59d79def6944edb19b834fca9b78c4f87c5639b7
2 /////////////////////////////////////////////////////////////////
3 /// getID3() by James Heinrich <info@getid3.org> //
4 // available at http://getid3.sourceforge.net //
5 // or http://www.getid3.org //
6 // also https://github.com/JamesHeinrich/getID3 //
7 /////////////////////////////////////////////////////////////////
8 // See readme.txt for more details //
9 /////////////////////////////////////////////////////////////////
11 // module.audio.aac.php //
12 // module for analyzing AAC Audio files //
13 // dependencies: NONE //
15 /////////////////////////////////////////////////////////////////
18 class getid3_aac
extends getid3_handler
20 public function Analyze() {
21 $info = &$this->getid3
->info
;
22 $this->fseek($info['avdataoffset']);
23 if ($this->fread(4) == 'ADIF') {
24 $this->getAACADIFheaderFilepointer();
26 $this->getAACADTSheaderFilepointer();
33 public function getAACADIFheaderFilepointer() {
34 $info = &$this->getid3
->info
;
35 $info['fileformat'] = 'aac';
36 $info['audio']['dataformat'] = 'aac';
37 $info['audio']['lossless'] = false;
39 $this->fseek($info['avdataoffset']);
40 $AACheader = $this->fread(1024);
43 if (substr($AACheader, 0, 4) == 'ADIF') {
45 // http://faac.sourceforge.net/wiki/index.php?page=ADIF
47 // http://libmpeg.org/mpeg4/doc/w2203tfs.pdf
50 // copyright_id_present 1
51 // if( copyright_id_present )
57 // num_program_config_elements 4
58 // for (i = 0; i < num_program_config_elements + 1; i++ ) {
59 // if( bitstream_type == '0' )
60 // adif_buffer_fullness 20
61 // program_config_element()
65 $AACheaderBitstream = getid3_lib
::BigEndian2Bin($AACheader);
68 $info['aac']['header_type'] = 'ADIF';
70 $info['aac']['header']['mpeg_version'] = 4;
72 $info['aac']['header']['copyright'] = (bool) (substr($AACheaderBitstream, $bitoffset, 1) == '1');
74 if ($info['aac']['header']['copyright']) {
75 $info['aac']['header']['copyright_id'] = getid3_lib
::Bin2String(substr($AACheaderBitstream, $bitoffset, 72));
78 $info['aac']['header']['original_copy'] = (bool) (substr($AACheaderBitstream, $bitoffset, 1) == '1');
80 $info['aac']['header']['home'] = (bool) (substr($AACheaderBitstream, $bitoffset, 1) == '1');
82 $info['aac']['header']['is_vbr'] = (bool) (substr($AACheaderBitstream, $bitoffset, 1) == '1');
84 if ($info['aac']['header']['is_vbr']) {
85 $info['audio']['bitrate_mode'] = 'vbr';
86 $info['aac']['header']['bitrate_max'] = getid3_lib
::Bin2Dec(substr($AACheaderBitstream, $bitoffset, 23));
89 $info['audio']['bitrate_mode'] = 'cbr';
90 $info['aac']['header']['bitrate'] = getid3_lib
::Bin2Dec(substr($AACheaderBitstream, $bitoffset, 23));
92 $info['audio']['bitrate'] = $info['aac']['header']['bitrate'];
94 if ($info['audio']['bitrate'] == 0) {
95 $this->error('Corrupt AAC file: bitrate_audio == zero');
98 $info['aac']['header']['num_program_configs'] = 1 + getid3_lib
::Bin2Dec(substr($AACheaderBitstream, $bitoffset, 4));
101 for ($i = 0; $i < $info['aac']['header']['num_program_configs']; $i++
) {
102 // http://www.audiocoding.com/wiki/index.php?page=program_config_element
104 // buffer_fullness 20
106 // element_instance_tag 4
108 // sampling_frequency_index 4
109 // num_front_channel_elements 4
110 // num_side_channel_elements 4
111 // num_back_channel_elements 4
112 // num_lfe_channel_elements 2
113 // num_assoc_data_elements 3
114 // num_valid_cc_elements 4
115 // mono_mixdown_present 1
116 // mono_mixdown_element_number 4 if mono_mixdown_present == 1
117 // stereo_mixdown_present 1
118 // stereo_mixdown_element_number 4 if stereo_mixdown_present == 1
119 // matrix_mixdown_idx_present 1
120 // matrix_mixdown_idx 2 if matrix_mixdown_idx_present == 1
121 // pseudo_surround_enable 1 if matrix_mixdown_idx_present == 1
122 // for (i = 0; i < num_front_channel_elements; i++) {
123 // front_element_is_cpe[i] 1
124 // front_element_tag_select[i] 4
126 // for (i = 0; i < num_side_channel_elements; i++) {
127 // side_element_is_cpe[i] 1
128 // side_element_tag_select[i] 4
130 // for (i = 0; i < num_back_channel_elements; i++) {
131 // back_element_is_cpe[i] 1
132 // back_element_tag_select[i] 4
134 // for (i = 0; i < num_lfe_channel_elements; i++) {
135 // lfe_element_tag_select[i] 4
137 // for (i = 0; i < num_assoc_data_elements; i++) {
138 // assoc_data_element_tag_select[i] 4
140 // for (i = 0; i < num_valid_cc_elements; i++) {
141 // cc_element_is_ind_sw[i] 1
142 // valid_cc_element_tag_select[i] 4
144 // byte_alignment() VAR
145 // comment_field_bytes 8
146 // for (i = 0; i < comment_field_bytes; i++) {
147 // comment_field_data[i] 8
150 if (!$info['aac']['header']['is_vbr']) {
151 $info['aac']['program_configs'][$i]['buffer_fullness'] = getid3_lib
::Bin2Dec(substr($AACheaderBitstream, $bitoffset, 20));
154 $info['aac']['program_configs'][$i]['element_instance_tag'] = getid3_lib
::Bin2Dec(substr($AACheaderBitstream, $bitoffset, 4));
156 $info['aac']['program_configs'][$i]['object_type'] = getid3_lib
::Bin2Dec(substr($AACheaderBitstream, $bitoffset, 2));
158 $info['aac']['program_configs'][$i]['sampling_frequency_index'] = getid3_lib
::Bin2Dec(substr($AACheaderBitstream, $bitoffset, 4));
160 $info['aac']['program_configs'][$i]['num_front_channel_elements'] = getid3_lib
::Bin2Dec(substr($AACheaderBitstream, $bitoffset, 4));
162 $info['aac']['program_configs'][$i]['num_side_channel_elements'] = getid3_lib
::Bin2Dec(substr($AACheaderBitstream, $bitoffset, 4));
164 $info['aac']['program_configs'][$i]['num_back_channel_elements'] = getid3_lib
::Bin2Dec(substr($AACheaderBitstream, $bitoffset, 4));
166 $info['aac']['program_configs'][$i]['num_lfe_channel_elements'] = getid3_lib
::Bin2Dec(substr($AACheaderBitstream, $bitoffset, 2));
168 $info['aac']['program_configs'][$i]['num_assoc_data_elements'] = getid3_lib
::Bin2Dec(substr($AACheaderBitstream, $bitoffset, 3));
170 $info['aac']['program_configs'][$i]['num_valid_cc_elements'] = getid3_lib
::Bin2Dec(substr($AACheaderBitstream, $bitoffset, 4));
172 $info['aac']['program_configs'][$i]['mono_mixdown_present'] = (bool) getid3_lib
::Bin2Dec(substr($AACheaderBitstream, $bitoffset, 1));
174 if ($info['aac']['program_configs'][$i]['mono_mixdown_present']) {
175 $info['aac']['program_configs'][$i]['mono_mixdown_element_number'] = getid3_lib
::Bin2Dec(substr($AACheaderBitstream, $bitoffset, 4));
178 $info['aac']['program_configs'][$i]['stereo_mixdown_present'] = (bool) getid3_lib
::Bin2Dec(substr($AACheaderBitstream, $bitoffset, 1));
180 if ($info['aac']['program_configs'][$i]['stereo_mixdown_present']) {
181 $info['aac']['program_configs'][$i]['stereo_mixdown_element_number'] = getid3_lib
::Bin2Dec(substr($AACheaderBitstream, $bitoffset, 4));
184 $info['aac']['program_configs'][$i]['matrix_mixdown_idx_present'] = (bool) getid3_lib
::Bin2Dec(substr($AACheaderBitstream, $bitoffset, 1));
186 if ($info['aac']['program_configs'][$i]['matrix_mixdown_idx_present']) {
187 $info['aac']['program_configs'][$i]['matrix_mixdown_idx'] = getid3_lib
::Bin2Dec(substr($AACheaderBitstream, $bitoffset, 2));
189 $info['aac']['program_configs'][$i]['pseudo_surround_enable'] = (bool) getid3_lib
::Bin2Dec(substr($AACheaderBitstream, $bitoffset, 1));
192 for ($j = 0; $j < $info['aac']['program_configs'][$i]['num_front_channel_elements']; $j++
) {
193 $info['aac']['program_configs'][$i]['front_element_is_cpe'][$j] = (bool) getid3_lib
::Bin2Dec(substr($AACheaderBitstream, $bitoffset, 1));
195 $info['aac']['program_configs'][$i]['front_element_tag_select'][$j] = getid3_lib
::Bin2Dec(substr($AACheaderBitstream, $bitoffset, 4));
198 for ($j = 0; $j < $info['aac']['program_configs'][$i]['num_side_channel_elements']; $j++
) {
199 $info['aac']['program_configs'][$i]['side_element_is_cpe'][$j] = (bool) getid3_lib
::Bin2Dec(substr($AACheaderBitstream, $bitoffset, 1));
201 $info['aac']['program_configs'][$i]['side_element_tag_select'][$j] = getid3_lib
::Bin2Dec(substr($AACheaderBitstream, $bitoffset, 4));
204 for ($j = 0; $j < $info['aac']['program_configs'][$i]['num_back_channel_elements']; $j++
) {
205 $info['aac']['program_configs'][$i]['back_element_is_cpe'][$j] = (bool) getid3_lib
::Bin2Dec(substr($AACheaderBitstream, $bitoffset, 1));
207 $info['aac']['program_configs'][$i]['back_element_tag_select'][$j] = getid3_lib
::Bin2Dec(substr($AACheaderBitstream, $bitoffset, 4));
210 for ($j = 0; $j < $info['aac']['program_configs'][$i]['num_lfe_channel_elements']; $j++
) {
211 $info['aac']['program_configs'][$i]['lfe_element_tag_select'][$j] = getid3_lib
::Bin2Dec(substr($AACheaderBitstream, $bitoffset, 4));
214 for ($j = 0; $j < $info['aac']['program_configs'][$i]['num_assoc_data_elements']; $j++
) {
215 $info['aac']['program_configs'][$i]['assoc_data_element_tag_select'][$j] = getid3_lib
::Bin2Dec(substr($AACheaderBitstream, $bitoffset, 4));
218 for ($j = 0; $j < $info['aac']['program_configs'][$i]['num_valid_cc_elements']; $j++
) {
219 $info['aac']['program_configs'][$i]['cc_element_is_ind_sw'][$j] = (bool) getid3_lib
::Bin2Dec(substr($AACheaderBitstream, $bitoffset, 1));
221 $info['aac']['program_configs'][$i]['valid_cc_element_tag_select'][$j] = getid3_lib
::Bin2Dec(substr($AACheaderBitstream, $bitoffset, 4));
225 $bitoffset = ceil($bitoffset / 8) * 8;
227 $info['aac']['program_configs'][$i]['comment_field_bytes'] = getid3_lib
::Bin2Dec(substr($AACheaderBitstream, $bitoffset, 8));
229 $info['aac']['program_configs'][$i]['comment_field'] = getid3_lib
::Bin2String(substr($AACheaderBitstream, $bitoffset, 8 * $info['aac']['program_configs'][$i]['comment_field_bytes']));
230 $bitoffset +
= 8 * $info['aac']['program_configs'][$i]['comment_field_bytes'];
233 $info['aac']['header']['profile'] = self
::AACprofileLookup($info['aac']['program_configs'][$i]['object_type'], $info['aac']['header']['mpeg_version']);
234 $info['aac']['program_configs'][$i]['sampling_frequency'] = self
::AACsampleRateLookup($info['aac']['program_configs'][$i]['sampling_frequency_index']);
235 $info['audio']['sample_rate'] = $info['aac']['program_configs'][$i]['sampling_frequency'];
236 $info['audio']['channels'] = self
::AACchannelCountCalculate($info['aac']['program_configs'][$i]);
237 if ($info['aac']['program_configs'][$i]['comment_field']) {
238 $info['aac']['comments'][] = $info['aac']['program_configs'][$i]['comment_field'];
241 $info['playtime_seconds'] = (($info['avdataend'] - $info['avdataoffset']) * 8) / $info['audio']['bitrate'];
243 $info['audio']['encoder_options'] = $info['aac']['header_type'].' '.$info['aac']['header']['profile'];
251 unset($info['fileformat']);
253 $this->error('AAC-ADIF synch not found at offset '.$info['avdataoffset'].' (expected "ADIF", found "'.substr($AACheader, 0, 4).'" instead)');
261 public function getAACADTSheaderFilepointer($MaxFramesToScan=1000000, $ReturnExtendedInfo=false) {
262 $info = &$this->getid3
->info
;
264 // based loosely on code from AACfile by Jurgen Faul <jfaulØgmx.de>
265 // http://jfaul.de/atl or http://j-faul.virtualave.net/atl/atl.html
268 // http://faac.sourceforge.net/wiki/index.php?page=ADTS // dead link
269 // http://wiki.multimedia.cx/index.php?title=ADTS
271 // * ADTS Fixed Header: these don't change from frame to frame
272 // syncword 12 always: '111111111111'
273 // ID 1 0: MPEG-4, 1: MPEG-2
274 // MPEG layer 2 If you send AAC in MPEG-TS, set to 0
275 // protection_absent 1 0: CRC present; 1: no CRC
276 // profile 2 0: AAC Main; 1: AAC LC (Low Complexity); 2: AAC SSR (Scalable Sample Rate); 3: AAC LTP (Long Term Prediction)
277 // sampling_frequency_index 4 15 not allowed
278 // private_bit 1 usually 0
279 // channel_configuration 3
280 // original/copy 1 0: original; 1: copy
282 // emphasis 2 only if ID == 0 (ie MPEG-4) // not present in some documentation?
284 // * ADTS Variable Header: these can change from frame to frame
285 // copyright_identification_bit 1
286 // copyright_identification_start 1
287 // aac_frame_length 13 length of the frame including header (in bytes)
288 // adts_buffer_fullness 11 0x7FF indicates VBR
289 // no_raw_data_blocks_in_frame 2
291 // * ADTS Error check
292 // crc_check 16 only if protection_absent == 0
294 $byteoffset = $info['avdataoffset'];
297 // Init bit pattern array
298 static $decbin = array();
301 for ($i = 0; $i < 256; $i++
) {
302 $decbin[chr($i)] = str_pad(decbin($i), 8, '0', STR_PAD_LEFT
);
305 // used to calculate bitrate below
306 $BitrateCache = array();
310 // breaks out when end-of-file encountered, or invalid data found,
311 // or MaxFramesToScan frames have been scanned
313 if (!getid3_lib
::intValueSupported($byteoffset)) {
314 $this->warning('Unable to parse AAC file beyond '.$this->ftell().' (PHP does not support file operations beyond '.round(PHP_INT_MAX
/ 1073741824).'GB)');
317 $this->fseek($byteoffset);
319 // First get substring
320 $substring = $this->fread(9); // header is 7 bytes (or 9 if CRC is present)
321 $substringlength = strlen($substring);
322 if ($substringlength != 9) {
323 $this->error('Failed to read 7 bytes at offset '.($this->ftell() - $substringlength).' (only read '.$substringlength.' bytes)');
326 // this would be easier with 64-bit math, but split it up to allow for 32-bit:
327 $header1 = getid3_lib
::BigEndian2Int(substr($substring, 0, 2));
328 $header2 = getid3_lib
::BigEndian2Int(substr($substring, 2, 4));
329 $header3 = getid3_lib
::BigEndian2Int(substr($substring, 6, 1));
331 $info['aac']['header']['raw']['syncword'] = ($header1 & 0xFFF0) >> 4;
332 if ($info['aac']['header']['raw']['syncword'] != 0x0FFF) {
333 $this->error('Synch pattern (0x0FFF) not found at offset '.($this->ftell() - $substringlength).' (found 0x0'.strtoupper(dechex($info['aac']['header']['raw']['syncword'])).' instead)');
334 //if ($info['fileformat'] == 'aac') {
341 // Gather info for first frame only - this takes time to do 1000 times!
342 if ($framenumber == 0) {
343 $info['aac']['header_type'] = 'ADTS';
344 $info['fileformat'] = 'aac';
345 $info['audio']['dataformat'] = 'aac';
347 $info['aac']['header']['raw']['mpeg_version'] = ($header1 & 0x0008) >> 3;
348 $info['aac']['header']['raw']['mpeg_layer'] = ($header1 & 0x0006) >> 1;
349 $info['aac']['header']['raw']['protection_absent'] = ($header1 & 0x0001) >> 0;
351 $info['aac']['header']['raw']['profile_code'] = ($header2 & 0xC0000000) >> 30;
352 $info['aac']['header']['raw']['sample_rate_code'] = ($header2 & 0x3C000000) >> 26;
353 $info['aac']['header']['raw']['private_stream'] = ($header2 & 0x02000000) >> 25;
354 $info['aac']['header']['raw']['channels_code'] = ($header2 & 0x01C00000) >> 22;
355 $info['aac']['header']['raw']['original'] = ($header2 & 0x00200000) >> 21;
356 $info['aac']['header']['raw']['home'] = ($header2 & 0x00100000) >> 20;
357 $info['aac']['header']['raw']['copyright_stream'] = ($header2 & 0x00080000) >> 19;
358 $info['aac']['header']['raw']['copyright_start'] = ($header2 & 0x00040000) >> 18;
359 $info['aac']['header']['raw']['frame_length'] = ($header2 & 0x0003FFE0) >> 5;
361 $info['aac']['header']['mpeg_version'] = ($info['aac']['header']['raw']['mpeg_version'] ?
2 : 4);
362 $info['aac']['header']['crc_present'] = ($info['aac']['header']['raw']['protection_absent'] ?
false: true);
363 $info['aac']['header']['profile'] = self
::AACprofileLookup($info['aac']['header']['raw']['profile_code'], $info['aac']['header']['mpeg_version']);
364 $info['aac']['header']['sample_frequency'] = self
::AACsampleRateLookup($info['aac']['header']['raw']['sample_rate_code']);
365 $info['aac']['header']['private'] = (bool) $info['aac']['header']['raw']['private_stream'];
366 $info['aac']['header']['original'] = (bool) $info['aac']['header']['raw']['original'];
367 $info['aac']['header']['home'] = (bool) $info['aac']['header']['raw']['home'];
368 $info['aac']['header']['channels'] = (($info['aac']['header']['raw']['channels_code'] == 7) ?
8 : $info['aac']['header']['raw']['channels_code']);
369 if ($ReturnExtendedInfo) {
370 $info['aac'][$framenumber]['copyright_id_bit'] = (bool) $info['aac']['header']['raw']['copyright_stream'];
371 $info['aac'][$framenumber]['copyright_id_start'] = (bool) $info['aac']['header']['raw']['copyright_start'];
374 if ($info['aac']['header']['raw']['mpeg_layer'] != 0) {
375 $this->warning('Layer error - expected "0", found "'.$info['aac']['header']['raw']['mpeg_layer'].'" instead');
377 if ($info['aac']['header']['sample_frequency'] == 0) {
378 $this->error('Corrupt AAC file: sample_frequency == zero');
382 $info['audio']['sample_rate'] = $info['aac']['header']['sample_frequency'];
383 $info['audio']['channels'] = $info['aac']['header']['channels'];
386 $FrameLength = ($header2 & 0x0003FFE0) >> 5;
388 if (!isset($BitrateCache[$FrameLength])) {
389 $BitrateCache[$FrameLength] = ($info['aac']['header']['sample_frequency'] / 1024) * $FrameLength * 8;
391 getid3_lib
::safe_inc($info['aac']['bitrate_distribution'][$BitrateCache[$FrameLength]], 1);
393 $info['aac'][$framenumber]['aac_frame_length'] = $FrameLength;
395 $info['aac'][$framenumber]['adts_buffer_fullness'] = (($header2 & 0x0000001F) << 6) & (($header3 & 0xFC) >> 2);
396 if ($info['aac'][$framenumber]['adts_buffer_fullness'] == 0x07FF) {
397 $info['audio']['bitrate_mode'] = 'vbr';
399 $info['audio']['bitrate_mode'] = 'cbr';
401 $info['aac'][$framenumber]['num_raw_data_blocks'] = (($header3 & 0x03) >> 0);
403 if ($info['aac']['header']['crc_present']) {
404 //$info['aac'][$framenumber]['crc'] = getid3_lib::BigEndian2Int(substr($substring, 7, 2);
407 if (!$ReturnExtendedInfo) {
408 unset($info['aac'][$framenumber]);
412 $rounded_precision = 5000;
413 $info['aac']['bitrate_distribution_rounded'] = array();
414 foreach ($info['aac']['bitrate_distribution'] as $bitrate => $count) {
415 $rounded_bitrate = round($bitrate / $rounded_precision) * $rounded_precision;
416 getid3_lib::safe_inc($info['aac']['bitrate_distribution_rounded'][$rounded_bitrate], $count);
418 ksort($info['aac']['bitrate_distribution_rounded']);
421 $byteoffset +
= $FrameLength;
422 if ((++
$framenumber < $MaxFramesToScan) && (($byteoffset +
10) < $info['avdataend'])) {
428 $info['aac']['frames'] = $framenumber;
429 $info['playtime_seconds'] = ($info['avdataend'] / $byteoffset) * (($framenumber * 1024) / $info['aac']['header']['sample_frequency']); // (1 / % of file scanned) * (samples / (samples/sec)) = seconds
430 if ($info['playtime_seconds'] == 0) {
431 $this->error('Corrupt AAC file: playtime_seconds == zero');
434 $info['audio']['bitrate'] = (($info['avdataend'] - $info['avdataoffset']) * 8) / $info['playtime_seconds'];
435 ksort($info['aac']['bitrate_distribution']);
437 $info['audio']['encoder_options'] = $info['aac']['header_type'].' '.$info['aac']['header']['profile'];
443 // should never get here.
446 public static function AACsampleRateLookup($samplerateid) {
447 static $AACsampleRateLookup = array();
448 if (empty($AACsampleRateLookup)) {
449 $AACsampleRateLookup[0] = 96000;
450 $AACsampleRateLookup[1] = 88200;
451 $AACsampleRateLookup[2] = 64000;
452 $AACsampleRateLookup[3] = 48000;
453 $AACsampleRateLookup[4] = 44100;
454 $AACsampleRateLookup[5] = 32000;
455 $AACsampleRateLookup[6] = 24000;
456 $AACsampleRateLookup[7] = 22050;
457 $AACsampleRateLookup[8] = 16000;
458 $AACsampleRateLookup[9] = 12000;
459 $AACsampleRateLookup[10] = 11025;
460 $AACsampleRateLookup[11] = 8000;
461 $AACsampleRateLookup[12] = 0;
462 $AACsampleRateLookup[13] = 0;
463 $AACsampleRateLookup[14] = 0;
464 $AACsampleRateLookup[15] = 0;
466 return (isset($AACsampleRateLookup[$samplerateid]) ?
$AACsampleRateLookup[$samplerateid] : 'invalid');
469 public static function AACprofileLookup($profileid, $mpegversion) {
470 static $AACprofileLookup = array();
471 if (empty($AACprofileLookup)) {
472 $AACprofileLookup[2][0] = 'Main profile';
473 $AACprofileLookup[2][1] = 'Low Complexity profile (LC)';
474 $AACprofileLookup[2][2] = 'Scalable Sample Rate profile (SSR)';
475 $AACprofileLookup[2][3] = '(reserved)';
476 $AACprofileLookup[4][0] = 'AAC_MAIN';
477 $AACprofileLookup[4][1] = 'AAC_LC';
478 $AACprofileLookup[4][2] = 'AAC_SSR';
479 $AACprofileLookup[4][3] = 'AAC_LTP';
481 return (isset($AACprofileLookup[$mpegversion][$profileid]) ?
$AACprofileLookup[$mpegversion][$profileid] : 'invalid');
484 public static function AACchannelCountCalculate($program_configs) {
486 for ($i = 0; $i < $program_configs['num_front_channel_elements']; $i++
) {
488 if ($program_configs['front_element_is_cpe'][$i]) {
489 // each front element is channel pair (CPE = Channel Pair Element)
493 for ($i = 0; $i < $program_configs['num_side_channel_elements']; $i++
) {
495 if ($program_configs['side_element_is_cpe'][$i]) {
496 // each side element is channel pair (CPE = Channel Pair Element)
500 for ($i = 0; $i < $program_configs['num_back_channel_elements']; $i++
) {
502 if ($program_configs['back_element_is_cpe'][$i]) {
503 // each back element is channel pair (CPE = Channel Pair Element)
507 for ($i = 0; $i < $program_configs['num_lfe_channel_elements']; $i++
) {