home *** CD-ROM | disk | FTP | other *** search
/ HTML Examples / WP.iso / wordpress2 / wp-includes / ID3 / module.audio.ac3.php < prev    next >
Encoding:
PHP Script  |  2017-07-31  |  37.3 KB  |  734 lines
  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 = 0x0B77;
  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.         $tempAC3header = $this->fread(100); // should be enough to cover all data, there are some variable-length fields...?
  59.         $this->AC3header['syncinfo']  =     getid3_lib::BigEndian2Int(substr($tempAC3header, 0, 2));
  60.         $this->AC3header['bsi']       =     getid3_lib::BigEndian2Bin(substr($tempAC3header, 2));
  61.         $thisfile_ac3_raw_bsi['bsid'] = (getid3_lib::LittleEndian2Int(substr($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
  62.         unset($tempAC3header);
  63.  
  64.         if ($this->AC3header['syncinfo'] !== self::syncword) {
  65.             if (!$this->isDependencyFor('matroska')) {
  66.                 unset($info['fileformat'], $info['ac3']);
  67.                 return $this->error('Expecting "'.dechex(self::syncword).'" at offset '.$info['avdataoffset'].', found "'.dechex($this->AC3header['syncinfo']).'"');
  68.             }
  69.         }
  70.  
  71.         $info['audio']['dataformat']   = 'ac3';
  72.         $info['audio']['bitrate_mode'] = 'cbr';
  73.         $info['audio']['lossless']     = false;
  74.  
  75.         if ($thisfile_ac3_raw_bsi['bsid'] <= 8) {
  76.  
  77.             $thisfile_ac3_raw_bsi['crc1']       = getid3_lib::Bin2Dec($this->readHeaderBSI(16));
  78.             $thisfile_ac3_raw_bsi['fscod']      =                     $this->readHeaderBSI(2);   // 5.4.1.3
  79.             $thisfile_ac3_raw_bsi['frmsizecod'] =                     $this->readHeaderBSI(6);   // 5.4.1.4
  80.             if ($thisfile_ac3_raw_bsi['frmsizecod'] > 37) { // binary: 100101 - see Table 5.18 Frame Size Code Table (1 word = 16 bits)
  81.                 $this->warning('Unexpected ac3.bsi.frmsizecod value: '.$thisfile_ac3_raw_bsi['frmsizecod'].', bitrate not set correctly');
  82.             }
  83.  
  84.             $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
  85.             $thisfile_ac3_raw_bsi['bsmod'] = $this->readHeaderBSI(3);
  86.             $thisfile_ac3_raw_bsi['acmod'] = $this->readHeaderBSI(3);
  87.  
  88.             if ($thisfile_ac3_raw_bsi['acmod'] & 0x01) {
  89.                 // If the lsb of acmod is a 1, center channel is in use and cmixlev follows in the bit stream.
  90.                 $thisfile_ac3_raw_bsi['cmixlev'] = $this->readHeaderBSI(2);
  91.                 $thisfile_ac3['center_mix_level'] = self::centerMixLevelLookup($thisfile_ac3_raw_bsi['cmixlev']);
  92.             }
  93.  
  94.             if ($thisfile_ac3_raw_bsi['acmod'] & 0x04) {
  95.                 // If the msb of acmod is a 1, surround channels are in use and surmixlev follows in the bit stream.
  96.                 $thisfile_ac3_raw_bsi['surmixlev'] = $this->readHeaderBSI(2);
  97.                 $thisfile_ac3['surround_mix_level'] = self::surroundMixLevelLookup($thisfile_ac3_raw_bsi['surmixlev']);
  98.             }
  99.  
  100.             if ($thisfile_ac3_raw_bsi['acmod'] == 0x02) {
  101.                 // When operating in the two channel mode, this 2-bit code indicates whether or not the program has been encoded in Dolby Surround.
  102.                 $thisfile_ac3_raw_bsi['dsurmod'] = $this->readHeaderBSI(2);
  103.                 $thisfile_ac3['dolby_surround_mode'] = self::dolbySurroundModeLookup($thisfile_ac3_raw_bsi['dsurmod']);
  104.             }
  105.  
  106.             $thisfile_ac3_raw_bsi['flags']['lfeon'] = (bool) $this->readHeaderBSI(1);
  107.  
  108.             // This indicates how far the average dialogue level is below digital 100 percent. Valid values are 1-31.
  109.             // 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.
  110.             $thisfile_ac3_raw_bsi['dialnorm'] = $this->readHeaderBSI(5);                 // 5.4.2.8 dialnorm: Dialogue Normalization, 5 Bits
  111.  
  112.             $thisfile_ac3_raw_bsi['flags']['compr'] = (bool) $this->readHeaderBSI(1);       // 5.4.2.9 compre: Compression Gain Word Exists, 1 Bit
  113.             if ($thisfile_ac3_raw_bsi['flags']['compr']) {
  114.                 $thisfile_ac3_raw_bsi['compr'] = $this->readHeaderBSI(8);                // 5.4.2.10 compr: Compression Gain Word, 8 Bits
  115.                 $thisfile_ac3['heavy_compression'] = self::heavyCompression($thisfile_ac3_raw_bsi['compr']);
  116.             }
  117.  
  118.             $thisfile_ac3_raw_bsi['flags']['langcod'] = (bool) $this->readHeaderBSI(1);     // 5.4.2.11 langcode: Language Code Exists, 1 Bit
  119.             if ($thisfile_ac3_raw_bsi['flags']['langcod']) {
  120.                 $thisfile_ac3_raw_bsi['langcod'] = $this->readHeaderBSI(8);              // 5.4.2.12 langcod: Language Code, 8 Bits
  121.             }
  122.  
  123.             $thisfile_ac3_raw_bsi['flags']['audprodinfo'] = (bool) $this->readHeaderBSI(1);  // 5.4.2.13 audprodie: Audio Production Information Exists, 1 Bit
  124.             if ($thisfile_ac3_raw_bsi['flags']['audprodinfo']) {
  125.                 $thisfile_ac3_raw_bsi['mixlevel'] = $this->readHeaderBSI(5);             // 5.4.2.14 mixlevel: Mixing Level, 5 Bits
  126.                 $thisfile_ac3_raw_bsi['roomtyp']  = $this->readHeaderBSI(2);             // 5.4.2.15 roomtyp: Room Type, 2 Bits
  127.  
  128.                 $thisfile_ac3['mixing_level'] = (80 + $thisfile_ac3_raw_bsi['mixlevel']).'dB';
  129.                 $thisfile_ac3['room_type']    = self::roomTypeLookup($thisfile_ac3_raw_bsi['roomtyp']);
  130.             }
  131.  
  132.  
  133.             $thisfile_ac3_raw_bsi['dialnorm2'] = $this->readHeaderBSI(5);                // 5.4.2.16 dialnorm2: Dialogue Normalization, ch2, 5 Bits
  134.             $thisfile_ac3['dialogue_normalization2'] = '-'.$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.
  135.  
  136.             $thisfile_ac3_raw_bsi['flags']['compr2'] = (bool) $this->readHeaderBSI(1);       // 5.4.2.17 compr2e: Compression Gain Word Exists, ch2, 1 Bit
  137.             if ($thisfile_ac3_raw_bsi['flags']['compr2']) {
  138.                 $thisfile_ac3_raw_bsi['compr2'] = $this->readHeaderBSI(8);               // 5.4.2.18 compr2: Compression Gain Word, ch2, 8 Bits
  139.                 $thisfile_ac3['heavy_compression2'] = self::heavyCompression($thisfile_ac3_raw_bsi['compr2']);
  140.             }
  141.  
  142.             $thisfile_ac3_raw_bsi['flags']['langcod2'] = (bool) $this->readHeaderBSI(1);    // 5.4.2.19 langcod2e: Language Code Exists, ch2, 1 Bit
  143.             if ($thisfile_ac3_raw_bsi['flags']['langcod2']) {
  144.                 $thisfile_ac3_raw_bsi['langcod2'] = $this->readHeaderBSI(8);             // 5.4.2.20 langcod2: Language Code, ch2, 8 Bits
  145.             }
  146.  
  147.             $thisfile_ac3_raw_bsi['flags']['audprodinfo2'] = (bool) $this->readHeaderBSI(1); // 5.4.2.21 audprodi2e: Audio Production Information Exists, ch2, 1 Bit
  148.             if ($thisfile_ac3_raw_bsi['flags']['audprodinfo2']) {
  149.                 $thisfile_ac3_raw_bsi['mixlevel2'] = $this->readHeaderBSI(5);            // 5.4.2.22 mixlevel2: Mixing Level, ch2, 5 Bits
  150.                 $thisfile_ac3_raw_bsi['roomtyp2']  = $this->readHeaderBSI(2);            // 5.4.2.23 roomtyp2: Room Type, ch2, 2 Bits
  151.  
  152.                 $thisfile_ac3['mixing_level2'] = (80 + $thisfile_ac3_raw_bsi['mixlevel2']).'dB';
  153.                 $thisfile_ac3['room_type2']    = self::roomTypeLookup($thisfile_ac3_raw_bsi['roomtyp2']);
  154.             }
  155.  
  156.             $thisfile_ac3_raw_bsi['copyright'] = (bool) $this->readHeaderBSI(1);         // 5.4.2.24 copyrightb: Copyright Bit, 1 Bit
  157.  
  158.             $thisfile_ac3_raw_bsi['original']  = (bool) $this->readHeaderBSI(1);         // 5.4.2.25 origbs: Original Bit Stream, 1 Bit
  159.  
  160.             $thisfile_ac3_raw_bsi['flags']['timecod1'] = $this->readHeaderBSI(2);            // 5.4.2.26 timecod1e, timcode2e: Time Code (first and second) Halves Exist, 2 Bits
  161.             if ($thisfile_ac3_raw_bsi['flags']['timecod1'] & 0x01) {
  162.                 $thisfile_ac3_raw_bsi['timecod1'] = $this->readHeaderBSI(14);            // 5.4.2.27 timecod1: Time code first half, 14 bits
  163.                 $thisfile_ac3['timecode1'] = 0;
  164.                 $thisfile_ac3['timecode1'] += (($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
  165.                 $thisfile_ac3['timecode1'] += (($thisfile_ac3_raw_bsi['timecod1'] & 0x01F8) >>  3) *   60;  // The next 6 bits represent the time in minutes, with valid values of 0∩┐╜59
  166.                 $thisfile_ac3['timecode1'] += (($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)
  167.             }
  168.             if ($thisfile_ac3_raw_bsi['flags']['timecod1'] & 0x02) {
  169.                 $thisfile_ac3_raw_bsi['timecod2'] = $this->readHeaderBSI(14);            // 5.4.2.28 timecod2: Time code second half, 14 bits
  170.                 $thisfile_ac3['timecode2'] = 0;
  171.                 $thisfile_ac3['timecode2'] += (($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)
  172.                 $thisfile_ac3['timecode2'] += (($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)
  173.                 $thisfile_ac3['timecode2'] += (($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
  174.             }
  175.  
  176.             $thisfile_ac3_raw_bsi['flags']['addbsi'] = (bool) $this->readHeaderBSI(1);
  177.             if ($thisfile_ac3_raw_bsi['flags']['addbsi']) {
  178.                 $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.
  179.  
  180.                 $this->AC3header['bsi'] .= getid3_lib::BigEndian2Bin($this->fread($thisfile_ac3_raw_bsi['addbsi_length']));
  181.  
  182.                 $thisfile_ac3_raw_bsi['addbsi_data'] = substr($this->AC3header['bsi'], $this->BSIoffset, $thisfile_ac3_raw_bsi['addbsi_length'] * 8);
  183.                 $this->BSIoffset += $thisfile_ac3_raw_bsi['addbsi_length'] * 8;
  184.             }
  185.  
  186.  
  187.         } elseif ($thisfile_ac3_raw_bsi['bsid'] <= 16) { // E-AC3
  188.  
  189.  
  190. $this->error('E-AC3 parsing is incomplete and experimental in this version of getID3 ('.$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.');
  191.             $info['audio']['dataformat'] = 'eac3';
  192.  
  193.             $thisfile_ac3_raw_bsi['strmtyp']          =        $this->readHeaderBSI(2);
  194.             $thisfile_ac3_raw_bsi['substreamid']      =        $this->readHeaderBSI(3);
  195.             $thisfile_ac3_raw_bsi['frmsiz']           =        $this->readHeaderBSI(11);
  196.             $thisfile_ac3_raw_bsi['fscod']            =        $this->readHeaderBSI(2);
  197.             if ($thisfile_ac3_raw_bsi['fscod'] == 3) {
  198.                 $thisfile_ac3_raw_bsi['fscod2']       =        $this->readHeaderBSI(2);
  199.                 $thisfile_ac3_raw_bsi['numblkscod'] = 3; // six blocks per syncframe
  200.             } else {
  201.                 $thisfile_ac3_raw_bsi['numblkscod']   =        $this->readHeaderBSI(2);
  202.             }
  203.             $thisfile_ac3['bsi']['blocks_per_sync_frame'] = self::blocksPerSyncFrame($thisfile_ac3_raw_bsi['numblkscod']);
  204.             $thisfile_ac3_raw_bsi['acmod']            =        $this->readHeaderBSI(3);
  205.             $thisfile_ac3_raw_bsi['flags']['lfeon']   = (bool) $this->readHeaderBSI(1);
  206.             $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
  207.             $thisfile_ac3_raw_bsi['dialnorm']         =        $this->readHeaderBSI(5);
  208.             $thisfile_ac3_raw_bsi['flags']['compr']       = (bool) $this->readHeaderBSI(1);
  209.             if ($thisfile_ac3_raw_bsi['flags']['compr']) {
  210.                 $thisfile_ac3_raw_bsi['compr']        =        $this->readHeaderBSI(8);
  211.             }
  212.             if ($thisfile_ac3_raw_bsi['acmod'] == 0) { // if 1+1 mode (dual mono, so some items need a second value)
  213.                 $thisfile_ac3_raw_bsi['dialnorm2']    =        $this->readHeaderBSI(5);
  214.                 $thisfile_ac3_raw_bsi['flags']['compr2']  = (bool) $this->readHeaderBSI(1);
  215.                 if ($thisfile_ac3_raw_bsi['flags']['compr2']) {
  216.                     $thisfile_ac3_raw_bsi['compr2']   =        $this->readHeaderBSI(8);
  217.                 }
  218.             }
  219.             if ($thisfile_ac3_raw_bsi['strmtyp'] == 1) { // if dependent stream
  220.                 $thisfile_ac3_raw_bsi['flags']['chanmap'] = (bool) $this->readHeaderBSI(1);
  221.                 if ($thisfile_ac3_raw_bsi['flags']['chanmap']) {
  222.                     $thisfile_ac3_raw_bsi['chanmap']  =        $this->readHeaderBSI(8);
  223.                 }
  224.             }
  225.             $thisfile_ac3_raw_bsi['flags']['mixmdat']     = (bool) $this->readHeaderBSI(1);
  226.             if ($thisfile_ac3_raw_bsi['flags']['mixmdat']) { // Mixing metadata
  227.                 if ($thisfile_ac3_raw_bsi['acmod'] > 2) { // if more than 2 channels
  228.                     $thisfile_ac3_raw_bsi['dmixmod']  =        $this->readHeaderBSI(2);
  229.                 }
  230.                 if (($thisfile_ac3_raw_bsi['acmod'] & 0x01) && ($thisfile_ac3_raw_bsi['acmod'] > 2)) { // if three front channels exist
  231.                     $thisfile_ac3_raw_bsi['ltrtcmixlev'] =        $this->readHeaderBSI(3);
  232.                     $thisfile_ac3_raw_bsi['lorocmixlev'] =        $this->readHeaderBSI(3);
  233.                 }
  234.                 if ($thisfile_ac3_raw_bsi['acmod'] & 0x04) { // if a surround channel exists
  235.                     $thisfile_ac3_raw_bsi['ltrtsurmixlev'] =        $this->readHeaderBSI(3);
  236.                     $thisfile_ac3_raw_bsi['lorosurmixlev'] =        $this->readHeaderBSI(3);
  237.                 }
  238.                 if ($thisfile_ac3_raw_bsi['flags']['lfeon']) { // if the LFE channel exists
  239.                     $thisfile_ac3_raw_bsi['flags']['lfemixlevcod'] = (bool) $this->readHeaderBSI(1);
  240.                     if ($thisfile_ac3_raw_bsi['flags']['lfemixlevcod']) {
  241.                         $thisfile_ac3_raw_bsi['lfemixlevcod']  =        $this->readHeaderBSI(5);
  242.                     }
  243.                 }
  244.                 if ($thisfile_ac3_raw_bsi['strmtyp'] == 0) { // if independent stream
  245.                     $thisfile_ac3_raw_bsi['flags']['pgmscl'] = (bool) $this->readHeaderBSI(1);
  246.                     if ($thisfile_ac3_raw_bsi['flags']['pgmscl']) {
  247.                         $thisfile_ac3_raw_bsi['pgmscl']  =        $this->readHeaderBSI(6);
  248.                     }
  249.                     if ($thisfile_ac3_raw_bsi['acmod'] == 0) { // if 1+1 mode (dual mono, so some items need a second value)
  250.                         $thisfile_ac3_raw_bsi['flags']['pgmscl2'] = (bool) $this->readHeaderBSI(1);
  251.                         if ($thisfile_ac3_raw_bsi['flags']['pgmscl2']) {
  252.                             $thisfile_ac3_raw_bsi['pgmscl2']  =        $this->readHeaderBSI(6);
  253.                         }
  254.                     }
  255.                     $thisfile_ac3_raw_bsi['flags']['extpgmscl'] = (bool) $this->readHeaderBSI(1);
  256.                     if ($thisfile_ac3_raw_bsi['flags']['extpgmscl']) {
  257.                         $thisfile_ac3_raw_bsi['extpgmscl']  =        $this->readHeaderBSI(6);
  258.                     }
  259.                     $thisfile_ac3_raw_bsi['mixdef']  =        $this->readHeaderBSI(2);
  260.                     if ($thisfile_ac3_raw_bsi['mixdef'] == 1) { // mixing option 2
  261.                         $thisfile_ac3_raw_bsi['premixcmpsel']  = (bool) $this->readHeaderBSI(1);
  262.                         $thisfile_ac3_raw_bsi['drcsrc']        = (bool) $this->readHeaderBSI(1);
  263.                         $thisfile_ac3_raw_bsi['premixcmpscl']  =        $this->readHeaderBSI(3);
  264.                     } elseif ($thisfile_ac3_raw_bsi['mixdef'] == 2) { // mixing option 3
  265.                         $thisfile_ac3_raw_bsi['mixdata']       =        $this->readHeaderBSI(12);
  266.                     } elseif ($thisfile_ac3_raw_bsi['mixdef'] == 3) { // mixing option 4
  267.                         $mixdefbitsread = 0;
  268.                         $thisfile_ac3_raw_bsi['mixdeflen']     =        $this->readHeaderBSI(5); $mixdefbitsread += 5;
  269.                         $thisfile_ac3_raw_bsi['flags']['mixdata2'] = (bool) $this->readHeaderBSI(1); $mixdefbitsread += 1;
  270.                         if ($thisfile_ac3_raw_bsi['flags']['mixdata2']) {
  271.                             $thisfile_ac3_raw_bsi['premixcmpsel']  = (bool) $this->readHeaderBSI(1); $mixdefbitsread += 1;
  272.                             $thisfile_ac3_raw_bsi['drcsrc']        = (bool) $this->readHeaderBSI(1); $mixdefbitsread += 1;
  273.                             $thisfile_ac3_raw_bsi['premixcmpscl']  =        $this->readHeaderBSI(3); $mixdefbitsread += 3;
  274.                             $thisfile_ac3_raw_bsi['flags']['extpgmlscl']   = (bool) $this->readHeaderBSI(1); $mixdefbitsread += 1;
  275.                             if ($thisfile_ac3_raw_bsi['flags']['extpgmlscl']) {
  276.                                 $thisfile_ac3_raw_bsi['extpgmlscl']    =        $this->readHeaderBSI(4); $mixdefbitsread += 4;
  277.                             }
  278.                             $thisfile_ac3_raw_bsi['flags']['extpgmcscl']   = (bool) $this->readHeaderBSI(1); $mixdefbitsread += 1;
  279.                             if ($thisfile_ac3_raw_bsi['flags']['extpgmcscl']) {
  280.                                 $thisfile_ac3_raw_bsi['extpgmcscl']    =        $this->readHeaderBSI(4); $mixdefbitsread += 4;
  281.                             }
  282.                             $thisfile_ac3_raw_bsi['flags']['extpgmrscl']   = (bool) $this->readHeaderBSI(1); $mixdefbitsread += 1;
  283.                             if ($thisfile_ac3_raw_bsi['flags']['extpgmrscl']) {
  284.                                 $thisfile_ac3_raw_bsi['extpgmrscl']    =        $this->readHeaderBSI(4);
  285.                             }
  286.                             $thisfile_ac3_raw_bsi['flags']['extpgmlsscl']  = (bool) $this->readHeaderBSI(1); $mixdefbitsread += 1;
  287.                             if ($thisfile_ac3_raw_bsi['flags']['extpgmlsscl']) {
  288.                                 $thisfile_ac3_raw_bsi['extpgmlsscl']   =        $this->readHeaderBSI(4); $mixdefbitsread += 4;
  289.                             }
  290.                             $thisfile_ac3_raw_bsi['flags']['extpgmrsscl']  = (bool) $this->readHeaderBSI(1); $mixdefbitsread += 1;
  291.                             if ($thisfile_ac3_raw_bsi['flags']['extpgmrsscl']) {
  292.                                 $thisfile_ac3_raw_bsi['extpgmrsscl']   =        $this->readHeaderBSI(4); $mixdefbitsread += 4;
  293.                             }
  294.                             $thisfile_ac3_raw_bsi['flags']['extpgmlfescl'] = (bool) $this->readHeaderBSI(1); $mixdefbitsread += 1;
  295.                             if ($thisfile_ac3_raw_bsi['flags']['extpgmlfescl']) {
  296.                                 $thisfile_ac3_raw_bsi['extpgmlfescl']  =        $this->readHeaderBSI(4); $mixdefbitsread += 4;
  297.                             }
  298.                             $thisfile_ac3_raw_bsi['flags']['dmixscl']      = (bool) $this->readHeaderBSI(1); $mixdefbitsread += 1;
  299.                             if ($thisfile_ac3_raw_bsi['flags']['dmixscl']) {
  300.                                 $thisfile_ac3_raw_bsi['dmixscl']       =        $this->readHeaderBSI(4); $mixdefbitsread += 4;
  301.                             }
  302.                             $thisfile_ac3_raw_bsi['flags']['addch']        = (bool) $this->readHeaderBSI(1); $mixdefbitsread += 1;
  303.                             if ($thisfile_ac3_raw_bsi['flags']['addch']) {
  304.                                 $thisfile_ac3_raw_bsi['flags']['extpgmaux1scl']   = (bool) $this->readHeaderBSI(1); $mixdefbitsread += 1;
  305.                                 if ($thisfile_ac3_raw_bsi['flags']['extpgmaux1scl']) {
  306.                                     $thisfile_ac3_raw_bsi['extpgmaux1scl']    =        $this->readHeaderBSI(4); $mixdefbitsread += 4;
  307.                                 }
  308.                                 $thisfile_ac3_raw_bsi['flags']['extpgmaux2scl']   = (bool) $this->readHeaderBSI(1); $mixdefbitsread += 1;
  309.                                 if ($thisfile_ac3_raw_bsi['flags']['extpgmaux2scl']) {
  310.                                     $thisfile_ac3_raw_bsi['extpgmaux2scl']    =        $this->readHeaderBSI(4); $mixdefbitsread += 4;
  311.                                 }
  312.                             }
  313.                         }
  314.                         $thisfile_ac3_raw_bsi['flags']['mixdata3'] = (bool) $this->readHeaderBSI(1); $mixdefbitsread += 1;
  315.                         if ($thisfile_ac3_raw_bsi['flags']['mixdata3']) {
  316.                             $thisfile_ac3_raw_bsi['spchdat']   =        $this->readHeaderBSI(5); $mixdefbitsread += 5;
  317.                             $thisfile_ac3_raw_bsi['flags']['addspchdat'] = (bool) $this->readHeaderBSI(1); $mixdefbitsread += 1;
  318.                             if ($thisfile_ac3_raw_bsi['flags']['addspchdat']) {
  319.                                 $thisfile_ac3_raw_bsi['spchdat1']   =         $this->readHeaderBSI(5); $mixdefbitsread += 5;
  320.                                 $thisfile_ac3_raw_bsi['spchan1att'] =         $this->readHeaderBSI(2); $mixdefbitsread += 2;
  321.                                 $thisfile_ac3_raw_bsi['flags']['addspchdat1'] = (bool) $this->readHeaderBSI(1); $mixdefbitsread += 1;
  322.                                 if ($thisfile_ac3_raw_bsi['flags']['addspchdat1']) {
  323.                                     $thisfile_ac3_raw_bsi['spchdat2']   =         $this->readHeaderBSI(5); $mixdefbitsread += 5;
  324.                                     $thisfile_ac3_raw_bsi['spchan2att'] =         $this->readHeaderBSI(3); $mixdefbitsread += 3;
  325.                                 }
  326.                             }
  327.                         }
  328.                         $mixdata_bits = (8 * ($thisfile_ac3_raw_bsi['mixdeflen'] + 2)) - $mixdefbitsread;
  329.                         $mixdata_fill = (($mixdata_bits % 8) ? 8 - ($mixdata_bits % 8) : 0);
  330.                         $thisfile_ac3_raw_bsi['mixdata']     =        $this->readHeaderBSI($mixdata_bits);
  331.                         $thisfile_ac3_raw_bsi['mixdatafill'] =        $this->readHeaderBSI($mixdata_fill);
  332.                         unset($mixdefbitsread, $mixdata_bits, $mixdata_fill);
  333.                     }
  334.                     if ($thisfile_ac3_raw_bsi['acmod'] < 2) { // if mono or dual mono source
  335.                         $thisfile_ac3_raw_bsi['flags']['paninfo'] = (bool) $this->readHeaderBSI(1);
  336.                         if ($thisfile_ac3_raw_bsi['flags']['paninfo']) {
  337.                             $thisfile_ac3_raw_bsi['panmean']   =        $this->readHeaderBSI(8);
  338.                             $thisfile_ac3_raw_bsi['paninfo']   =        $this->readHeaderBSI(6);
  339.                         }
  340.                         if ($thisfile_ac3_raw_bsi['acmod'] == 0) { // if 1+1 mode (dual mono, so some items need a second value)
  341.                             $thisfile_ac3_raw_bsi['flags']['paninfo2'] = (bool) $this->readHeaderBSI(1);
  342.                             if ($thisfile_ac3_raw_bsi['flags']['paninfo2']) {
  343.                                 $thisfile_ac3_raw_bsi['panmean2']   =        $this->readHeaderBSI(8);
  344.                                 $thisfile_ac3_raw_bsi['paninfo2']   =        $this->readHeaderBSI(6);
  345.                             }
  346.                         }
  347.                     }
  348.                     $thisfile_ac3_raw_bsi['flags']['frmmixcfginfo'] = (bool) $this->readHeaderBSI(1);
  349.                     if ($thisfile_ac3_raw_bsi['flags']['frmmixcfginfo']) { // mixing configuration information
  350.                         if ($thisfile_ac3_raw_bsi['numblkscod'] == 0) {
  351.                             $thisfile_ac3_raw_bsi['blkmixcfginfo'][0]  =        $this->readHeaderBSI(5);
  352.                         } else {
  353.                             for ($blk = 0; $blk < $thisfile_ac3_raw_bsi['numblkscod']; $blk++) {
  354.                                 $thisfile_ac3_raw_bsi['flags']['blkmixcfginfo'.$blk] = (bool) $this->readHeaderBSI(1);
  355.                                 if ($thisfile_ac3_raw_bsi['flags']['blkmixcfginfo'.$blk]) { // mixing configuration information
  356.                                     $thisfile_ac3_raw_bsi['blkmixcfginfo'][$blk]  =        $this->readHeaderBSI(5);
  357.                                 }
  358.                             }
  359.                         }
  360.                     }
  361.                 }
  362.             }
  363.             $thisfile_ac3_raw_bsi['flags']['infomdat']          = (bool) $this->readHeaderBSI(1);
  364.             if ($thisfile_ac3_raw_bsi['flags']['infomdat']) { // Informational metadata
  365.                 $thisfile_ac3_raw_bsi['bsmod']                  =        $this->readHeaderBSI(3);
  366.                 $thisfile_ac3_raw_bsi['flags']['copyrightb']    = (bool) $this->readHeaderBSI(1);
  367.                 $thisfile_ac3_raw_bsi['flags']['origbs']        = (bool) $this->readHeaderBSI(1);
  368.                 if ($thisfile_ac3_raw_bsi['acmod'] == 2) { //  if in 2/0 mode
  369.                     $thisfile_ac3_raw_bsi['dsurmod']            =        $this->readHeaderBSI(2);
  370.                     $thisfile_ac3_raw_bsi['dheadphonmod']       =        $this->readHeaderBSI(2);
  371.                 }
  372.                 if ($thisfile_ac3_raw_bsi['acmod'] >= 6) { //  if both surround channels exist
  373.                     $thisfile_ac3_raw_bsi['dsurexmod']          =        $this->readHeaderBSI(2);
  374.                 }
  375.                 $thisfile_ac3_raw_bsi['flags']['audprodi']      = (bool) $this->readHeaderBSI(1);
  376.                 if ($thisfile_ac3_raw_bsi['flags']['audprodi']) {
  377.                     $thisfile_ac3_raw_bsi['mixlevel']           =        $this->readHeaderBSI(5);
  378.                     $thisfile_ac3_raw_bsi['roomtyp']            =        $this->readHeaderBSI(2);
  379.                     $thisfile_ac3_raw_bsi['flags']['adconvtyp'] = (bool) $this->readHeaderBSI(1);
  380.                 }
  381.                 if ($thisfile_ac3_raw_bsi['acmod'] == 0) { //  if 1+1 mode (dual mono, so some items need a second value)
  382.                     $thisfile_ac3_raw_bsi['flags']['audprodi2']      = (bool) $this->readHeaderBSI(1);
  383.                     if ($thisfile_ac3_raw_bsi['flags']['audprodi2']) {
  384.                         $thisfile_ac3_raw_bsi['mixlevel2']           =        $this->readHeaderBSI(5);
  385.                         $thisfile_ac3_raw_bsi['roomtyp2']            =        $this->readHeaderBSI(2);
  386.                         $thisfile_ac3_raw_bsi['flags']['adconvtyp2'] = (bool) $this->readHeaderBSI(1);
  387.                     }
  388.                 }
  389.                 if ($thisfile_ac3_raw_bsi['fscod'] < 3) { // if not half sample rate
  390.                     $thisfile_ac3_raw_bsi['flags']['sourcefscod'] = (bool) $this->readHeaderBSI(1);
  391.                 }
  392.             }
  393.             if (($thisfile_ac3_raw_bsi['strmtyp'] == 0) && ($thisfile_ac3_raw_bsi['numblkscod'] != 3)) { //  if both surround channels exist
  394.                 $thisfile_ac3_raw_bsi['flags']['convsync'] = (bool) $this->readHeaderBSI(1);
  395.             }
  396.             if ($thisfile_ac3_raw_bsi['strmtyp'] == 2) { //  if bit stream converted from AC-3
  397.                 if ($thisfile_ac3_raw_bsi['numblkscod'] != 3) { // 6 blocks per syncframe
  398.                     $thisfile_ac3_raw_bsi['flags']['blkid']  = 1;
  399.                 } else {
  400.                     $thisfile_ac3_raw_bsi['flags']['blkid']  = (bool) $this->readHeaderBSI(1);
  401.                 }
  402.                 if ($thisfile_ac3_raw_bsi['flags']['blkid']) {
  403.                     $thisfile_ac3_raw_bsi['frmsizecod']  =        $this->readHeaderBSI(6);
  404.                 }
  405.             }
  406.             $thisfile_ac3_raw_bsi['flags']['addbsi']  = (bool) $this->readHeaderBSI(1);
  407.             if ($thisfile_ac3_raw_bsi['flags']['addbsi']) {
  408.                 $thisfile_ac3_raw_bsi['addbsil']  =        $this->readHeaderBSI(6);
  409.                 $thisfile_ac3_raw_bsi['addbsi']   =        $this->readHeaderBSI(($thisfile_ac3_raw_bsi['addbsil'] + 1) * 8);
  410.             }
  411.  
  412.         } else {
  413.  
  414.             $this->error('Bit stream identification is version '.$thisfile_ac3_raw_bsi['bsid'].', but getID3() only understands up to version 16. Please submit a support ticket with a sample file.');
  415.             unset($info['ac3']);
  416.             return false;
  417.  
  418.         }
  419.  
  420.         if (isset($thisfile_ac3_raw_bsi['fscod2'])) {
  421.             $thisfile_ac3['sample_rate'] = self::sampleRateCodeLookup2($thisfile_ac3_raw_bsi['fscod2']);
  422.         } else {
  423.             $thisfile_ac3['sample_rate'] = self::sampleRateCodeLookup($thisfile_ac3_raw_bsi['fscod']);
  424.         }
  425.         if ($thisfile_ac3_raw_bsi['fscod'] <= 3) {
  426.             $info['audio']['sample_rate'] = $thisfile_ac3['sample_rate'];
  427.         } else {
  428.             $this->warning('Unexpected ac3.bsi.fscod value: '.$thisfile_ac3_raw_bsi['fscod']);
  429.         }
  430.         if (isset($thisfile_ac3_raw_bsi['frmsizecod'])) {
  431.             $thisfile_ac3['frame_length'] = self::frameSizeLookup($thisfile_ac3_raw_bsi['frmsizecod'], $thisfile_ac3_raw_bsi['fscod']);
  432.             $thisfile_ac3['bitrate']      = self::bitrateLookup($thisfile_ac3_raw_bsi['frmsizecod']);
  433.         } elseif (!empty($thisfile_ac3_raw_bsi['frmsiz'])) {
  434. // this isn't right, but it's (usually) close, roughly 5% less than it should be.
  435. // but WHERE is the actual bitrate value stored in EAC3?? email info@getid3.org if you know!
  436.             $thisfile_ac3['bitrate']      = ($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.
  437. // kludge-fix to make it approximately the expected value, still not "right":
  438. $thisfile_ac3['bitrate'] = round(($thisfile_ac3['bitrate'] * 1.05) / 16000) * 16000;
  439.         }
  440.         $info['audio']['bitrate'] = $thisfile_ac3['bitrate'];
  441.  
  442.         $thisfile_ac3['service_type'] = self::serviceTypeLookup($thisfile_ac3_raw_bsi['bsmod'], $thisfile_ac3_raw_bsi['acmod']);
  443.         $ac3_coding_mode = self::audioCodingModeLookup($thisfile_ac3_raw_bsi['acmod']);
  444.         foreach($ac3_coding_mode as $key => $value) {
  445.             $thisfile_ac3[$key] = $value;
  446.         }
  447.         switch ($thisfile_ac3_raw_bsi['acmod']) {
  448.             case 0:
  449.             case 1:
  450.                 $info['audio']['channelmode'] = 'mono';
  451.                 break;
  452.             case 3:
  453.             case 4:
  454.                 $info['audio']['channelmode'] = 'stereo';
  455.                 break;
  456.             default:
  457.                 $info['audio']['channelmode'] = 'surround';
  458.                 break;
  459.         }
  460.         $info['audio']['channels'] = $thisfile_ac3['num_channels'];
  461.  
  462.         $thisfile_ac3['lfe_enabled'] = $thisfile_ac3_raw_bsi['flags']['lfeon'];
  463.         if ($thisfile_ac3_raw_bsi['flags']['lfeon']) {
  464.             $info['audio']['channels'] .= '.1';
  465.         }
  466.  
  467.         $thisfile_ac3['channels_enabled'] = self::channelsEnabledLookup($thisfile_ac3_raw_bsi['acmod'], $thisfile_ac3_raw_bsi['flags']['lfeon']);
  468.         $thisfile_ac3['dialogue_normalization'] = '-'.$thisfile_ac3_raw_bsi['dialnorm'].'dB';
  469.  
  470.         return true;
  471.     }
  472.  
  473.     private function readHeaderBSI($length) {
  474.         $data = substr($this->AC3header['bsi'], $this->BSIoffset, $length);
  475.         $this->BSIoffset += $length;
  476.  
  477.         return bindec($data);
  478.     }
  479.  
  480.     public static function sampleRateCodeLookup($fscod) {
  481.         static $sampleRateCodeLookup = array(
  482.             0 => 48000,
  483.             1 => 44100,
  484.             2 => 32000,
  485.             3 => 'reserved' // If the reserved code is indicated, the decoder should not attempt to decode audio and should mute.
  486.         );
  487.         return (isset($sampleRateCodeLookup[$fscod]) ? $sampleRateCodeLookup[$fscod] : false);
  488.     }
  489.  
  490.     public static function sampleRateCodeLookup2($fscod2) {
  491.         static $sampleRateCodeLookup2 = array(
  492.             0 => 24000,
  493.             1 => 22050,
  494.             2 => 16000,
  495.             3 => 'reserved' // If the reserved code is indicated, the decoder should not attempt to decode audio and should mute.
  496.         );
  497.         return (isset($sampleRateCodeLookup2[$fscod2]) ? $sampleRateCodeLookup2[$fscod2] : false);
  498.     }
  499.  
  500.     public static function serviceTypeLookup($bsmod, $acmod) {
  501.         static $serviceTypeLookup = array();
  502.         if (empty($serviceTypeLookup)) {
  503.             for ($i = 0; $i <= 7; $i++) {
  504.                 $serviceTypeLookup[0][$i] = 'main audio service: complete main (CM)';
  505.                 $serviceTypeLookup[1][$i] = 'main audio service: music and effects (ME)';
  506.                 $serviceTypeLookup[2][$i] = 'associated service: visually impaired (VI)';
  507.                 $serviceTypeLookup[3][$i] = 'associated service: hearing impaired (HI)';
  508.                 $serviceTypeLookup[4][$i] = 'associated service: dialogue (D)';
  509.                 $serviceTypeLookup[5][$i] = 'associated service: commentary (C)';
  510.                 $serviceTypeLookup[6][$i] = 'associated service: emergency (E)';
  511.             }
  512.  
  513.             $serviceTypeLookup[7][1]      = 'associated service: voice over (VO)';
  514.             for ($i = 2; $i <= 7; $i++) {
  515.                 $serviceTypeLookup[7][$i] = 'main audio service: karaoke';
  516.             }
  517.         }
  518.         return (isset($serviceTypeLookup[$bsmod][$acmod]) ? $serviceTypeLookup[$bsmod][$acmod] : false);
  519.     }
  520.  
  521.     public static function audioCodingModeLookup($acmod) {
  522.         // array(channel configuration, # channels (not incl LFE), channel order)
  523.         static $audioCodingModeLookup = array (
  524.             0 => array('channel_config'=>'1+1', 'num_channels'=>2, 'channel_order'=>'Ch1,Ch2'),
  525.             1 => array('channel_config'=>'1/0', 'num_channels'=>1, 'channel_order'=>'C'),
  526.             2 => array('channel_config'=>'2/0', 'num_channels'=>2, 'channel_order'=>'L,R'),
  527.             3 => array('channel_config'=>'3/0', 'num_channels'=>3, 'channel_order'=>'L,C,R'),
  528.             4 => array('channel_config'=>'2/1', 'num_channels'=>3, 'channel_order'=>'L,R,S'),
  529.             5 => array('channel_config'=>'3/1', 'num_channels'=>4, 'channel_order'=>'L,C,R,S'),
  530.             6 => array('channel_config'=>'2/2', 'num_channels'=>4, 'channel_order'=>'L,R,SL,SR'),
  531.             7 => array('channel_config'=>'3/2', 'num_channels'=>5, 'channel_order'=>'L,C,R,SL,SR'),
  532.         );
  533.         return (isset($audioCodingModeLookup[$acmod]) ? $audioCodingModeLookup[$acmod] : false);
  534.     }
  535.  
  536.     public static function centerMixLevelLookup($cmixlev) {
  537.         static $centerMixLevelLookup;
  538.         if (empty($centerMixLevelLookup)) {
  539.             $centerMixLevelLookup = array(
  540.                 0 => pow(2, -3.0 / 6), // 0.707 (-3.0 dB)
  541.                 1 => pow(2, -4.5 / 6), // 0.595 (-4.5 dB)
  542.                 2 => pow(2, -6.0 / 6), // 0.500 (-6.0 dB)
  543.                 3 => 'reserved'
  544.             );
  545.         }
  546.         return (isset($centerMixLevelLookup[$cmixlev]) ? $centerMixLevelLookup[$cmixlev] : false);
  547.     }
  548.  
  549.     public static function surroundMixLevelLookup($surmixlev) {
  550.         static $surroundMixLevelLookup;
  551.         if (empty($surroundMixLevelLookup)) {
  552.             $surroundMixLevelLookup = array(
  553.                 0 => pow(2, -3.0 / 6),
  554.                 1 => pow(2, -6.0 / 6),
  555.                 2 => 0,
  556.                 3 => 'reserved'
  557.             );
  558.         }
  559.         return (isset($surroundMixLevelLookup[$surmixlev]) ? $surroundMixLevelLookup[$surmixlev] : false);
  560.     }
  561.  
  562.     public static function dolbySurroundModeLookup($dsurmod) {
  563.         static $dolbySurroundModeLookup = array(
  564.             0 => 'not indicated',
  565.             1 => 'Not Dolby Surround encoded',
  566.             2 => 'Dolby Surround encoded',
  567.             3 => 'reserved'
  568.         );
  569.         return (isset($dolbySurroundModeLookup[$dsurmod]) ? $dolbySurroundModeLookup[$dsurmod] : false);
  570.     }
  571.  
  572.     public static function channelsEnabledLookup($acmod, $lfeon) {
  573.         $lookup = array(
  574.             'ch1'=>(bool) ($acmod == 0),
  575.             'ch2'=>(bool) ($acmod == 0),
  576.             'left'=>(bool) ($acmod > 1),
  577.             'right'=>(bool) ($acmod > 1),
  578.             'center'=>(bool) ($acmod & 0x01),
  579.             'surround_mono'=>false,
  580.             'surround_left'=>false,
  581.             'surround_right'=>false,
  582.             'lfe'=>$lfeon);
  583.         switch ($acmod) {
  584.             case 4:
  585.             case 5:
  586.                 $lookup['surround_mono']  = true;
  587.                 break;
  588.             case 6:
  589.             case 7:
  590.                 $lookup['surround_left']  = true;
  591.                 $lookup['surround_right'] = true;
  592.                 break;
  593.         }
  594.         return $lookup;
  595.     }
  596.  
  597.     public static function heavyCompression($compre) {
  598.         // The first four bits indicate gain changes in 6.02dB increments which can be
  599.         // implemented with an arithmetic shift operation. The following four bits
  600.         // indicate linear gain changes, and require a 5-bit multiply.
  601.         // We will represent the two 4-bit fields of compr as follows:
  602.         //   X0 X1 X2 X3 . Y4 Y5 Y6 Y7
  603.         // The meaning of the X values is most simply described by considering X to represent a 4-bit
  604.         // signed integer with values from -8 to +7. The gain indicated by X is then (X + 1) * 6.02 dB. The
  605.         // following table shows this in detail.
  606.  
  607.         // Meaning of 4 msb of compr
  608.         //  7    +48.16 dB
  609.         //  6    +42.14 dB
  610.         //  5    +36.12 dB
  611.         //  4    +30.10 dB
  612.         //  3    +24.08 dB
  613.         //  2    +18.06 dB
  614.         //  1    +12.04 dB
  615.         //  0     +6.02 dB
  616.         // -1         0 dB
  617.         // -2     -6.02 dB
  618.         // -3    -12.04 dB
  619.         // -4    -18.06 dB
  620.         // -5    -24.08 dB
  621.         // -6    -30.10 dB
  622.         // -7    -36.12 dB
  623.         // -8    -42.14 dB
  624.  
  625.         $fourbit = str_pad(decbin(($compre & 0xF0) >> 4), 4, '0', STR_PAD_LEFT);
  626.         if ($fourbit{0} == '1') {
  627.             $log_gain = -8 + bindec(substr($fourbit, 1));
  628.         } else {
  629.             $log_gain = bindec(substr($fourbit, 1));
  630.         }
  631.         $log_gain = ($log_gain + 1) * getid3_lib::RGADamplitude2dB(2);
  632.  
  633.         // The value of Y is a linear representation of a gain change of up to -6 dB. Y is considered to
  634.         // be an unsigned fractional integer, with a leading value of 1, or: 0.1 Y4 Y5 Y6 Y7 (base 2). Y can
  635.         // represent values between 0.111112 (or 31/32) and 0.100002 (or 1/2). Thus, Y can represent gain
  636.         // changes from -0.28 dB to -6.02 dB.
  637.  
  638.         $lin_gain = (16 + ($compre & 0x0F)) / 32;
  639.  
  640.         // The combination of X and Y values allows compr to indicate gain changes from
  641.         //  48.16 - 0.28 = +47.89 dB, to
  642.         // -42.14 - 6.02 = -48.16 dB.
  643.  
  644.         return $log_gain - $lin_gain;
  645.     }
  646.  
  647.     public static function roomTypeLookup($roomtyp) {
  648.         static $roomTypeLookup = array(
  649.             0 => 'not indicated',
  650.             1 => 'large room, X curve monitor',
  651.             2 => 'small room, flat monitor',
  652.             3 => 'reserved'
  653.         );
  654.         return (isset($roomTypeLookup[$roomtyp]) ? $roomTypeLookup[$roomtyp] : false);
  655.     }
  656.  
  657.     public static function frameSizeLookup($frmsizecod, $fscod) {
  658.         // LSB is whether padding is used or not
  659.         $padding     = (bool) ($frmsizecod & 0x01);
  660.         $framesizeid =        ($frmsizecod & 0x3E) >> 1;
  661.  
  662.         static $frameSizeLookup = array();
  663.         if (empty($frameSizeLookup)) {
  664.             $frameSizeLookup = array (
  665.                 0  => array( 128,  138,  192),  //  32 kbps
  666.                 1  => array( 160,  174,  240),  //  40 kbps
  667.                 2  => array( 192,  208,  288),  //  48 kbps
  668.                 3  => array( 224,  242,  336),  //  56 kbps
  669.                 4  => array( 256,  278,  384),  //  64 kbps
  670.                 5  => array( 320,  348,  480),  //  80 kbps
  671.                 6  => array( 384,  416,  576),  //  96 kbps
  672.                 7  => array( 448,  486,  672),  // 112 kbps
  673.                 8  => array( 512,  556,  768),  // 128 kbps
  674.                 9  => array( 640,  696,  960),  // 160 kbps
  675.                 10 => array( 768,  834, 1152),  // 192 kbps
  676.                 11 => array( 896,  974, 1344),  // 224 kbps
  677.                 12 => array(1024, 1114, 1536),  // 256 kbps
  678.                 13 => array(1280, 1392, 1920),  // 320 kbps
  679.                 14 => array(1536, 1670, 2304),  // 384 kbps
  680.                 15 => array(1792, 1950, 2688),  // 448 kbps
  681.                 16 => array(2048, 2228, 3072),  // 512 kbps
  682.                 17 => array(2304, 2506, 3456),  // 576 kbps
  683.                 18 => array(2560, 2786, 3840)   // 640 kbps
  684.             );
  685.         }
  686.         if (($fscod == 1) && $padding) {
  687.             // frame lengths are padded by 1 word (16 bits) at 44100
  688.             $frameSizeLookup[$frmsizecod] += 2;
  689.         }
  690.         return (isset($frameSizeLookup[$framesizeid][$fscod]) ? $frameSizeLookup[$framesizeid][$fscod] : false);
  691.     }
  692.  
  693.     public static function bitrateLookup($frmsizecod) {
  694.         // LSB is whether padding is used or not
  695.         $padding     = (bool) ($frmsizecod & 0x01);
  696.         $framesizeid =        ($frmsizecod & 0x3E) >> 1;
  697.  
  698.         static $bitrateLookup = array(
  699.              0 =>  32000,
  700.              1 =>  40000,
  701.              2 =>  48000,
  702.              3 =>  56000,
  703.              4 =>  64000,
  704.              5 =>  80000,
  705.              6 =>  96000,
  706.              7 => 112000,
  707.              8 => 128000,
  708.              9 => 160000,
  709.             10 => 192000,
  710.             11 => 224000,
  711.             12 => 256000,
  712.             13 => 320000,
  713.             14 => 384000,
  714.             15 => 448000,
  715.             16 => 512000,
  716.             17 => 576000,
  717.             18 => 640000,
  718.         );
  719.         return (isset($bitrateLookup[$framesizeid]) ? $bitrateLookup[$framesizeid] : false);
  720.     }
  721.  
  722.     public static function blocksPerSyncFrame($numblkscod) {
  723.         static $blocksPerSyncFrameLookup = array(
  724.             0 => 1,
  725.             1 => 2,
  726.             2 => 3,
  727.             3 => 6,
  728.         );
  729.         return (isset($blocksPerSyncFrameLookup[$numblkscod]) ? $blocksPerSyncFrameLookup[$numblkscod] : false);
  730.     }
  731.  
  732.  
  733. }
  734.