www/plugins-dist/medias/lib/getid3/module.audio.ac3.php

   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 }