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