name : module.audio.aac.php <?php ///////////////////////////////////////////////////////////////// /// getID3() by James Heinrich <info@getid3.org> // // available at https://github.com/JamesHeinrich/getID3 // // or https://www.getid3.org // // or http://getid3.sourceforge.net // // see readme.txt for more details // ///////////////////////////////////////////////////////////////// // // // module.audio.aac.php // // module for analyzing AAC Audio files // // dependencies: NONE // // /// ///////////////////////////////////////////////////////////////// if (!defined('GETID3_INCLUDEPATH')) { // prevent path-exposing attacks that access modules directly on public webservers exit; } class getid3_aac extends getid3_handler { /** * @return bool */ public function Analyze() { $info = &$this->getid3->info; $this->fseek($info['avdataoffset']); if ($this->fread(4) == 'ADIF') { $this->getAACADIFheaderFilepointer(); } else { $this->getAACADTSheaderFilepointer(); } return true; } /** * @return bool */ public function getAACADIFheaderFilepointer() { $info = &$this->getid3->info; $info['fileformat'] = 'aac'; $info['audio']['dataformat'] = 'aac'; $info['audio']['lossless'] = false; $this->fseek($info['avdataoffset']); $AACheader = $this->fread(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() // } // } $AACheaderBitstream = getid3_lib::BigEndian2Bin($AACheader); $bitoffset = 0; $info['aac']['header_type'] = 'ADIF'; $bitoffset += 32; $info['aac']['header']['mpeg_version'] = 4; $info['aac']['header']['copyright'] = substr($AACheaderBitstream, $bitoffset, 1) == '1'; $bitoffset += 1; if ($info['aac']['header']['copyright']) { $info['aac']['header']['copyright_id'] = getid3_lib::Bin2String(substr($AACheaderBitstream, $bitoffset, 72)); $bitoffset += 72; } $info['aac']['header']['original_copy'] = substr($AACheaderBitstream, $bitoffset, 1) == '1'; $bitoffset += 1; $info['aac']['header']['home'] = substr($AACheaderBitstream, $bitoffset, 1) == '1'; $bitoffset += 1; $info['aac']['header']['is_vbr'] = substr($AACheaderBitstream, $bitoffset, 1) == '1'; $bitoffset += 1; if ($info['aac']['header']['is_vbr']) { $info['audio']['bitrate_mode'] = 'vbr'; $info['aac']['header']['bitrate_max'] = getid3_lib::Bin2Dec(substr($AACheaderBitstream, $bitoffset, 23)); $bitoffset += 23; } else { $info['audio']['bitrate_mode'] = 'cbr'; $info['aac']['header']['bitrate'] = getid3_lib::Bin2Dec(substr($AACheaderBitstream, $bitoffset, 23)); $bitoffset += 23; $info['audio']['bitrate'] = $info['aac']['header']['bitrate']; } if ($info['audio']['bitrate'] == 0) { $this->error('Corrupt AAC file: bitrate_audio == zero'); return false; } $info['aac']['header']['num_program_configs'] = 1 + getid3_lib::Bin2Dec(substr($AACheaderBitstream, $bitoffset, 4)); $bitoffset += 4; for ($i = 0; $i < $info['aac']['header']['num_program_configs']; $i++) { // http://www.audiocoding.com/wiki/index.php?page=program_config_element // buffer_fullness 20 // element_instance_tag 4 // object_type 2 // sampling_frequency_index 4 // num_front_channel_elements 4 // num_side_channel_elements 4 // num_back_channel_elements 4 // num_lfe_channel_elements 2 // num_assoc_data_elements 3 // num_valid_cc_elements 4 // mono_mixdown_present 1 // mono_mixdown_element_number 4 if mono_mixdown_present == 1 // stereo_mixdown_present 1 // stereo_mixdown_element_number 4 if stereo_mixdown_present == 1 // matrix_mixdown_idx_present 1 // matrix_mixdown_idx 2 if matrix_mixdown_idx_present == 1 // pseudo_surround_enable 1 if matrix_mixdown_idx_present == 1 // for (i = 0; i < num_front_channel_elements; i++) { // front_element_is_cpe[i] 1 // front_element_tag_select[i] 4 // } // for (i = 0; i < num_side_channel_elements; i++) { // side_element_is_cpe[i] 1 // side_element_tag_select[i] 4 // } // for (i = 0; i < num_back_channel_elements; i++) { // back_element_is_cpe[i] 1 // back_element_tag_select[i] 4 // } // for (i = 0; i < num_lfe_channel_elements; i++) { // lfe_element_tag_select[i] 4 // } // for (i = 0; i < num_assoc_data_elements; i++) { // assoc_data_element_tag_select[i] 4 // } // for (i = 0; i < num_valid_cc_elements; i++) { // cc_element_is_ind_sw[i] 1 // valid_cc_element_tag_select[i] 4 // } // byte_alignment() VAR // comment_field_bytes 8 // for (i = 0; i < comment_field_bytes; i++) { // comment_field_data[i] 8 // } if (!$info['aac']['header']['is_vbr']) { $info['aac']['program_configs'][$i]['buffer_fullness'] = getid3_lib::Bin2Dec(substr($AACheaderBitstream, $bitoffset, 20)); $bitoffset += 20; } $info['aac']['program_configs'][$i]['element_instance_tag'] = getid3_lib::Bin2Dec(substr($AACheaderBitstream, $bitoffset, 4)); $bitoffset += 4; $info['aac']['program_configs'][$i]['object_type'] = getid3_lib::Bin2Dec(substr($AACheaderBitstream, $bitoffset, 2)); $bitoffset += 2; $info['aac']['program_configs'][$i]['sampling_frequency_index'] = getid3_lib::Bin2Dec(substr($AACheaderBitstream, $bitoffset, 4)); $bitoffset += 4; $info['aac']['program_configs'][$i]['num_front_channel_elements'] = getid3_lib::Bin2Dec(substr($AACheaderBitstream, $bitoffset, 4)); $bitoffset += 4; $info['aac']['program_configs'][$i]['num_side_channel_elements'] = getid3_lib::Bin2Dec(substr($AACheaderBitstream, $bitoffset, 4)); $bitoffset += 4; $info['aac']['program_configs'][$i]['num_back_channel_elements'] = getid3_lib::Bin2Dec(substr($AACheaderBitstream, $bitoffset, 4)); $bitoffset += 4; $info['aac']['program_configs'][$i]['num_lfe_channel_elements'] = getid3_lib::Bin2Dec(substr($AACheaderBitstream, $bitoffset, 2)); $bitoffset += 2; $info['aac']['program_configs'][$i]['num_assoc_data_elements'] = getid3_lib::Bin2Dec(substr($AACheaderBitstream, $bitoffset, 3)); $bitoffset += 3; $info['aac']['program_configs'][$i]['num_valid_cc_elements'] = getid3_lib::Bin2Dec(substr($AACheaderBitstream, $bitoffset, 4)); $bitoffset += 4; $info['aac']['program_configs'][$i]['mono_mixdown_present'] = (bool) getid3_lib::Bin2Dec(substr($AACheaderBitstream, $bitoffset, 1)); $bitoffset += 1; if ($info['aac']['program_configs'][$i]['mono_mixdown_present']) { $info['aac']['program_configs'][$i]['mono_mixdown_element_number'] = getid3_lib::Bin2Dec(substr($AACheaderBitstream, $bitoffset, 4)); $bitoffset += 4; } $info['aac']['program_configs'][$i]['stereo_mixdown_present'] = (bool) getid3_lib::Bin2Dec(substr($AACheaderBitstream, $bitoffset, 1)); $bitoffset += 1; if ($info['aac']['program_configs'][$i]['stereo_mixdown_present']) { $info['aac']['program_configs'][$i]['stereo_mixdown_element_number'] = getid3_lib::Bin2Dec(substr($AACheaderBitstream, $bitoffset, 4)); $bitoffset += 4; } $info['aac']['program_configs'][$i]['matrix_mixdown_idx_present'] = (bool) getid3_lib::Bin2Dec(substr($AACheaderBitstream, $bitoffset, 1)); $bitoffset += 1; if ($info['aac']['program_configs'][$i]['matrix_mixdown_idx_present']) { $info['aac']['program_configs'][$i]['matrix_mixdown_idx'] = getid3_lib::Bin2Dec(substr($AACheaderBitstream, $bitoffset, 2)); $bitoffset += 2; $info['aac']['program_configs'][$i]['pseudo_surround_enable'] = (bool) getid3_lib::Bin2Dec(substr($AACheaderBitstream, $bitoffset, 1)); $bitoffset += 1; } for ($j = 0; $j < $info['aac']['program_configs'][$i]['num_front_channel_elements']; $j++) { $info['aac']['program_configs'][$i]['front_element_is_cpe'][$j] = (bool) getid3_lib::Bin2Dec(substr($AACheaderBitstream, $bitoffset, 1)); $bitoffset += 1; $info['aac']['program_configs'][$i]['front_element_tag_select'][$j] = getid3_lib::Bin2Dec(substr($AACheaderBitstream, $bitoffset, 4)); $bitoffset += 4; } for ($j = 0; $j < $info['aac']['program_configs'][$i]['num_side_channel_elements']; $j++) { $info['aac']['program_configs'][$i]['side_element_is_cpe'][$j] = (bool) getid3_lib::Bin2Dec(substr($AACheaderBitstream, $bitoffset, 1)); $bitoffset += 1; $info['aac']['program_configs'][$i]['side_element_tag_select'][$j] = getid3_lib::Bin2Dec(substr($AACheaderBitstream, $bitoffset, 4)); $bitoffset += 4; } for ($j = 0; $j < $info['aac']['program_configs'][$i]['num_back_channel_elements']; $j++) { $info['aac']['program_configs'][$i]['back_element_is_cpe'][$j] = (bool) getid3_lib::Bin2Dec(substr($AACheaderBitstream, $bitoffset, 1)); $bitoffset += 1; $info['aac']['program_configs'][$i]['back_element_tag_select'][$j] = getid3_lib::Bin2Dec(substr($AACheaderBitstream, $bitoffset, 4)); $bitoffset += 4; } for ($j = 0; $j < $info['aac']['program_configs'][$i]['num_lfe_channel_elements']; $j++) { $info['aac']['program_configs'][$i]['lfe_element_tag_select'][$j] = getid3_lib::Bin2Dec(substr($AACheaderBitstream, $bitoffset, 4)); $bitoffset += 4; } for ($j = 0; $j < $info['aac']['program_configs'][$i]['num_assoc_data_elements']; $j++) { $info['aac']['program_configs'][$i]['assoc_data_element_tag_select'][$j] = getid3_lib::Bin2Dec(substr($AACheaderBitstream, $bitoffset, 4)); $bitoffset += 4; } for ($j = 0; $j < $info['aac']['program_configs'][$i]['num_valid_cc_elements']; $j++) { $info['aac']['program_configs'][$i]['cc_element_is_ind_sw'][$j] = (bool) getid3_lib::Bin2Dec(substr($AACheaderBitstream, $bitoffset, 1)); $bitoffset += 1; $info['aac']['program_configs'][$i]['valid_cc_element_tag_select'][$j] = getid3_lib::Bin2Dec(substr($AACheaderBitstream, $bitoffset, 4)); $bitoffset += 4; } $bitoffset = ceil($bitoffset / 8) * 8; $info['aac']['program_configs'][$i]['comment_field_bytes'] = getid3_lib::Bin2Dec(substr($AACheaderBitstream, $bitoffset, 8)); $bitoffset += 8; $info['aac']['program_configs'][$i]['comment_field'] = getid3_lib::Bin2String(substr($AACheaderBitstream, $bitoffset, 8 * $info['aac']['program_configs'][$i]['comment_field_bytes'])); $bitoffset += 8 * $info['aac']['program_configs'][$i]['comment_field_bytes']; $info['aac']['header']['profile'] = self::AACprofileLookup($info['aac']['program_configs'][$i]['object_type'], $info['aac']['header']['mpeg_version']); $info['aac']['program_configs'][$i]['sampling_frequency'] = self::AACsampleRateLookup($info['aac']['program_configs'][$i]['sampling_frequency_index']); $info['audio']['sample_rate'] = $info['aac']['program_configs'][$i]['sampling_frequency']; $info['audio']['channels'] = self::AACchannelCountCalculate($info['aac']['program_configs'][$i]); if ($info['aac']['program_configs'][$i]['comment_field']) { $info['aac']['comments'][] = $info['aac']['program_configs'][$i]['comment_field']; } } $info['playtime_seconds'] = (($info['avdataend'] - $info['avdataoffset']) * 8) / $info['audio']['bitrate']; $info['audio']['encoder_options'] = $info['aac']['header_type'].' '.$info['aac']['header']['profile']; return true; } else { unset($info['fileformat']); unset($info['aac']); $this->error('AAC-ADIF synch not found at offset '.$info['avdataoffset'].' (expected "ADIF", found "'.substr($AACheader, 0, 4).'" instead)'); return false; } } /** * @param int $MaxFramesToScan * @param bool $ReturnExtendedInfo * * @return bool */ public function getAACADTSheaderFilepointer($MaxFramesToScan=1000000, $ReturnExtendedInfo=false) { $info = &$this->getid3->info; // based loosely on code from AACfile by Jurgen Faul <jfaulØgmx.de> // http://jfaul.de/atl or http://j-faul.virtualave.net/atl/atl.html // http://faac.sourceforge.net/wiki/index.php?page=ADTS // dead link // http://wiki.multimedia.cx/index.php?title=ADTS // * ADTS Fixed Header: these don't change from frame to frame // syncword 12 always: '111111111111' // ID 1 0: MPEG-4, 1: MPEG-2 // MPEG layer 2 If you send AAC in MPEG-TS, set to 0 // protection_absent 1 0: CRC present; 1: no CRC // profile 2 0: AAC Main; 1: AAC LC (Low Complexity); 2: AAC SSR (Scalable Sample Rate); 3: AAC LTP (Long Term Prediction) // sampling_frequency_index 4 15 not allowed // private_bit 1 usually 0 // channel_configuration 3 // original/copy 1 0: original; 1: copy // home 1 usually 0 // emphasis 2 only if ID == 0 (ie MPEG-4) // not present in some documentation? // * 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 = $info['avdataoffset']; $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 $BitrateCache = array(); while (true) { // breaks out when end-of-file encountered, or invalid data found, // or MaxFramesToScan frames have been scanned if (!getid3_lib::intValueSupported($byteoffset)) { $this->warning('Unable to parse AAC file beyond '.$this->ftell().' (PHP does not support file operations beyond '.round(PHP_INT_MAX / 1073741824).'GB)'); return false; } $this->fseek($byteoffset); // First get substring $substring = $this->fread(9); // header is 7 bytes (or 9 if CRC is present) $substringlength = strlen($substring); if ($substringlength != 9) { $this->error('Failed to read 7 bytes at offset '.($this->ftell() - $substringlength).' (only read '.$substringlength.' bytes)'); return false; } // this would be easier with 64-bit math, but split it up to allow for 32-bit: $header1 = getid3_lib::BigEndian2Int(substr($substring, 0, 2)); $header2 = getid3_lib::BigEndian2Int(substr($substring, 2, 4)); $header3 = getid3_lib::BigEndian2Int(substr($substring, 6, 1)); $info['aac']['header']['raw']['syncword'] = ($header1 & 0xFFF0) >> 4; if ($info['aac']['header']['raw']['syncword'] != 0x0FFF) { $this->error('Synch pattern (0x0FFF) not found at offset '.($this->ftell() - $substringlength).' (found 0x0'.strtoupper(dechex($info['aac']['header']['raw']['syncword'])).' instead)'); //if ($info['fileformat'] == 'aac') { // return true; //} unset($info['aac']); return false; } // Gather info for first frame only - this takes time to do 1000 times! if ($framenumber == 0) { $info['aac']['header_type'] = 'ADTS'; $info['fileformat'] = 'aac'; $info['audio']['dataformat'] = 'aac'; $info['aac']['header']['raw']['mpeg_version'] = ($header1 & 0x0008) >> 3; $info['aac']['header']['raw']['mpeg_layer'] = ($header1 & 0x0006) >> 1; $info['aac']['header']['raw']['protection_absent'] = ($header1 & 0x0001) >> 0; $info['aac']['header']['raw']['profile_code'] = ($header2 & 0xC0000000) >> 30; $info['aac']['header']['raw']['sample_rate_code'] = ($header2 & 0x3C000000) >> 26; $info['aac']['header']['raw']['private_stream'] = ($header2 & 0x02000000) >> 25; $info['aac']['header']['raw']['channels_code'] = ($header2 & 0x01C00000) >> 22; $info['aac']['header']['raw']['original'] = ($header2 & 0x00200000) >> 21; $info['aac']['header']['raw']['home'] = ($header2 & 0x00100000) >> 20; $info['aac']['header']['raw']['copyright_stream'] = ($header2 & 0x00080000) >> 19; $info['aac']['header']['raw']['copyright_start'] = ($header2 & 0x00040000) >> 18; $info['aac']['header']['raw']['frame_length'] = ($header2 & 0x0003FFE0) >> 5; $info['aac']['header']['mpeg_version'] = ($info['aac']['header']['raw']['mpeg_version'] ? 2 : 4); $info['aac']['header']['crc_present'] = ($info['aac']['header']['raw']['protection_absent'] ? false: true); $info['aac']['header']['profile'] = self::AACprofileLookup($info['aac']['header']['raw']['profile_code'], $info['aac']['header']['mpeg_version']); $info['aac']['header']['sample_frequency'] = self::AACsampleRateLookup($info['aac']['header']['raw']['sample_rate_code']); $info['aac']['header']['private'] = (bool) $info['aac']['header']['raw']['private_stream']; $info['aac']['header']['original'] = (bool) $info['aac']['header']['raw']['original']; $info['aac']['header']['home'] = (bool) $info['aac']['header']['raw']['home']; $info['aac']['header']['channels'] = (($info['aac']['header']['raw']['channels_code'] == 7) ? 8 : $info['aac']['header']['raw']['channels_code']); if ($ReturnExtendedInfo) { $info['aac'][$framenumber]['copyright_id_bit'] = (bool) $info['aac']['header']['raw']['copyright_stream']; $info['aac'][$framenumber]['copyright_id_start'] = (bool) $info['aac']['header']['raw']['copyright_start']; } if ($info['aac']['header']['raw']['mpeg_layer'] != 0) { $this->warning('Layer error - expected "0", found "'.$info['aac']['header']['raw']['mpeg_layer'].'" instead'); } if ($info['aac']['header']['sample_frequency'] == 0) { $this->error('Corrupt AAC file: sample_frequency == zero'); return false; } $info['audio']['sample_rate'] = $info['aac']['header']['sample_frequency']; $info['audio']['channels'] = $info['aac']['header']['channels']; } $FrameLength = ($header2 & 0x0003FFE0) >> 5; if (!isset($BitrateCache[$FrameLength])) { $BitrateCache[$FrameLength] = ($info['aac']['header']['sample_frequency'] / 1024) * $FrameLength * 8; } getid3_lib::safe_inc($info['aac']['bitrate_distribution'][(string)$BitrateCache[$FrameLength]], 1); $info['aac'][$framenumber]['aac_frame_length'] = $FrameLength; $info['aac'][$framenumber]['adts_buffer_fullness'] = (($header2 & 0x0000001F) << 6) & (($header3 & 0xFC) >> 2); if ($info['aac'][$framenumber]['adts_buffer_fullness'] == 0x07FF) { $info['audio']['bitrate_mode'] = 'vbr'; } else { $info['audio']['bitrate_mode'] = 'cbr'; } $info['aac'][$framenumber]['num_raw_data_blocks'] = (($header3 & 0x03) >> 0); if ($info['aac']['header']['crc_present']) { //$info['aac'][$framenumber]['crc'] = getid3_lib::BigEndian2Int(substr($substring, 7, 2); } if (!$ReturnExtendedInfo) { unset($info['aac'][$framenumber]); } /* $rounded_precision = 5000; $info['aac']['bitrate_distribution_rounded'] = array(); foreach ($info['aac']['bitrate_distribution'] as $bitrate => $count) { $rounded_bitrate = round($bitrate / $rounded_precision) * $rounded_precision; getid3_lib::safe_inc($info['aac']['bitrate_distribution_rounded'][$rounded_bitrate], $count); } ksort($info['aac']['bitrate_distribution_rounded']); */ $byteoffset += $FrameLength; if ((++$framenumber < $MaxFramesToScan) && (($byteoffset + 10) < $info['avdataend'])) { // keep scanning } else { $info['aac']['frames'] = $framenumber; $info['playtime_seconds'] = ($info['avdataend'] / $byteoffset) * (($framenumber * 1024) / $info['aac']['header']['sample_frequency']); // (1 / % of file scanned) * (samples / (samples/sec)) = seconds if ($info['playtime_seconds'] == 0) { $this->error('Corrupt AAC file: playtime_seconds == zero'); return false; } $info['audio']['bitrate'] = (($info['avdataend'] - $info['avdataoffset']) * 8) / $info['playtime_seconds']; ksort($info['aac']['bitrate_distribution']); $info['audio']['encoder_options'] = $info['aac']['header_type'].' '.$info['aac']['header']['profile']; return true; } } // should never get here. } /** * @param int $samplerateid * * @return int|string */ public static function AACsampleRateLookup($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'); } /** * @param int $profileid * @param int $mpegversion * * @return string */ public static function AACprofileLookup($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'); } /** * @param array $program_configs * * @return int */ public static function AACchannelCountCalculate($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; } }