<?php
/////////////////////////////////////////////////////////////////
/// getID3() by James Heinrich <info@getid3.org>               //
//  available at http://getid3.sourceforge.net                ///
//            or http://www.getid3.org                        ///
/////////////////////////////////////////////////////////////////
//                                                             //
// getid3.aac.php - part of getID3()                           //
// See getid3.readme.txt for more details                      //
//                                                             //
/////////////////////////////////////////////////////////////////

function getAACADIFheaderFilepointer(&$fd, &$ThisFileInfo) {
	$ThisFileInfo['fileformat']          = 'aac';
	$ThisFileInfo['audio']['dataformat'] = 'aac';
	$ThisFileInfo['audio']['lossless']   = false;

	fseek($fd, $ThisFileInfo['avdataoffset'], SEEK_SET);
	$AACheader = fread($fd, 1024);
	$offset    = 0;

	if (substr($AACheader, 0, 4) == 'ADIF') {

		// http://faac.sourceforge.net/wiki/index.php?page=ADIF

		// http://libmpeg.org/mpeg4/doc/w2203tfs.pdf
		// adif_header() {
		//     adif_id                                32
		//     copyright_id_present                    1
		//     if( copyright_id_present )
		//         copyright_id                       72
		//     original_copy                           1
		//     home                                    1
		//     bitstream_type                          1
		//     bitrate                                23
		//     num_program_config_elements             4
		//     for (i = 0; i < num_program_config_elements + 1; i++ ) {
		//         if( bitstream_type == '0' )
		//             adif_buffer_fullness           20
		//         program_config_element()
		//     }
		// }

		$AACheaderBitstream = BigEndian2Bin($AACheader);
		$bitoffset          = 0;

		$ThisFileInfo['aac']['header_type']                   = 'ADIF';
		$bitoffset += 32;
		$ThisFileInfo['aac']['header']['mpeg_version']        = 4;

		$ThisFileInfo['aac']['header']['copyright']           = (bool) (substr($AACheaderBitstream, $bitoffset, 1) == '1');
		$bitoffset += 1;
		if ($ThisFileInfo['aac']['header']['copyright']) {
			$ThisFileInfo['aac']['header']['copyright_id']    = Bin2String(substr($AACheaderBitstream, $bitoffset, 72));
			$bitoffset += 72;
		}
		$ThisFileInfo['aac']['header']['original_copy']       = (bool) (substr($AACheaderBitstream, $bitoffset, 1) == '1');
		$bitoffset += 1;
		$ThisFileInfo['aac']['header']['home']                = (bool) (substr($AACheaderBitstream, $bitoffset, 1) == '1');
		$bitoffset += 1;
		$ThisFileInfo['aac']['header']['is_vbr']              = (bool) (substr($AACheaderBitstream, $bitoffset, 1) == '1');
		$bitoffset += 1;
		if ($ThisFileInfo['aac']['header']['is_vbr']) {
			$ThisFileInfo['audio']['bitrate_mode']            = 'vbr';
			$ThisFileInfo['aac']['header']['bitrate_max']     = Bin2Dec(substr($AACheaderBitstream, $bitoffset, 23));
			$bitoffset += 23;
		} else {
			$ThisFileInfo['audio']['bitrate_mode']            = 'cbr';
			$ThisFileInfo['aac']['header']['bitrate']         = Bin2Dec(substr($AACheaderBitstream, $bitoffset, 23));
			$bitoffset += 23;
			$ThisFileInfo['audio']['bitrate']                 = $ThisFileInfo['aac']['header']['bitrate'];
		}
		if ($ThisFileInfo['audio']['bitrate'] == 0) {
			$ThisFileInfo['error'] .= "\n".'Corrupt AAC file: bitrate_audio == zero';
			return false;
		}
		$ThisFileInfo['aac']['header']['num_program_configs'] = 1 + Bin2Dec(substr($AACheaderBitstream, $bitoffset, 4));
		$bitoffset += 4;

		for ($i = 0; $i < $ThisFileInfo['aac']['header']['num_program_configs']; $i++) {
			// http://www.audiocoding.com/wiki/index.php?page=program_config_element

			// buffer_fullness                       20

			// element_instance_tag                   4
			// object_type                            2
			// sampling_frequency_index               4
			// num_front_channel_elements             4
			// num_side_channel_elements              4
			// num_back_channel_elements              4
			// num_lfe_channel_elements               2
			// num_assoc_data_elements                3
			// num_valid_cc_elements                  4
			// mono_mixdown_present                   1
			// mono_mixdown_element_number            4   if mono_mixdown_present == 1
			// stereo_mixdown_present                 1
			// stereo_mixdown_element_number          4   if stereo_mixdown_present == 1
			// matrix_mixdown_idx_present             1
			// matrix_mixdown_idx                     2   if matrix_mixdown_idx_present == 1
			// pseudo_surround_enable                 1   if matrix_mixdown_idx_present == 1
			// for (i = 0; i < num_front_channel_elements; i++) {
			//     front_element_is_cpe[i]            1
			//     front_element_tag_select[i]        4
			// }
			// for (i = 0; i < num_side_channel_elements; i++) {
			//     side_element_is_cpe[i]             1
			//     side_element_tag_select[i]         4
			// }
			// for (i = 0; i < num_back_channel_elements; i++) {
			//     back_element_is_cpe[i]             1
			//     back_element_tag_select[i]         4
			// }
			// for (i = 0; i < num_lfe_channel_elements; i++) {
			//     lfe_element_tag_select[i]          4
			// }
			// for (i = 0; i < num_assoc_data_elements; i++) {
			//     assoc_data_element_tag_select[i]   4
			// }
			// for (i = 0; i < num_valid_cc_elements; i++) {
			//     cc_element_is_ind_sw[i]            1
			//     valid_cc_element_tag_select[i]     4
			// }
			// byte_alignment()                       VAR
			// comment_field_bytes                    8
			// for (i = 0; i < comment_field_bytes; i++) {
			//     comment_field_data[i]              8
			// }

			if (!$ThisFileInfo['aac']['header']['is_vbr']) {
				$ThisFileInfo['aac']['program_configs'][$i]['buffer_fullness']        = Bin2Dec(substr($AACheaderBitstream, $bitoffset, 20));
				$bitoffset += 20;
			}
			$ThisFileInfo['aac']['program_configs'][$i]['element_instance_tag']       = Bin2Dec(substr($AACheaderBitstream, $bitoffset, 4));
			$bitoffset += 4;
			$ThisFileInfo['aac']['program_configs'][$i]['object_type']                = Bin2Dec(substr($AACheaderBitstream, $bitoffset, 2));
			$bitoffset += 2;
			$ThisFileInfo['aac']['program_configs'][$i]['sampling_frequency_index']   = Bin2Dec(substr($AACheaderBitstream, $bitoffset, 4));
			$bitoffset += 4;
			$ThisFileInfo['aac']['program_configs'][$i]['num_front_channel_elements'] = Bin2Dec(substr($AACheaderBitstream, $bitoffset, 4));
			$bitoffset += 4;
			$ThisFileInfo['aac']['program_configs'][$i]['num_side_channel_elements']  = Bin2Dec(substr($AACheaderBitstream, $bitoffset, 4));
			$bitoffset += 4;
			$ThisFileInfo['aac']['program_configs'][$i]['num_back_channel_elements']  = Bin2Dec(substr($AACheaderBitstream, $bitoffset, 4));
			$bitoffset += 4;
			$ThisFileInfo['aac']['program_configs'][$i]['num_lfe_channel_elements']   = Bin2Dec(substr($AACheaderBitstream, $bitoffset, 2));
			$bitoffset += 2;
			$ThisFileInfo['aac']['program_configs'][$i]['num_assoc_data_elements']    = Bin2Dec(substr($AACheaderBitstream, $bitoffset, 3));
			$bitoffset += 3;
			$ThisFileInfo['aac']['program_configs'][$i]['num_valid_cc_elements']      = Bin2Dec(substr($AACheaderBitstream, $bitoffset, 4));
			$bitoffset += 4;
			$ThisFileInfo['aac']['program_configs'][$i]['mono_mixdown_present']       = (bool) Bin2Dec(substr($AACheaderBitstream, $bitoffset, 1));
			$bitoffset += 1;
			if ($ThisFileInfo['aac']['program_configs'][$i]['mono_mixdown_present']) {
				$ThisFileInfo['aac']['program_configs'][$i]['mono_mixdown_element_number']    = Bin2Dec(substr($AACheaderBitstream, $bitoffset, 4));
				$bitoffset += 4;
			}
			$ThisFileInfo['aac']['program_configs'][$i]['stereo_mixdown_present']             = (bool) Bin2Dec(substr($AACheaderBitstream, $bitoffset, 1));
			$bitoffset += 1;
			if ($ThisFileInfo['aac']['program_configs'][$i]['stereo_mixdown_present']) {
				$ThisFileInfo['aac']['program_configs'][$i]['stereo_mixdown_element_number']  = Bin2Dec(substr($AACheaderBitstream, $bitoffset, 4));
				$bitoffset += 4;
			}
			$ThisFileInfo['aac']['program_configs'][$i]['matrix_mixdown_idx_present']         = (bool) Bin2Dec(substr($AACheaderBitstream, $bitoffset, 1));
			$bitoffset += 1;
			if ($ThisFileInfo['aac']['program_configs'][$i]['matrix_mixdown_idx_present']) {
				$ThisFileInfo['aac']['program_configs'][$i]['matrix_mixdown_idx']             = Bin2Dec(substr($AACheaderBitstream, $bitoffset, 2));
				$bitoffset += 2;
				$ThisFileInfo['aac']['program_configs'][$i]['pseudo_surround_enable']         = (bool) Bin2Dec(substr($AACheaderBitstream, $bitoffset, 1));
				$bitoffset += 1;
			}
			for ($j = 0; $j < $ThisFileInfo['aac']['program_configs'][$i]['num_front_channel_elements']; $j++) {
				$ThisFileInfo['aac']['program_configs'][$i]['front_element_is_cpe'][$j]     = (bool) Bin2Dec(substr($AACheaderBitstream, $bitoffset, 1));
				$bitoffset += 1;
				$ThisFileInfo['aac']['program_configs'][$i]['front_element_tag_select'][$j] = Bin2Dec(substr($AACheaderBitstream, $bitoffset, 4));
				$bitoffset += 4;
			}
			for ($j = 0; $j < $ThisFileInfo['aac']['program_configs'][$i]['num_side_channel_elements']; $j++) {
				$ThisFileInfo['aac']['program_configs'][$i]['side_element_is_cpe'][$j]     = (bool) Bin2Dec(substr($AACheaderBitstream, $bitoffset, 1));
				$bitoffset += 1;
				$ThisFileInfo['aac']['program_configs'][$i]['side_element_tag_select'][$j] = Bin2Dec(substr($AACheaderBitstream, $bitoffset, 4));
				$bitoffset += 4;
			}
			for ($j = 0; $j < $ThisFileInfo['aac']['program_configs'][$i]['num_back_channel_elements']; $j++) {
				$ThisFileInfo['aac']['program_configs'][$i]['back_element_is_cpe'][$j]     = (bool) Bin2Dec(substr($AACheaderBitstream, $bitoffset, 1));
				$bitoffset += 1;
				$ThisFileInfo['aac']['program_configs'][$i]['back_element_tag_select'][$j] = Bin2Dec(substr($AACheaderBitstream, $bitoffset, 4));
				$bitoffset += 4;
			}
			for ($j = 0; $j < $ThisFileInfo['aac']['program_configs'][$i]['num_lfe_channel_elements']; $j++) {
				$ThisFileInfo['aac']['program_configs'][$i]['lfe_element_tag_select'][$j] = Bin2Dec(substr($AACheaderBitstream, $bitoffset, 4));
				$bitoffset += 4;
			}
			for ($j = 0; $j < $ThisFileInfo['aac']['program_configs'][$i]['num_assoc_data_elements']; $j++) {
				$ThisFileInfo['aac']['program_configs'][$i]['assoc_data_element_tag_select'][$j] = Bin2Dec(substr($AACheaderBitstream, $bitoffset, 4));
				$bitoffset += 4;
			}
			for ($j = 0; $j < $ThisFileInfo['aac']['program_configs'][$i]['num_valid_cc_elements']; $j++) {
				$ThisFileInfo['aac']['program_configs'][$i]['cc_element_is_ind_sw'][$j]          = (bool) Bin2Dec(substr($AACheaderBitstream, $bitoffset, 1));
				$bitoffset += 1;
				$ThisFileInfo['aac']['program_configs'][$i]['valid_cc_element_tag_select'][$j]   = Bin2Dec(substr($AACheaderBitstream, $bitoffset, 4));
				$bitoffset += 4;
			}

			$bitoffset = ceil($bitoffset / 8) * 8;

			$ThisFileInfo['aac']['program_configs'][$i]['comment_field_bytes'] = Bin2Dec(substr($AACheaderBitstream, $bitoffset, 8));
			$bitoffset += 8;
			$ThisFileInfo['aac']['program_configs'][$i]['comment_field']       = Bin2String(substr($AACheaderBitstream, $bitoffset, 8 * $ThisFileInfo['aac']['program_configs'][$i]['comment_field_bytes']));
			$bitoffset += 8 * $ThisFileInfo['aac']['program_configs'][$i]['comment_field_bytes'];


			$ThisFileInfo['aac']['header']['profile_text']                      = AACprofileLookup($ThisFileInfo['aac']['program_configs'][$i]['object_type'], $ThisFileInfo['aac']['header']['mpeg_version']);
			$ThisFileInfo['aac']['program_configs'][$i]['sampling_frequency']   = AACsampleRateLookup($ThisFileInfo['aac']['program_configs'][$i]['sampling_frequency_index']);
			$ThisFileInfo['audio']['sample_rate']                               = $ThisFileInfo['aac']['program_configs'][$i]['sampling_frequency'];
			$ThisFileInfo['audio']['channels']                                  = AACchannelCountCalculate($ThisFileInfo['aac']['program_configs'][$i]);
			if ($ThisFileInfo['aac']['program_configs'][$i]['comment_field']) {
				$ThisFileInfo['comments']['comment'][]                   = $ThisFileInfo['aac']['program_configs'][$i]['comment_field'];
			}
		}
		$ThisFileInfo['playtime_seconds'] = (($ThisFileInfo['avdataend'] - $ThisFileInfo['avdataoffset']) * 8) / $ThisFileInfo['audio']['bitrate'];

		return true;

	} else {

		unset($ThisFileInfo['fileformat']);
		unset($ThisFileInfo['aac']);
		$ThisFileInfo['error'] .= "\n".'AAC-ADIF synch not found at offset '.$ThisFileInfo['avdataoffset'].' (expected "ADIF", found "'.substr($AACheader, 0, 4).'" instead)';
		return false;

	}

}


function getAACADTSheaderFilepointer(&$fd, &$ThisFileInfo, $MaxFramesToScan=1000000, $ReturnExtendedInfo=false) {
	// based loosely on code from AACfile by Jurgen Faul
	// jfaul@gmx.de     http://jfaul.de/atl


	// http://faac.sourceforge.net/wiki/index.php?page=ADTS

	// * ADTS Fixed Header: these don't change from frame to frame
	// syncword                                       12    always: '111111111111'
	// ID                                              1    0: MPEG-4, 1: MPEG-2
	// layer                                           2    always: '00'
	// protection_absent                               1
	// profile                                         2
	// sampling_frequency_index                        4
	// private_bit                                     1
	// channel_configuration                           3
	// original/copy                                   1
	// home                                            1
	// emphasis                                        2    only if ID == 0 (ie MPEG-4)

	// * ADTS Variable Header: these can change from frame to frame
	// copyright_identification_bit                    1
	// copyright_identification_start                  1
	// aac_frame_length                               13    length of the frame including header (in bytes)
	// adts_buffer_fullness                           11    0x7FF indicates VBR
	// no_raw_data_blocks_in_frame                     2

	// * ADTS Error check
	// crc_check                                      16    only if protection_absent == 0

	$byteoffset  = 0;
	$framenumber = 0;

	// Init bit pattern array
	static $decbin = array();

	// Populate $bindec
	for ($i = 0; $i < 256; $i++) {
		$decbin[chr($i)] = str_pad(decbin($i), 8, '0', STR_PAD_LEFT);
	}

	// used to calculate bitrate below
	static $BitrateCache = array();


	while (true) {
		// breaks out when end-of-file encountered, or invalid data found,
		// or MaxFramesToScan frames have been scanned

		fseek($fd, $byteoffset, SEEK_SET);

		// First get substring
		$substring = fread($fd, 10);
		$substringlength = strlen($substring);
		if ($substringlength != 10) {
			$ThisFileInfo['error'] .= "\n".'Failed to read 10 bytes at offset '.(ftell($fd) - $substringlength).' (only read '.$substringlength.' bytes)';
			return false;
		}

		// Initialise $AACheaderBitstream
		$AACheaderBitstream = '';

		// Loop thru substring chars
		for ($i = 0; $i < 10; $i++) {
			$AACheaderBitstream .= $decbin[$substring{$i}];
		}

		$bitoffset = 0;

		$synctest = bindec(substr($AACheaderBitstream, $bitoffset, 12));

		$bitoffset += 12;
		if ($synctest != 0x0FFF) {
			$ThisFileInfo['error'] .= "\n".'Synch pattern (0x0FFF) not found at offset '.(ftell($fd) - 10).' (found 0x0'.strtoupper(dechex($synctest)).' instead)';
			if ($ThisFileInfo['fileformat'] == 'aac') {
				return true;
			}
			return false;
		}

		// Gather info for first frame only - this takes time to do 1000 times!
		if ($framenumber > 0) {

			if (!$AACheaderBitstream[$bitoffset]) {

				// MPEG-4
				$bitoffset += 20;

			} else {

				// MPEG-2
				$bitoffset += 18;

			}

		} else {

			$ThisFileInfo['aac']['header_type']                      = 'ADTS';
			$ThisFileInfo['aac']['header']['synch']                  = $synctest;
			$ThisFileInfo['fileformat']                              = 'aac';
			$ThisFileInfo['audio']['dataformat']                     = 'aac';

			$ThisFileInfo['aac']['header']['mpeg_version']           = ((substr($AACheaderBitstream, $bitoffset, 1) == '0') ? 4 : 2);
			$bitoffset += 1;
			$ThisFileInfo['aac']['header']['layer']                  = Bin2Dec(substr($AACheaderBitstream, $bitoffset, 2));
			$bitoffset += 2;
			if ($ThisFileInfo['aac']['header']['layer'] != 0) {
				$ThisFileInfo['error'] .= "\n".'Layer error - expected 0x00, found 0x'.dechex($ThisFileInfo['aac']['header']['layer']).' instead';
				return false;
			}
			$ThisFileInfo['aac']['header']['crc_present']            = ((substr($AACheaderBitstream, $bitoffset, 1) == '0') ? true : false);
			$bitoffset += 1;
			$ThisFileInfo['aac']['header']['profile_id']             = Bin2Dec(substr($AACheaderBitstream, $bitoffset, 2));
			$bitoffset += 2;
			$ThisFileInfo['aac']['header']['profile_text']           = AACprofileLookup($ThisFileInfo['aac']['header']['profile_id'], $ThisFileInfo['aac']['header']['mpeg_version']);

			$ThisFileInfo['aac']['header']['sample_frequency_index'] = Bin2Dec(substr($AACheaderBitstream, $bitoffset, 4));
			$bitoffset += 4;
			$ThisFileInfo['aac']['header']['sample_frequency']       = AACsampleRateLookup($ThisFileInfo['aac']['header']['sample_frequency_index']);
			if ($ThisFileInfo['aac']['header']['sample_frequency'] == 0) {
				$ThisFileInfo['error'] .= "\n".'Corrupt AAC file: sample_frequency == zero';
				return false;
			}
			$ThisFileInfo['audio']['sample_rate']                    = $ThisFileInfo['aac']['header']['sample_frequency'];

			$ThisFileInfo['aac']['header']['private']                = (bool) Bin2Dec(substr($AACheaderBitstream, $bitoffset, 1));
			$bitoffset += 1;
			$ThisFileInfo['aac']['header']['channel_configuration']  = Bin2Dec(substr($AACheaderBitstream, $bitoffset, 3));
			$bitoffset += 3;
			$ThisFileInfo['audio']['channels']                       = $ThisFileInfo['aac']['header']['channel_configuration'];
			$ThisFileInfo['aac']['header']['original']               = (bool) Bin2Dec(substr($AACheaderBitstream, $bitoffset, 1));
			$bitoffset += 1;
			$ThisFileInfo['aac']['header']['home']                   = (bool) Bin2Dec(substr($AACheaderBitstream, $bitoffset, 1));
			$bitoffset += 1;

			if ($ThisFileInfo['aac']['header']['mpeg_version'] == 4) {
				$ThisFileInfo['aac']['header']['emphasis']           = Bin2Dec(substr($AACheaderBitstream, $bitoffset, 2));
				$bitoffset += 2;
			}

			if ($ReturnExtendedInfo) {

				$ThisFileInfo['aac'][$framenumber]['copyright_id_bit']   = (bool) Bin2Dec(substr($AACheaderBitstream, $bitoffset, 1));
				$bitoffset += 1;
				$ThisFileInfo['aac'][$framenumber]['copyright_id_start'] = (bool) Bin2Dec(substr($AACheaderBitstream, $bitoffset, 1));
				$bitoffset += 1;

			} else {

				$bitoffset += 2;

			}

		}

		$FrameLength = bindec(substr($AACheaderBitstream, $bitoffset, 13));

		if (!isset($BitrateCache[$FrameLength])) {
			$BitrateCache[$FrameLength] = ($ThisFileInfo['aac']['header']['sample_frequency'] / 1024) * $FrameLength * 8;
		}
		safe_inc($ThisFileInfo['aac']['bitrate_distribution'][$BitrateCache[$FrameLength]]);

		$ThisFileInfo['aac'][$framenumber]['aac_frame_length']     = $FrameLength;
		$bitoffset += 13;
		$ThisFileInfo['aac'][$framenumber]['adts_buffer_fullness'] = bindec(substr($AACheaderBitstream, $bitoffset, 11));
		$bitoffset += 11;
		if ($ThisFileInfo['aac'][$framenumber]['adts_buffer_fullness'] == 0x07FF) {
			$ThisFileInfo['audio']['bitrate_mode'] = 'vbr';
		} else {
			$ThisFileInfo['audio']['bitrate_mode'] = 'cbr';
		}
		$ThisFileInfo['aac'][$framenumber]['num_raw_data_blocks']  = bindec(substr($AACheaderBitstream, $bitoffset, 2));
		$bitoffset += 2;

		if ($ThisFileInfo['aac']['header']['crc_present']) {
			//$ThisFileInfo['aac'][$framenumber]['crc']              = bindec(substr($AACheaderBitstream, $bitoffset, 16));
			$bitoffset += 16;
		}

		if (!$ReturnExtendedInfo) {
			unset($ThisFileInfo['aac'][$framenumber]);
		}

		$byteoffset += $FrameLength;
		if ((++$framenumber < $MaxFramesToScan) && (($byteoffset + 10) < $ThisFileInfo['avdataend'])) {

			// keep scanning

		} else {

			$ThisFileInfo['aac']['frames']    = $framenumber;
			$ThisFileInfo['playtime_seconds'] = ($ThisFileInfo['avdataend'] / $byteoffset) * (($framenumber * 1024) / $ThisFileInfo['aac']['header']['sample_frequency']);  // (1 / % of file scanned) * (samples / (samples/sec)) = seconds
			if ($ThisFileInfo['playtime_seconds'] == 0) {
				$ThisFileInfo['error'] .= "\n".'Corrupt AAC file: playtime_seconds == zero';
				return false;
			}
			$ThisFileInfo['audio']['bitrate']    = (($ThisFileInfo['avdataend'] - $ThisFileInfo['avdataoffset']) * 8) / $ThisFileInfo['playtime_seconds'];
			ksort($ThisFileInfo['aac']['bitrate_distribution']);

			return true;

		}
	}
	// should never get here.
}

function AACsampleRateLookup($samplerateid) {
	static $AACsampleRateLookup = array();
	if (empty($AACsampleRateLookup)) {
		$AACsampleRateLookup[0]  = 96000;
		$AACsampleRateLookup[1]  = 88200;
		$AACsampleRateLookup[2]  = 64000;
		$AACsampleRateLookup[3]  = 48000;
		$AACsampleRateLookup[4]  = 44100;
		$AACsampleRateLookup[5]  = 32000;
		$AACsampleRateLookup[6]  = 24000;
		$AACsampleRateLookup[7]  = 22050;
		$AACsampleRateLookup[8]  = 16000;
		$AACsampleRateLookup[9]  = 12000;
		$AACsampleRateLookup[10] = 11025;
		$AACsampleRateLookup[11] = 8000;
		$AACsampleRateLookup[12] = 0;
		$AACsampleRateLookup[13] = 0;
		$AACsampleRateLookup[14] = 0;
		$AACsampleRateLookup[15] = 0;
	}
	return (isset($AACsampleRateLookup[$samplerateid]) ? $AACsampleRateLookup[$samplerateid] : 'invalid');
}

function AACprofileLookup($profileid, $mpegversion) {
	static $AACprofileLookup = array();
	if (empty($AACprofileLookup)) {
		$AACprofileLookup[2][0]  = 'Main profile';
		$AACprofileLookup[2][1]  = 'Low Complexity profile (LC)';
		$AACprofileLookup[2][2]  = 'Scalable Sample Rate profile (SSR)';
		$AACprofileLookup[2][3]  = '(reserved)';
		$AACprofileLookup[4][0]  = 'AAC_MAIN';
		$AACprofileLookup[4][1]  = 'AAC_LC';
		$AACprofileLookup[4][2]  = 'AAC_SSR';
		$AACprofileLookup[4][3]  = 'AAC_LTP';
	}
	return (isset($AACprofileLookup[$mpegversion][$profileid]) ? $AACprofileLookup[$mpegversion][$profileid] : 'invalid');
}

function AACchannelCountCalculate($program_configs) {
	$channels = 0;
	for ($i = 0; $i < $program_configs['num_front_channel_elements']; $i++) {
		$channels++;
		if ($program_configs['front_element_is_cpe'][$i]) {
			// each front element is channel pair (CPE = Channel Pair Element)
			$channels++;
		}
	}
	for ($i = 0; $i < $program_configs['num_side_channel_elements']; $i++) {
		$channels++;
		if ($program_configs['side_element_is_cpe'][$i]) {
			// each side element is channel pair (CPE = Channel Pair Element)
			$channels++;
		}
	}
	for ($i = 0; $i < $program_configs['num_back_channel_elements']; $i++) {
		$channels++;
		if ($program_configs['back_element_is_cpe'][$i]) {
			// each back element is channel pair (CPE = Channel Pair Element)
			$channels++;
		}
	}
	for ($i = 0; $i < $program_configs['num_lfe_channel_elements']; $i++) {
		$channels++;
	}
	return $channels;
}

?>