *
 733       * @return int|false
 734       */
 735  	public static function frameSizeLookup($frmsizecod, $fscod) {
 736          // LSB is whether padding is used or not
 737          $padding     = (bool) ($frmsizecod & 0x01);
 738          $framesizeid =        ($frmsizecod & 0x3E) >> 1;
 739  
 740          static $frameSizeLookup = array();
 741          if (empty($frameSizeLookup)) {
 742              $frameSizeLookup = array (
 743                  0  => array( 128,  138,  192),  //  32 kbps
 744                  1  => array( 160,  174,  240),  //  40 kbps
 745                  2  => array( 192,  208,  288),  //  48 kbps
 746                  3  => array( 224,  242,  336),  //  56 kbps
 747                  4  => array( 256,  278,  384),  //  64 kbps
 748                  5  => array( 320,  348,  480),  //  80 kbps
 749                  6  => array( 384,  416,  576),  //  96 kbps
 750                  7  => array( 448,  486,  672),  // 112 kbps
 751                  8  => array( 512,  556,  768),  // 128 kbps
 752                  9  => array( 640,  696,  960),  // 160 kbps
 753                  10 => array( 768,  834, 1152),  // 192 kbps
 754                  11 => array( 896,  974, 1344),  // 224 kbps
 755                  12 => array(1024, 1114, 1536),  // 256 kbps
 756                  13 => array(1280, 1392, 1920),  // 320 kbps
 757                  14 => array(1536, 1670, 2304),  // 384 kbps
 758                  15 => array(1792, 1950, 2688),  // 448 kbps
 759                  16 => array(2048, 2228, 3072),  // 512 kbps
 760                  17 => array(2304, 2506, 3456),  // 576 kbps
 761                  18 => array(2560, 2786, 3840)   // 640 kbps
 762              );
 763          }
 764          $paddingBytes = 0;
 765          if (($fscod == 1) && $padding) {
 766              // frame lengths are padded by 1 word (16 bits) at 44100
 767              // (fscode==1) means 44100Hz (see sampleRateCodeLookup)
 768              $paddingBytes = 2;
 769          }
 770          return (isset($frameSizeLookup[$framesizeid][$fscod]) ? $frameSizeLookup[$framesizeid][$fscod] + $paddingBytes : false);
 771      }
 772  
 773      /**
 774       * @param int $frmsizecod
 775       *
 776       * @return int|false
 777       */
 778  	public static function bitrateLookup($frmsizecod) {
 779          // LSB is whether padding is used or not
 780          $padding     = (bool) ($frmsizecod & 0x01);
 781          $framesizeid =        ($frmsizecod & 0x3E) >> 1;
 782  
 783          static $bitrateLookup = array(
 784               0 =>  32000,
 785               1 =>  40000,
 786               2 =>  48000,
 787               3 =>  56000,
 788               4 =>  64000,
 789               5 =>  80000,
 790               6 =>  96000,
 791               7 => 112000,
 792               8 => 128000,
 793               9 => 160000,
 794              10 => 192000,
 795              11 => 224000,
 796              12 => 256000,
 797              13 => 320000,
 798              14 => 384000,
 799              15 => 448000,
 800              16 => 512000,
 801              17 => 576000,
 802              18 => 640000,
 803          );
 804          return (isset($bitrateLookup[$framesizeid]) ? $bitrateLookup[$framesizeid] : false);
 805      }
 806  
 807      /**
 808       * @param int $numblkscod
 809       *
 810       * @return int|false
 811       */
 812  	public static function blocksPerSyncFrame($numblkscod) {
 813          static $blocksPerSyncFrameLookup = array(
 814              0 => 1,
 815              1 => 2,
 816              2 => 3,
 817              3 => 6,
 818          );
 819          return (isset($blocksPerSyncFrameLookup[$numblkscod]) ? $blocksPerSyncFrameLookup[$numblkscod] : false);
 820      }
 821  
 822  
 823  }


Generated: Mon Aug 3 01:00:04 2020 Cross-referenced by PHPXref 0.7.1