Viewing file: module.audio.ac3.php (18.56 KB) -rw-rw-rw- Select action/file-type: (+) | (+) | (+) | Code (+) | Session (+) | (+) | SDB (+) | (+) | (+) | (+) | (+) | (+) |
<?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); }
}
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