<?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);