--- /dev/null
+<?php
+/////////////////////////////////////////////////////////////////
+/// getID3() by James Heinrich <info@getid3.org> //
+// available at http://getid3.sourceforge.net //
+// or http://www.getid3.org //
+/////////////////////////////////////////////////////////////////
+// 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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