File indexing completed on 2024-05-12 17:25:58

 <?php
 /////////////////////////////////////////////////////////////////
 /// getID3() by James Heinrich <info@getid3.org>               //
 //  available at http://getid3.sourceforge.net                 //
 //            or http://www.getid3.org                         //
 //          also https://github.com/JamesHeinrich/getID3       //
 /////////////////////////////////////////////////////////////////
 // See readme.txt for more details                             //
 /////////////////////////////////////////////////////////////////
 //                                                             //
 // module.audio.ac3.php                                        //
 // module for analyzing AC-3 (aka Dolby Digital) audio files   //
 // dependencies: NONE                                          //
 //                                                            ///
 /////////////////////////////////////////////////////////////////
 
 
 class getid3_ac3 extends getid3_handler
 {
     private $AC3header = array();
     private $BSIoffset = 0;
 
     const syncword = "\x0B\x77";
 
   public function Analyze() {
     $info = &$this->getid3->info;
 
     ///AH
     $info['ac3']['raw']['bsi'] = array();
     $thisfile_ac3              = &$info['ac3'];
     $thisfile_ac3_raw          = &$thisfile_ac3['raw'];
     $thisfile_ac3_raw_bsi      = &$thisfile_ac3_raw['bsi'];
 
 
     // http://www.atsc.org/standards/a_52a.pdf
 
     $info['fileformat'] = 'ac3';
 
     // An AC-3 serial coded audio bit stream is made up of a sequence of synchronization frames
     // Each synchronization frame contains 6 coded audio blocks (AB), each of which represent 256
     // new audio samples per channel. A synchronization information (SI) header at the beginning
     // of each frame contains information needed to acquire and maintain synchronization. A
     // bit stream information (BSI) header follows SI, and contains parameters describing the coded
     // audio service. The coded audio blocks may be followed by an auxiliary data (Aux) field. At the
     // end of each frame is an error check field that includes a CRC word for error detection. An
     // additional CRC word is located in the SI header, the use of which, by a decoder, is optional.
     //
     // syncinfo() | bsi() | AB0 | AB1 | AB2 | AB3 | AB4 | AB5 | Aux | CRC
 
     // syncinfo() {
     //   syncword    16
     //   crc1        16
     //   fscod        2
     //   frmsizecod   6
     // } /* end of syncinfo */
 
     $this->fseek($info['avdataoffset']);
     $this->AC3header['syncinfo'] = $this->fread(5);
 
     if (strpos($this->AC3header['syncinfo'], self::syncword) === 0) {
       $thisfile_ac3_raw['synchinfo']['synchword'] = self::syncword;
       $offset = 2;
     } else {
       if (!$this->isDependencyFor('matroska')) {
         unset($info['fileformat'], $info['ac3']);
         return $this->error('Expecting "'.getid3_lib::PrintHexBytes(self::syncword).'" at offset '.$info['avdataoffset'].', found "'.getid3_lib::PrintHexBytes(substr($this->AC3header['syncinfo'], 0, 2)).'"');
       }
       $offset = 0;
       $this->fseek(-2, SEEK_CUR);
     }
 
     $info['audio']['dataformat']   = 'ac3';
     $info['audio']['bitrate_mode'] = 'cbr';
     $info['audio']['lossless']     = false;
 
     $thisfile_ac3_raw['synchinfo']['crc1']       = getid3_lib::LittleEndian2Int(substr($this->AC3header['syncinfo'], $offset, 2));
     $ac3_synchinfo_fscod_frmsizecod              = getid3_lib::LittleEndian2Int(substr($this->AC3header['syncinfo'], ($offset + 2), 1));
     $thisfile_ac3_raw['synchinfo']['fscod']      = ($ac3_synchinfo_fscod_frmsizecod & 0xC0) >> 6;
     $thisfile_ac3_raw['synchinfo']['frmsizecod'] = ($ac3_synchinfo_fscod_frmsizecod & 0x3F);
 
     $thisfile_ac3['sample_rate'] = self::sampleRateCodeLookup($thisfile_ac3_raw['synchinfo']['fscod']);
     if ($thisfile_ac3_raw['synchinfo']['fscod'] <= 3) {
       $info['audio']['sample_rate'] = $thisfile_ac3['sample_rate'];
     }
 
     $thisfile_ac3['frame_length'] = self::frameSizeLookup($thisfile_ac3_raw['synchinfo']['frmsizecod'], $thisfile_ac3_raw['synchinfo']['fscod']);
     $thisfile_ac3['bitrate']      = self::bitrateLookup($thisfile_ac3_raw['synchinfo']['frmsizecod']);
     $info['audio']['bitrate'] = $thisfile_ac3['bitrate'];
 
     $this->AC3header['bsi'] = getid3_lib::BigEndian2Bin($this->fread(15));
     $ac3_bsi_offset = 0;
 
     $thisfile_ac3_raw_bsi['bsid'] = $this->readHeaderBSI(5);
     if ($thisfile_ac3_raw_bsi['bsid'] > 8) {
       // Decoders which can decode version 8 will thus be able to decode version numbers less than 8.
       // If this standard is extended by the addition of additional elements or features, a value of bsid greater than 8 will be used.
       // Decoders built to this version of the standard will not be able to decode versions with bsid greater than 8.
       $this->error('Bit stream identification is version '.$thisfile_ac3_raw_bsi['bsid'].', but getID3() only understands up to version 8');
         unset($info['ac3']);
       return false;
     }
 
     $thisfile_ac3_raw_bsi['bsmod'] = $this->readHeaderBSI(3);
     $thisfile_ac3_raw_bsi['acmod'] = $this->readHeaderBSI(3);
 
     $thisfile_ac3['service_type'] = self::serviceTypeLookup($thisfile_ac3_raw_bsi['bsmod'], $thisfile_ac3_raw_bsi['acmod']);
     $ac3_coding_mode = self::audioCodingModeLookup($thisfile_ac3_raw_bsi['acmod']);
     foreach($ac3_coding_mode as $key => $value) {
       $thisfile_ac3[$key] = $value;
     }
     switch ($thisfile_ac3_raw_bsi['acmod']) {
       case 0:
       case 1:
         $info['audio']['channelmode'] = 'mono';
         break;
       case 3:
       case 4:
         $info['audio']['channelmode'] = 'stereo';
         break;
       default:
         $info['audio']['channelmode'] = 'surround';
         break;
     }
     $info['audio']['channels'] = $thisfile_ac3['num_channels'];
 
     if ($thisfile_ac3_raw_bsi['acmod'] & 0x01) {
       // If the lsb of acmod is a 1, center channel is in use and cmixlev follows in the bit stream.
       $thisfile_ac3_raw_bsi['cmixlev'] = $this->readHeaderBSI(2);
       $thisfile_ac3['center_mix_level'] = self::centerMixLevelLookup($thisfile_ac3_raw_bsi['cmixlev']);
     }
 
     if ($thisfile_ac3_raw_bsi['acmod'] & 0x04) {
       // If the msb of acmod is a 1, surround channels are in use and surmixlev follows in the bit stream.
       $thisfile_ac3_raw_bsi['surmixlev'] = $this->readHeaderBSI(2);
       $thisfile_ac3['surround_mix_level'] = self::surroundMixLevelLookup($thisfile_ac3_raw_bsi['surmixlev']);
     }
 
     if ($thisfile_ac3_raw_bsi['acmod'] == 0x02) {
       // When operating in the two channel mode, this 2-bit code indicates whether or not the program has been encoded in Dolby Surround.
       $thisfile_ac3_raw_bsi['dsurmod'] = $this->readHeaderBSI(2);
       $thisfile_ac3['dolby_surround_mode'] = self::dolbySurroundModeLookup($thisfile_ac3_raw_bsi['dsurmod']);
     }
 
     $thisfile_ac3_raw_bsi['lfeon'] = (bool) $this->readHeaderBSI(1);
     $thisfile_ac3['lfe_enabled'] = $thisfile_ac3_raw_bsi['lfeon'];
     if ($thisfile_ac3_raw_bsi['lfeon']) {
       //$info['audio']['channels']++;
       $info['audio']['channels'] .= '.1';
     }
 
     $thisfile_ac3['channels_enabled'] = self::channelsEnabledLookup($thisfile_ac3_raw_bsi['acmod'], $thisfile_ac3_raw_bsi['lfeon']);
 
     // 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.
     $thisfile_ac3_raw_bsi['dialnorm'] = $this->readHeaderBSI(5);
     $thisfile_ac3['dialogue_normalization'] = '-'.$thisfile_ac3_raw_bsi['dialnorm'].'dB';
 
     $thisfile_ac3_raw_bsi['compre_flag'] = (bool) $this->readHeaderBSI(1);
     if ($thisfile_ac3_raw_bsi['compre_flag']) {
       $thisfile_ac3_raw_bsi['compr'] = $this->readHeaderBSI(8);
       $thisfile_ac3['heavy_compression'] = self::heavyCompression($thisfile_ac3_raw_bsi['compr']);
     }
 
     $thisfile_ac3_raw_bsi['langcode_flag'] = (bool) $this->readHeaderBSI(1);
     if ($thisfile_ac3_raw_bsi['langcode_flag']) {
       $thisfile_ac3_raw_bsi['langcod'] = $this->readHeaderBSI(8);
     }
 
     $thisfile_ac3_raw_bsi['audprodie'] = (bool) $this->readHeaderBSI(1);
     if ($thisfile_ac3_raw_bsi['audprodie']) {
       $thisfile_ac3_raw_bsi['mixlevel'] = $this->readHeaderBSI(5);
       $thisfile_ac3_raw_bsi['roomtyp']  = $this->readHeaderBSI(2);
 
       $thisfile_ac3['mixing_level'] = (80 + $thisfile_ac3_raw_bsi['mixlevel']).'dB';
       $thisfile_ac3['room_type']    = self::roomTypeLookup($thisfile_ac3_raw_bsi['roomtyp']);
     }
 
     if ($thisfile_ac3_raw_bsi['acmod'] == 0x00) {
       // If acmod is 0, then two completely independent program channels (dual mono)
       // are encoded into the bit stream, and are referenced as Ch1, Ch2. In this case,
       // a number of additional items are present in BSI or audblk to fully describe Ch2.
 
       // 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.
       $thisfile_ac3_raw_bsi['dialnorm2'] = $this->readHeaderBSI(5);
       $thisfile_ac3['dialogue_normalization2'] = '-'.$thisfile_ac3_raw_bsi['dialnorm2'].'dB';
 
       $thisfile_ac3_raw_bsi['compre_flag2'] = (bool) $this->readHeaderBSI(1);
       if ($thisfile_ac3_raw_bsi['compre_flag2']) {
         $thisfile_ac3_raw_bsi['compr2'] = $this->readHeaderBSI(8);
         $thisfile_ac3['heavy_compression2'] = self::heavyCompression($thisfile_ac3_raw_bsi['compr2']);
       }
 
       $thisfile_ac3_raw_bsi['langcode_flag2'] = (bool) $this->readHeaderBSI(1);
       if ($thisfile_ac3_raw_bsi['langcode_flag2']) {
         $thisfile_ac3_raw_bsi['langcod2'] = $this->readHeaderBSI(8);
       }
 
       $thisfile_ac3_raw_bsi['audprodie2'] = (bool) $this->readHeaderBSI(1);
       if ($thisfile_ac3_raw_bsi['audprodie2']) {
         $thisfile_ac3_raw_bsi['mixlevel2'] = $this->readHeaderBSI(5);
         $thisfile_ac3_raw_bsi['roomtyp2']  = $this->readHeaderBSI(2);
 
         $thisfile_ac3['mixing_level2'] = (80 + $thisfile_ac3_raw_bsi['mixlevel2']).'dB';
         $thisfile_ac3['room_type2']    = self::roomTypeLookup($thisfile_ac3_raw_bsi['roomtyp2']);
       }
 
     }
 
     $thisfile_ac3_raw_bsi['copyright'] = (bool) $this->readHeaderBSI(1);
 
     $thisfile_ac3_raw_bsi['original']  = (bool) $this->readHeaderBSI(1);
 
     $thisfile_ac3_raw_bsi['timecode1_flag'] = (bool) $this->readHeaderBSI(1);
     if ($thisfile_ac3_raw_bsi['timecode1_flag']) {
       $thisfile_ac3_raw_bsi['timecode1'] = $this->readHeaderBSI(14);
     }
 
     $thisfile_ac3_raw_bsi['timecode2_flag'] = (bool) $this->readHeaderBSI(1);
     if ($thisfile_ac3_raw_bsi['timecode2_flag']) {
       $thisfile_ac3_raw_bsi['timecode2'] = $this->readHeaderBSI(14);
     }
 
     $thisfile_ac3_raw_bsi['addbsi_flag'] = (bool) $this->readHeaderBSI(1);
     if ($thisfile_ac3_raw_bsi['addbsi_flag']) {
       $thisfile_ac3_raw_bsi['addbsi_length'] = $this->readHeaderBSI(6);
 
       $this->AC3header['bsi'] .= getid3_lib::BigEndian2Bin($this->fread($thisfile_ac3_raw_bsi['addbsi_length']));
 
       $thisfile_ac3_raw_bsi['addbsi_data'] = substr($this->AC3header['bsi'], $this->BSIoffset, $thisfile_ac3_raw_bsi['addbsi_length'] * 8);
       $this->BSIoffset += $thisfile_ac3_raw_bsi['addbsi_length'] * 8;
     }
 
     return true;
   }
 
   private function readHeaderBSI($length) {
     $data = substr($this->AC3header['bsi'], $this->BSIoffset, $length);
     $this->BSIoffset += $length;
 
     return bindec($data);
   }
 
   public static function sampleRateCodeLookup($fscod) {
     static $sampleRateCodeLookup = array(
       0 => 48000,
       1 => 44100,
       2 => 32000,
       3 => 'reserved' // If the reserved code is indicated, the decoder should not attempt to decode audio and should mute.
     );
     return (isset($sampleRateCodeLookup[$fscod]) ? $sampleRateCodeLookup[$fscod] : false);
   }
 
   public static function serviceTypeLookup($bsmod, $acmod) {
     static $serviceTypeLookup = array();
     if (empty($serviceTypeLookup)) {
       for ($i = 0; $i <= 7; $i++) {
         $serviceTypeLookup[0][$i] = 'main audio service: complete main (CM)';
         $serviceTypeLookup[1][$i] = 'main audio service: music and effects (ME)';
         $serviceTypeLookup[2][$i] = 'associated service: visually impaired (VI)';
         $serviceTypeLookup[3][$i] = 'associated service: hearing impaired (HI)';
         $serviceTypeLookup[4][$i] = 'associated service: dialogue (D)';
         $serviceTypeLookup[5][$i] = 'associated service: commentary (C)';
         $serviceTypeLookup[6][$i] = 'associated service: emergency (E)';
       }
 
       $serviceTypeLookup[7][1]      = 'associated service: voice over (VO)';
       for ($i = 2; $i <= 7; $i++) {
         $serviceTypeLookup[7][$i] = 'main audio service: karaoke';
       }
     }
     return (isset($serviceTypeLookup[$bsmod][$acmod]) ? $serviceTypeLookup[$bsmod][$acmod] : false);
   }
 
   public static function audioCodingModeLookup($acmod) {
     // array(channel configuration, # channels (not incl LFE), channel order)
     static $audioCodingModeLookup = array (
       0 => array('channel_config'=>'1+1', 'num_channels'=>2, 'channel_order'=>'Ch1,Ch2'),
       1 => array('channel_config'=>'1/0', 'num_channels'=>1, 'channel_order'=>'C'),
       2 => array('channel_config'=>'2/0', 'num_channels'=>2, 'channel_order'=>'L,R'),
       3 => array('channel_config'=>'3/0', 'num_channels'=>3, 'channel_order'=>'L,C,R'),
       4 => array('channel_config'=>'2/1', 'num_channels'=>3, 'channel_order'=>'L,R,S'),
       5 => array('channel_config'=>'3/1', 'num_channels'=>4, 'channel_order'=>'L,C,R,S'),
       6 => array('channel_config'=>'2/2', 'num_channels'=>4, 'channel_order'=>'L,R,SL,SR'),
       7 => array('channel_config'=>'3/2', 'num_channels'=>5, 'channel_order'=>'L,C,R,SL,SR'),
     );
     return (isset($audioCodingModeLookup[$acmod]) ? $audioCodingModeLookup[$acmod] : false);
   }
 
   public static function centerMixLevelLookup($cmixlev) {
     static $centerMixLevelLookup;
     if (empty($centerMixLevelLookup)) {
       $centerMixLevelLookup = array(
         0 => pow(2, -3.0 / 6), // 0.707 (-3.0 dB)
         1 => pow(2, -4.5 / 6), // 0.595 (-4.5 dB)
         2 => pow(2, -6.0 / 6), // 0.500 (-6.0 dB)
         3 => 'reserved'
       );
     }
     return (isset($centerMixLevelLookup[$cmixlev]) ? $centerMixLevelLookup[$cmixlev] : false);
   }
 
   public static function surroundMixLevelLookup($surmixlev) {
     static $surroundMixLevelLookup;
     if (empty($surroundMixLevelLookup)) {
       $surroundMixLevelLookup = array(
         0 => pow(2, -3.0 / 6),
         1 => pow(2, -6.0 / 6),
         2 => 0,
         3 => 'reserved'
       );
     }
     return (isset($surroundMixLevelLookup[$surmixlev]) ? $surroundMixLevelLookup[$surmixlev] : false);
   }
 
   public static function dolbySurroundModeLookup($dsurmod) {
     static $dolbySurroundModeLookup = array(
       0 => 'not indicated',
       1 => 'Not Dolby Surround encoded',
       2 => 'Dolby Surround encoded',
       3 => 'reserved'
     );
     return (isset($dolbySurroundModeLookup[$dsurmod]) ? $dolbySurroundModeLookup[$dsurmod] : false);
   }
 
   public static function channelsEnabledLookup($acmod, $lfeon) {
     $lookup = array(
       'ch1'=>(bool) ($acmod == 0),
       'ch2'=>(bool) ($acmod == 0),
       'left'=>(bool) ($acmod > 1),
       'right'=>(bool) ($acmod > 1),
       'center'=>(bool) ($acmod & 0x01),
       'surround_mono'=>false,
       'surround_left'=>false,
       'surround_right'=>false,
       'lfe'=>$lfeon);
     switch ($acmod) {
       case 4:
       case 5:
         $lookup['surround_mono']  = true;
         break;
       case 6:
       case 7:
         $lookup['surround_left']  = true;
         $lookup['surround_right'] = true;
         break;
     }
     return $lookup;
   }
 
   public static function heavyCompression($compre) {
     // The first four bits indicate gain changes in 6.02dB increments which can be
     // implemented with an arithmetic shift operation. The following four bits
     // indicate linear gain changes, and require a 5-bit multiply.
     // We will represent the two 4-bit fields of compr as follows:
     //   X0 X1 X2 X3 . Y4 Y5 Y6 Y7
     // The meaning of the X values is most simply described by considering X to represent a 4-bit
     // signed integer with values from -8 to +7. The gain indicated by X is then (X + 1) * 6.02 dB. The
     // following table shows this in detail.
 
     // Meaning of 4 msb of compr
     //  7    +48.16 dB
     //  6    +42.14 dB
     //  5    +36.12 dB
     //  4    +30.10 dB
     //  3    +24.08 dB
     //  2    +18.06 dB
     //  1    +12.04 dB
     //  0     +6.02 dB
     // -1         0 dB
     // -2     -6.02 dB
     // -3    -12.04 dB
     // -4    -18.06 dB
     // -5    -24.08 dB
     // -6    -30.10 dB
     // -7    -36.12 dB
     // -8    -42.14 dB
 
     $fourbit = str_pad(decbin(($compre & 0xF0) >> 4), 4, '0', STR_PAD_LEFT);
     if ($fourbit{0} == '1') {
       $log_gain = -8 + bindec(substr($fourbit, 1));
     } else {
       $log_gain = bindec(substr($fourbit, 1));
     }
     $log_gain = ($log_gain + 1) * getid3_lib::RGADamplitude2dB(2);
 
     // The value of Y is a linear representation of a gain change of up to -6 dB. Y is considered to
     // be an unsigned fractional integer, with a leading value of 1, or: 0.1 Y4 Y5 Y6 Y7 (base 2). Y can
     // represent values between 0.111112 (or 31/32) and 0.100002 (or 1/2). Thus, Y can represent gain
     // changes from -0.28 dB to -6.02 dB.
 
     $lin_gain = (16 + ($compre & 0x0F)) / 32;
 
     // The combination of X and Y values allows compr to indicate gain changes from
     //  48.16 - 0.28 = +47.89 dB, to
     // -42.14 - 6.02 = -48.16 dB.
 
     return $log_gain - $lin_gain;
   }
 
   public static function roomTypeLookup($roomtyp) {
     static $roomTypeLookup = array(
       0 => 'not indicated',
       1 => 'large room, X curve monitor',
       2 => 'small room, flat monitor',
       3 => 'reserved'
     );
     return (isset($roomTypeLookup[$roomtyp]) ? $roomTypeLookup[$roomtyp] : false);
   }
 
   public static function frameSizeLookup($frmsizecod, $fscod) {
     $padding     = (bool) ($frmsizecod % 2);
     $framesizeid =   floor($frmsizecod / 2);
 
     static $frameSizeLookup = array();
     if (empty($frameSizeLookup)) {
       $frameSizeLookup = array (
         0  => array(128, 138, 192),
         1  => array(40, 160, 174, 240),
         2  => array(48, 192, 208, 288),
         3  => array(56, 224, 242, 336),
         4  => array(64, 256, 278, 384),
         5  => array(80, 320, 348, 480),
         6  => array(96, 384, 416, 576),
         7  => array(112, 448, 486, 672),
         8  => array(128, 512, 556, 768),
         9  => array(160, 640, 696, 960),
         10 => array(192, 768, 834, 1152),
         11 => array(224, 896, 974, 1344),
         12 => array(256, 1024, 1114, 1536),
         13 => array(320, 1280, 1392, 1920),
         14 => array(384, 1536, 1670, 2304),
         15 => array(448, 1792, 1950, 2688),
         16 => array(512, 2048, 2228, 3072),
         17 => array(576, 2304, 2506, 3456),
         18 => array(640, 2560, 2786, 3840)
       );
     }
     if (($fscod == 1) && $padding) {
       // frame lengths are padded by 1 word (16 bits) at 44100
       $frameSizeLookup[$frmsizecod] += 2;
     }
     return (isset($frameSizeLookup[$framesizeid][$fscod]) ? $frameSizeLookup[$framesizeid][$fscod] : false);
   }
 
   public static function bitrateLookup($frmsizecod) {
     $framesizeid =   floor($frmsizecod / 2);
 
     static $bitrateLookup = array(
       0  => 32000,
       1  => 40000,
       2  => 48000,
       3  => 56000,
       4  => 64000,
       5  => 80000,
       6  => 96000,
       7  => 112000,
       8  => 128000,
       9  => 160000,
       10 => 192000,
       11 => 224000,
       12 => 256000,
       13 => 320000,
       14 => 384000,
       15 => 448000,
       16 => 512000,
       17 => 576000,
       18 => 640000
     );
     return (isset($bitrateLookup[$framesizeid]) ? $bitrateLookup[$framesizeid] : false);
   }
 
 
 }