Context Navigation

source: extensions/charlies_content/getid3/getid3/module.audio.ac3.php @ 3318

Last change on this file since 3318 was 3318, checked in by vdigital, 15 years ago
+ Add Charlies' content to depository
Property svn:eol-style set to `LF` Property svn:keywords set to `Author Date Id Revision`
File size: 21.1 KB

Line
1	<?php
2	// +----------------------------------------------------------------------+
3	// \| PHP version 5 \|
4	// +----------------------------------------------------------------------+
5	// \| Copyright (c) 2002-2006 James Heinrich, Allan Hansen \|
6	// +----------------------------------------------------------------------+
7	// \| This source file is subject to version 2 of the GPL license, \|
8	// \| that is bundled with this package in the file license.txt and is \|
9	// \| available through the world-wide-web at the following url: \|
10	// \| http://www.gnu.org/copyleft/gpl.html \|
11	// +----------------------------------------------------------------------+
12	// \| getID3() - http://getid3.sourceforge.net or http://www.getid3.org \|
13	// +----------------------------------------------------------------------+
14	// \| Authors: James Heinrich <infoØgetid3*org> \|
15	// \| Allan Hansen <ahØartemis*dk> \|
16	// +----------------------------------------------------------------------+
17	// \| module.audio.ac3.php \|
18	// \| Module for analyzing AC-3 (aka Dolby Digital) audio files \|
19	// \| dependencies: NONE \|
20	// +----------------------------------------------------------------------+
21	//
22	// $Id: module.audio.ac3.php 3318 2009-05-20 21:54:10Z vdigital $
23
24
25
26	class getid3_ac3 extends getid3_handler
27	{
28
29	public function Analyze() {
30
31	$getid3 = $this->getid3;
32
33	// http://www.atsc.org/standards/a_52a.pdf
34
35	$getid3->info['fileformat'] = 'ac3';
36	$getid3->info['audio']['dataformat'] = 'ac3';
37	$getid3->info['audio']['bitrate_mode'] = 'cbr';
38	$getid3->info['audio']['lossless'] = false;
39
40	$getid3->info['ac3']['raw']['bsi'] = array ();
41	$info_ac3 = &$getid3->info['ac3'];
42	$info_ac3_raw = &$info_ac3['raw'];
43	$info_ac3_raw_bsi = &$info_ac3_raw['bsi'];
44
45
46	// An AC-3 serial coded audio bit stream is made up of a sequence of synchronization frames
47	// Each synchronization frame contains 6 coded audio blocks (AB), each of which represent 256
48	// new audio samples per channel. A synchronization information (SI) header at the beginning
49	// of each frame contains information needed to acquire and maintain synchronization. A
50	// bit stream information (BSI) header follows SI, and contains parameters describing the coded
51	// audio service. The coded audio blocks may be followed by an auxiliary data (Aux) field. At the
52	// end of each frame is an error check field that includes a CRC word for error detection. An
53	// additional CRC word is located in the SI header, the use of which, by a decoder, is optional.
54	//
55	// syncinfo() \| bsi() \| AB0 \| AB1 \| AB2 \| AB3 \| AB4 \| AB5 \| Aux \| CRC
56
57	$this->fseek($getid3->info['avdataoffset'], SEEK_SET);
58	$ac3_header['syncinfo'] = $this->fread(5);
59	$info_ac3_raw['synchinfo']['synchword'] = substr($ac3_header['syncinfo'], 0, 2);
60
61	if ($info_ac3_raw['synchinfo']['synchword'] != "\x0B\x77") {
62	throw new getid3_exception('Expecting "\x0B\x77" at offset '.$getid3->info['avdataoffset'].', found \x'.strtoupper(dechex($ac3_header['syncinfo']{0})).'\x'.strtoupper(dechex($ac3_header['syncinfo']{1})).' instead');
63	}
64
65
66	// syncinfo() {
67	// syncword 16
68	// crc1 16
69	// fscod 2
70	// frmsizecod 6
71	// } /* end of syncinfo */
72
73	$info_ac3_raw['synchinfo']['crc1'] = getid3_lib::LittleEndian2Int(substr($ac3_header['syncinfo'], 2, 2));
74	$ac3_synchinfo_fscod_frmsizecod = getid3_lib::LittleEndian2Int(substr($ac3_header['syncinfo'], 4, 1));
75	$info_ac3_raw['synchinfo']['fscod'] = ($ac3_synchinfo_fscod_frmsizecod & 0xC0) >> 6;
76	$info_ac3_raw['synchinfo']['frmsizecod'] = ($ac3_synchinfo_fscod_frmsizecod & 0x3F);
77
78	$info_ac3['sample_rate'] = getid3_ac3::AC3sampleRateCodeLookup($info_ac3_raw['synchinfo']['fscod']);
79	if ($info_ac3_raw['synchinfo']['fscod'] <= 3) {
80	$getid3->info['audio']['sample_rate'] = $info_ac3['sample_rate'];
81	}
82
83	$info_ac3['frame_length'] = getid3_ac3::AC3frameSizeLookup($info_ac3_raw['synchinfo']['frmsizecod'], $info_ac3_raw['synchinfo']['fscod']);
84	$info_ac3['bitrate'] = getid3_ac3::AC3bitrateLookup($info_ac3_raw['synchinfo']['frmsizecod']);
85	$getid3->info['audio']['bitrate'] = $info_ac3['bitrate'];
86
87	$ac3_header['bsi'] = getid3_lib::BigEndian2Bin($this->fread(15));
88
89	$info_ac3_raw_bsi['bsid'] = bindec(substr($ac3_header['bsi'], 0, 5));
90	if ($info_ac3_raw_bsi['bsid'] > 8) {
91	// Decoders which can decode version 8 will thus be able to decode version numbers less than 8.
92	// If this standard is extended by the addition of additional elements or features, a value of bsid greater than 8 will be used.
93	// Decoders built to this version of the standard will not be able to decode versions with bsid greater than 8.
94	throw new getid3_exception('Bit stream identification is version '.$info_ac3_raw_bsi['bsid'].', but getID3() only understands up to version 8');
95	}
96
97	$info_ac3_raw_bsi['bsmod'] = bindec(substr($ac3_header['bsi'], 5, 3));
98	$info_ac3_raw_bsi['acmod'] = bindec(substr($ac3_header['bsi'], 8, 3));
99
100	$info_ac3['service_type'] = getid3_ac3::AC3serviceTypeLookup($info_ac3_raw_bsi['bsmod'], $info_ac3_raw_bsi['acmod']);
101	$ac3_coding_mode = getid3_ac3::AC3audioCodingModeLookup($info_ac3_raw_bsi['acmod']);
102	foreach($ac3_coding_mode as $key => $value) {
103	$info_ac3[$key] = $value;
104	}
105	switch ($info_ac3_raw_bsi['acmod']) {
106	case 0:
107	case 1:
108	$getid3->info['audio']['channelmode'] = 'mono';
109	break;
110	case 3:
111	case 4:
112	$getid3->info['audio']['channelmode'] = 'stereo';
113	break;
114	default:
115	$getid3->info['audio']['channelmode'] = 'surround';
116	break;
117	}
118	$getid3->info['audio']['channels'] = $info_ac3['num_channels'];
119
120	$offset = 11;
121
122	if ($info_ac3_raw_bsi['acmod'] & 0x01) {
123	// If the lsb of acmod is a 1, center channel is in use and cmixlev follows in the bit stream.
124	$info_ac3_raw_bsi['cmixlev'] = bindec(substr($ac3_header['bsi'], $offset, 2));
125	$info_ac3['center_mix_level'] = getid3_ac3::AC3centerMixLevelLookup($info_ac3_raw_bsi['cmixlev']);
126	$offset += 2;
127	}
128
129	if ($info_ac3_raw_bsi['acmod'] & 0x04) {
130	// If the msb of acmod is a 1, surround channels are in use and surmixlev follows in the bit stream.
131	$info_ac3_raw_bsi['surmixlev'] = bindec(substr($ac3_header['bsi'], $offset, 2));
132	$info_ac3['surround_mix_level'] = getid3_ac3::AC3surroundMixLevelLookup($info_ac3_raw_bsi['surmixlev']);
133	$offset += 2;
134	}
135
136	if ($info_ac3_raw_bsi['acmod'] == 0x02) {
137	// When operating in the two channel mode, this 2-bit code indicates whether or not the program has been encoded in Dolby Surround.
138	$info_ac3_raw_bsi['dsurmod'] = bindec(substr($ac3_header['bsi'], $offset, 2));
139	$info_ac3['dolby_surround_mode'] = getid3_ac3::AC3dolbySurroundModeLookup($info_ac3_raw_bsi['dsurmod']);
140	$offset += 2;
141	}
142
143	$info_ac3_raw_bsi['lfeon'] = $ac3_header['bsi']{$offset++} == '1';
144	$info_ac3['lfe_enabled'] = $info_ac3_raw_bsi['lfeon'];
145	if ($info_ac3_raw_bsi['lfeon']) {
146	$getid3->info['audio']['channels'] .= '.1';
147	}
148
149	$info_ac3['channels_enabled'] = getid3_ac3::AC3channelsEnabledLookup($info_ac3_raw_bsi['acmod'], $info_ac3_raw_bsi['lfeon']);
150
151	// This indicates how far the average dialogue level is below digital 100 percent. Valid values are 131.
152	// 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.
153	$info_ac3_raw_bsi['dialnorm'] = bindec(substr($ac3_header['bsi'], $offset, 5));
154	$offset += 5;
155	$info_ac3['dialogue_normalization'] = '-'.$info_ac3_raw_bsi['dialnorm'].'dB';
156
157	$info_ac3_raw_bsi['compre_flag'] = $ac3_header['bsi']{$offset++} == '1';
158	if ($info_ac3_raw_bsi['compre_flag']) {
159	$info_ac3_raw_bsi['compr'] = bindec(substr($ac3_header['bsi'], $offset, 8));
160	$offset += 8;
161
162	$info_ac3['heavy_compression'] = getid3_ac3::AC3heavyCompression($info_ac3_raw_bsi['compr']);
163	}
164
165	$info_ac3_raw_bsi['langcode_flag'] = $ac3_header['bsi']{$offset++} == '1';
166	if ($info_ac3_raw_bsi['langcode_flag']) {
167	$info_ac3_raw_bsi['langcod'] = bindec(substr($ac3_header['bsi'], $offset, 8));
168	$offset += 8;
169	}
170
171	$info_ac3_raw_bsi['audprodie'] = $ac3_header['bsi']{$offset++} == '1';
172	if ($info_ac3_raw_bsi['audprodie']) {
173	$info_ac3_raw_bsi['mixlevel'] = bindec(substr($ac3_header['bsi'], $offset, 5));
174	$offset += 5;
175
176	$info_ac3_raw_bsi['roomtyp'] = bindec(substr($ac3_header['bsi'], $offset, 2));
177	$offset += 2;
178
179	$info_ac3['mixing_level'] = (80 + $info_ac3_raw_bsi['mixlevel']).'dB';
180	$info_ac3['room_type'] = getid3_ac3::AC3roomTypeLookup($info_ac3_raw_bsi['roomtyp']);
181	}
182
183	if ($info_ac3_raw_bsi['acmod'] == 0x00) {
184	// If acmod is 0, then two completely independent program channels (dual mono)
185	// are encoded into the bit stream, and are referenced as Ch1, Ch2. In this case,
186	// a number of additional items are present in BSI or audblk to fully describe Ch2.
187
188
189	// This indicates how far the average dialogue level is below digital 100 percent. Valid values are 131.
190	// 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.
191	$info_ac3_raw_bsi['dialnorm2'] = bindec(substr($ac3_header['bsi'], $offset, 5));
192	$offset += 5;
193
194	$info_ac3['dialogue_normalization2'] = '-'.$info_ac3_raw_bsi['dialnorm2'].'dB';
195
196	$info_ac3_raw_bsi['compre_flag2'] = $ac3_header['bsi']{$offset++} == '1';
197	if ($info_ac3_raw_bsi['compre_flag2']) {
198	$info_ac3_raw_bsi['compr2'] = bindec(substr($ac3_header['bsi'], $offset, 8));
199	$offset += 8;
200
201	$info_ac3['heavy_compression2'] = getid3_ac3::AC3heavyCompression($info_ac3_raw_bsi['compr2']);
202	}
203
204	$info_ac3_raw_bsi['langcode_flag2'] = $ac3_header['bsi']{$offset++} == '1';
205	if ($info_ac3_raw_bsi['langcode_flag2']) {
206	$info_ac3_raw_bsi['langcod2'] = bindec(substr($ac3_header['bsi'], $offset, 8));
207	$offset += 8;
208	}
209
210	$info_ac3_raw_bsi['audprodie2'] = $ac3_header['bsi']{$offset++} == '1';
211	if ($info_ac3_raw_bsi['audprodie2']) {
212	$info_ac3_raw_bsi['mixlevel2'] = bindec(substr($ac3_header['bsi'], $offset, 5));
213	$offset += 5;
214
215	$info_ac3_raw_bsi['roomtyp2'] = bindec(substr($ac3_header['bsi'], $offset, 2));
216	$offset += 2;
217
218	$info_ac3['mixing_level2'] = (80 + $info_ac3_raw_bsi['mixlevel2']).'dB';
219	$info_ac3['room_type2'] = getid3_ac3::AC3roomTypeLookup($info_ac3_raw_bsi['roomtyp2']);
220	}
221
222	}
223
224	$info_ac3_raw_bsi['copyright'] = $ac3_header['bsi']{$offset++} == '1';
225
226	$info_ac3_raw_bsi['original'] = $ac3_header['bsi']{$offset++} == '1';
227
228	$info_ac3_raw_bsi['timecode1_flag'] = $ac3_header['bsi']{$offset++} == '1';
229	if ($info_ac3_raw_bsi['timecode1_flag']) {
230	$info_ac3_raw_bsi['timecode1'] = bindec(substr($ac3_header['bsi'], $offset, 14));
231	$offset += 14;
232	}
233
234	$info_ac3_raw_bsi['timecode2_flag'] = $ac3_header['bsi']{$offset++} == '1';
235	if ($info_ac3_raw_bsi['timecode2_flag']) {
236	$info_ac3_raw_bsi['timecode2'] = bindec(substr($ac3_header['bsi'], $offset, 14));
237	$offset += 14;
238	}
239
240	$info_ac3_raw_bsi['addbsi_flag'] = $ac3_header['bsi']{$offset++} == '1';
241	if ($info_ac3_raw_bsi['addbsi_flag']) {
242	$info_ac3_raw_bsi['addbsi_length'] = bindec(substr($ac3_header['bsi'], $offset, 6));
243	$offset += 6;
244
245	$ac3_header['bsi'] .= getid3_lib::BigEndian2Bin($this->fread($info_ac3_raw_bsi['addbsi_length']));
246
247	$info_ac3_raw_bsi['addbsi_data'] = substr($ac3_header['bsi'], 119, $info_ac3_raw_bsi['addbsi_length'] * 8);
248	}
249
250	return true;
251	}
252
253
254
255	public static function AC3sampleRateCodeLookup($fscod) {
256
257	static $lookup = array (
258	0 => 48000,
259	1 => 44100,
260	2 => 32000,
261	3 => 'reserved' // If the reserved code is indicated, the decoder should not attempt to decode audio and should mute.
262	);
263	return (isset($lookup[$fscod]) ? $lookup[$fscod] : false);
264	}
265
266
267
268	public static function AC3serviceTypeLookup($bsmod, $acmod) {
269
270	static $lookup = array (
271	0 => 'main audio service: complete main (CM)',
272	1 => 'main audio service: music and effects (ME)',
273	2 => 'associated service: visually impaired (VI)',
274	3 => 'associated service: hearing impaired (HI)',
275	4 => 'associated service: dialogue (D)',
276	5 => 'associated service: commentary (C)',
277	6 => 'associated service: emergency (E)',
278	7 => 'main audio service: karaoke'
279	);
280
281	if ($bsmod == 7 && $acmod == 1) {
282	return 'associated service: voice over (VO)';
283	}
284
285	return (isset($lookup[$bsmod]) ? $lookup[$bsmod] : false);
286	}
287
288
289
290	public static function AC3audioCodingModeLookup($acmod) {
291
292	// array (channel configuration, # channels (not incl LFE), channel order)
293	static $lookup = array (
294	0 => array ('channel_config'=>'1+1', 'num_channels'=>2, 'channel_order'=>'Ch1,Ch2'),
295	1 => array ('channel_config'=>'1/0', 'num_channels'=>1, 'channel_order'=>'C'),
296	2 => array ('channel_config'=>'2/0', 'num_channels'=>2, 'channel_order'=>'L,R'),
297	3 => array ('channel_config'=>'3/0', 'num_channels'=>3, 'channel_order'=>'L,C,R'),
298	4 => array ('channel_config'=>'2/1', 'num_channels'=>3, 'channel_order'=>'L,R,S'),
299	5 => array ('channel_config'=>'3/1', 'num_channels'=>4, 'channel_order'=>'L,C,R,S'),
300	6 => array ('channel_config'=>'2/2', 'num_channels'=>4, 'channel_order'=>'L,R,SL,SR'),
301	7 => array ('channel_config'=>'3/2', 'num_channels'=>5, 'channel_order'=>'L,C,R,SL,SR')
302	);
303	return (isset($lookup[$acmod]) ? $lookup[$acmod] : false);
304	}
305
306
307
308	public static function AC3centerMixLevelLookup($cmixlev) {
309
310	static $lookup;
311	if (!@$lookup) {
312	$lookup = array (
313	0 => pow(2, -3.0 / 6), // 0.707 (3.0 dB)
314	1 => pow(2, -4.5 / 6), // 0.595 (4.5 dB)
315	2 => pow(2, -6.0 / 6), // 0.500 (6.0 dB)
316	3 => 'reserved'
317	);
318	}
319	return (isset($lookup[$cmixlev]) ? $lookup[$cmixlev] : false);
320	}
321
322
323
324	public static function AC3surroundMixLevelLookup($surmixlev) {
325
326	static $lookup;
327	if (!@$lookup) {
328	$lookup = array (
329	0 => pow(2, -3.0 / 6),
330	1 => pow(2, -6.0 / 6),
331	2 => 0,
332	3 => 'reserved'
333	);
334	}
335	return (isset($lookup[$surmixlev]) ? $lookup[$surmixlev] : false);
336	}
337
338
339
340	public static function AC3dolbySurroundModeLookup($dsurmod) {
341
342	static $lookup = array (
343	0 => 'not indicated',
344	1 => 'Not Dolby Surround encoded',
345	2 => 'Dolby Surround encoded',
346	3 => 'reserved'
347	);
348	return (isset($lookup[$dsurmod]) ? $lookup[$dsurmod] : false);
349	}
350
351
352
353	public static function AC3channelsEnabledLookup($acmod, $lfeon) {
354
355	return array (
356	'ch1' => $acmod == 0,
357	'ch2' => $acmod == 0,
358	'left' => $acmod > 1,
359	'right' => $acmod > 1,
360	'center' => (bool)($acmod & 0x01),
361	'surround_mono' => $acmod == 4 \|\| $acmod == 5,
362	'surround_left' => $acmod == 6 \|\| $acmod == 7,
363	'surround_right' => $acmod == 6 \|\| $acmod == 7,
364	'lfe' => $lfeon
365	);
366	}
367
368
369
370	public static function AC3heavyCompression($compre) {
371
372	// The first four bits indicate gain changes in 6.02dB increments which can be
373	// implemented with an arithmetic shift operation. The following four bits
374	// indicate linear gain changes, and require a 5-bit multiply.
375	// We will represent the two 4-bit fields of compr as follows:
376	// X0 X1 X2 X3 . Y4 Y5 Y6 Y7
377	// The meaning of the X values is most simply described by considering X to represent a 4-bit
378	// signed integer with values from 8 to +7. The gain indicated by X is then (X + 1) * 6.02 dB. The
379	// following table shows this in detail.
380
381	// Meaning of 4 msb of compr
382	// 7 +48.16 dB
383	// 6 +42.14 dB
384	// 5 +36.12 dB
385	// 4 +30.10 dB
386	// 3 +24.08 dB
387	// 2 +18.06 dB
388	// 1 +12.04 dB
389	// 0 +6.02 dB
390	// -1 0 dB
391	// -2 6.02 dB
392	// -3 12.04 dB
393	// -4 18.06 dB
394	// -5 24.08 dB
395	// -6 30.10 dB
396	// -7 36.12 dB
397	// -8 42.14 dB
398
399	$fourbit = str_pad(decbin(($compre & 0xF0) >> 4), 4, '0', STR_PAD_LEFT);
400	if ($fourbit{0} == '1') {
401	$log_gain = -8 + bindec(substr($fourbit, 1));
402	} else {
403	$log_gain = bindec(substr($fourbit, 1));
404	}
405	$log_gain = ($log_gain + 1) * (20 * log10(2));
406
407	// The value of Y is a linear representation of a gain change of up to 6 dB. Y is considered to
408	// be an unsigned fractional integer, with a leading value of 1, or: 0.1 Y4 Y5 Y6 Y7 (base 2). Y can
409	// represent values between 0.111112 (or 31/32) and 0.100002 (or 1/2). Thus, Y can represent gain
410	// changes from 0.28 dB to 6.02 dB.
411
412	$lin_gain = (16 + ($compre & 0x0F)) / 32;
413
414	// The combination of X and Y values allows compr to indicate gain changes from
415	// 48.16 0.28 = +47.89 dB, to
416	// 42.14 6.02 = 48.16 dB.
417
418	return $log_gain - $lin_gain;
419	}
420
421
422
423	public static function AC3roomTypeLookup($roomtyp) {
424
425	static $lookup = array (
426	0 => 'not indicated',
427	1 => 'large room, X curve monitor',
428	2 => 'small room, flat monitor',
429	3 => 'reserved'
430	);
431	return (isset($lookup[$roomtyp]) ? $lookup[$roomtyp] : false);
432	}
433
434
435
436	public static function AC3frameSizeLookup($frmsizecod, $fscod) {
437
438	$padding = (bool)($frmsizecod % 2);
439	$frame_size_id = floor($frmsizecod / 2);
440
441	static $lookup = array (
442	0 => array (128, 138, 192),
443	1 => array (40, 160, 174, 240),
444	2 => array (48, 192, 208, 288),
445	3 => array (56, 224, 242, 336),
446	4 => array (64, 256, 278, 384),
447	5 => array (80, 320, 348, 480),
448	6 => array (96, 384, 416, 576),
449	7 => array (112, 448, 486, 672),
450	8 => array (128, 512, 556, 768),
451	9 => array (160, 640, 696, 960),
452	10 => array (192, 768, 834, 1152),
453	11 => array (224, 896, 974, 1344),
454	12 => array (256, 1024, 1114, 1536),
455	13 => array (320, 1280, 1392, 1920),
456	14 => array (384, 1536, 1670, 2304),
457	15 => array (448, 1792, 1950, 2688),
458	16 => array (512, 2048, 2228, 3072),
459	17 => array (576, 2304, 2506, 3456),
460	18 => array (640, 2560, 2786, 3840)
461	);
462	if (($fscod == 1) && $padding) {
463	// frame lengths are padded by 1 word (16 bits) at 44100
464	$lookup[$frmsizecod] += 2;
465	}
466	return (isset($lookup[$frame_size_id][$fscod]) ? $lookup[$frame_size_id][$fscod] : false);
467	}
468
469
470
471	public static function AC3bitrateLookup($frmsizecod) {
472
473	static $lookup = array (
474	0 => 32000,
475	1 => 40000,
476	2 => 48000,
477	3 => 56000,
478	4 => 64000,
479	5 => 80000,
480	6 => 96000,
481	7 => 112000,
482	8 => 128000,
483	9 => 160000,
484	10 => 192000,
485	11 => 224000,
486	12 => 256000,
487	13 => 320000,
488	14 => 384000,
489	15 => 448000,
490	16 => 512000,
491	17 => 576000,
492	18 => 640000
493	);
494	$frame_size_id = floor($frmsizecod / 2);
495	return (isset($lookup[$frame_size_id]) ? $lookup[$frame_size_id] : false);
496	}
497
498	}
499
500	?>

Note: See TracBrowser for help on using the repository browser.

Download in other formats: