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module.audio.ac3.php @ 3544

Last change on this file since 3544 was 3544, checked in by vdigital, 15 years ago
Change: getid3 upgraded to -> 1.7.9
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1	<?php
2	/////////////////////////////////////////////////////////////////
3	/// getID3() by James Heinrich <info@getid3.org> //
4	// available at http://getid3.sourceforge.net //
5	// or http://www.getid3.org //
6	/////////////////////////////////////////////////////////////////
7	// See readme.txt for more details //
8	/////////////////////////////////////////////////////////////////
9	// //
10	// module.audio.ac3.php //
11	// module for analyzing AC-3 (aka Dolby Digital) audio files //
12	// dependencies: NONE //
13	// ///
14	/////////////////////////////////////////////////////////////////
15
16
17	class getid3_ac3
18	{
19
20	function getid3_ac3(&$fd, &$ThisFileInfo) {
21
22	///AH
23	$ThisFileInfo['ac3']['raw']['bsi'] = array();
24	$thisfile_ac3 = &$ThisFileInfo['ac3'];
25	$thisfile_ac3_raw = &$thisfile_ac3['raw'];
26	$thisfile_ac3_raw_bsi = &$thisfile_ac3_raw['bsi'];
27
28
29	// http://www.atsc.org/standards/a_52a.pdf
30
31	$ThisFileInfo['fileformat'] = 'ac3';
32	$ThisFileInfo['audio']['dataformat'] = 'ac3';
33	$ThisFileInfo['audio']['bitrate_mode'] = 'cbr';
34	$ThisFileInfo['audio']['lossless'] = false;
35
36	// An AC-3 serial coded audio bit stream is made up of a sequence of synchronization frames
37	// Each synchronization frame contains 6 coded audio blocks (AB), each of which represent 256
38	// new audio samples per channel. A synchronization information (SI) header at the beginning
39	// of each frame contains information needed to acquire and maintain synchronization. A
40	// bit stream information (BSI) header follows SI, and contains parameters describing the coded
41	// audio service. The coded audio blocks may be followed by an auxiliary data (Aux) field. At the
42	// end of each frame is an error check field that includes a CRC word for error detection. An
43	// additional CRC word is located in the SI header, the use of which, by a decoder, is optional.
44	//
45	// syncinfo() \| bsi() \| AB0 \| AB1 \| AB2 \| AB3 \| AB4 \| AB5 \| Aux \| CRC
46
47	fseek($fd, $ThisFileInfo['avdataoffset'], SEEK_SET);
48	$AC3header['syncinfo'] = fread($fd, 5);
49	$thisfile_ac3_raw['synchinfo']['synchword'] = substr($AC3header['syncinfo'], 0, 2);
50
51	if ($thisfile_ac3_raw['synchinfo']['synchword'] != "\x0B\x77") {
52
53	$ThisFileInfo['error'][] = 'Expecting "\x0B\x77" at offset '.$ThisFileInfo['avdataoffset'].', found \x'.strtoupper(dechex($AC3header['syncinfo']{0})).'\x'.strtoupper(dechex($AC3header['syncinfo']{1})).' instead';
54	unset($thisfile_ac3);
55	return false;
56
57	} else {
58
59	// syncinfo() {
60	// syncword 16
61	// crc1 16
62	// fscod 2
63	// frmsizecod 6
64	// } /* end of syncinfo */
65
66	$thisfile_ac3_raw['synchinfo']['crc1'] = getid3_lib::LittleEndian2Int(substr($AC3header['syncinfo'], 2, 2));
67	$ac3_synchinfo_fscod_frmsizecod = getid3_lib::LittleEndian2Int(substr($AC3header['syncinfo'], 4, 1));
68	$thisfile_ac3_raw['synchinfo']['fscod'] = ($ac3_synchinfo_fscod_frmsizecod & 0xC0) >> 6;
69	$thisfile_ac3_raw['synchinfo']['frmsizecod'] = ($ac3_synchinfo_fscod_frmsizecod & 0x3F);
70
71	$thisfile_ac3['sample_rate'] = $this->AC3sampleRateCodeLookup($thisfile_ac3_raw['synchinfo']['fscod']);
72	if ($thisfile_ac3_raw['synchinfo']['fscod'] <= 3) {
73	$ThisFileInfo['audio']['sample_rate'] = $thisfile_ac3['sample_rate'];
74	}
75
76	$thisfile_ac3['frame_length'] = $this->AC3frameSizeLookup($thisfile_ac3_raw['synchinfo']['frmsizecod'], $thisfile_ac3_raw['synchinfo']['fscod']);
77	$thisfile_ac3['bitrate'] = $this->AC3bitrateLookup($thisfile_ac3_raw['synchinfo']['frmsizecod']);
78	$ThisFileInfo['audio']['bitrate'] = $thisfile_ac3['bitrate'];
79
80	$AC3header['bsi'] = getid3_lib::BigEndian2Bin(fread($fd, 15));
81	$ac3_bsi_offset = 0;
82
83	$thisfile_ac3_raw_bsi['bsid'] = bindec(substr($AC3header['bsi'], $ac3_bsi_offset, 5));
84	$ac3_bsi_offset += 5;
85	if ($thisfile_ac3_raw_bsi['bsid'] > 8) {
86	// Decoders which can decode version 8 will thus be able to decode version numbers less than 8.
87	// If this standard is extended by the addition of additional elements or features, a value of bsid greater than 8 will be used.
88	// Decoders built to this version of the standard will not be able to decode versions with bsid greater than 8.
89	$ThisFileInfo['error'][] = 'Bit stream identification is version '.$thisfile_ac3_raw_bsi['bsid'].', but getID3() only understands up to version 8';
90	unset($thisfile_ac3);
91	return false;
92	}
93
94	$thisfile_ac3_raw_bsi['bsmod'] = bindec(substr($AC3header['bsi'], $ac3_bsi_offset, 3));
95	$ac3_bsi_offset += 3;
96	$thisfile_ac3_raw_bsi['acmod'] = bindec(substr($AC3header['bsi'], $ac3_bsi_offset, 3));
97	$ac3_bsi_offset += 3;
98
99	$thisfile_ac3['service_type'] = $this->AC3serviceTypeLookup($thisfile_ac3_raw_bsi['bsmod'], $thisfile_ac3_raw_bsi['acmod']);
100	$ac3_coding_mode = $this->AC3audioCodingModeLookup($thisfile_ac3_raw_bsi['acmod']);
101	foreach($ac3_coding_mode as $key => $value) {
102	$thisfile_ac3[$key] = $value;
103	}
104	switch ($thisfile_ac3_raw_bsi['acmod']) {
105	case 0:
106	case 1:
107	$ThisFileInfo['audio']['channelmode'] = 'mono';
108	break;
109	case 3:
110	case 4:
111	$ThisFileInfo['audio']['channelmode'] = 'stereo';
112	break;
113	default:
114	$ThisFileInfo['audio']['channelmode'] = 'surround';
115	break;
116	}
117	$ThisFileInfo['audio']['channels'] = $thisfile_ac3['num_channels'];
118
119	if ($thisfile_ac3_raw_bsi['acmod'] & 0x01) {
120	// If the lsb of acmod is a 1, center channel is in use and cmixlev follows in the bit stream.
121	$thisfile_ac3_raw_bsi['cmixlev'] = bindec(substr($AC3header['bsi'], $ac3_bsi_offset, 2));
122	$ac3_bsi_offset += 2;
123	$thisfile_ac3['center_mix_level'] = $this->AC3centerMixLevelLookup($thisfile_ac3_raw_bsi['cmixlev']);
124	}
125
126	if ($thisfile_ac3_raw_bsi['acmod'] & 0x04) {
127	// If the msb of acmod is a 1, surround channels are in use and surmixlev follows in the bit stream.
128	$thisfile_ac3_raw_bsi['surmixlev'] = bindec(substr($AC3header['bsi'], $ac3_bsi_offset, 2));
129	$ac3_bsi_offset += 2;
130	$thisfile_ac3['surround_mix_level'] = $this->AC3surroundMixLevelLookup($thisfile_ac3_raw_bsi['surmixlev']);
131	}
132
133	if ($thisfile_ac3_raw_bsi['acmod'] == 0x02) {
134	// When operating in the two channel mode, this 2-bit code indicates whether or not the program has been encoded in Dolby Surround.
135	$thisfile_ac3_raw_bsi['dsurmod'] = bindec(substr($AC3header['bsi'], $ac3_bsi_offset, 2));
136	$ac3_bsi_offset += 2;
137	$thisfile_ac3['dolby_surround_mode'] = $this->AC3dolbySurroundModeLookup($thisfile_ac3_raw_bsi['dsurmod']);
138	}
139
140	$thisfile_ac3_raw_bsi['lfeon'] = (bool) bindec(substr($AC3header['bsi'], $ac3_bsi_offset, 1));
141	$ac3_bsi_offset += 1;
142	$thisfile_ac3['lfe_enabled'] = $thisfile_ac3_raw_bsi['lfeon'];
143	if ($thisfile_ac3_raw_bsi['lfeon']) {
144	//$ThisFileInfo['audio']['channels']++;
145	$ThisFileInfo['audio']['channels'] .= '.1';
146	}
147
148	$thisfile_ac3['channels_enabled'] = $this->AC3channelsEnabledLookup($thisfile_ac3_raw_bsi['acmod'], $thisfile_ac3_raw_bsi['lfeon']);
149
150	// This indicates how far the average dialogue level is below digital 100 percent. Valid values are 131.
151	// 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.
152	$thisfile_ac3_raw_bsi['dialnorm'] = bindec(substr($AC3header['bsi'], $ac3_bsi_offset, 5));
153	$ac3_bsi_offset += 5;
154	$thisfile_ac3['dialogue_normalization'] = '-'.$thisfile_ac3_raw_bsi['dialnorm'].'dB';
155
156	$thisfile_ac3_raw_bsi['compre_flag'] = (bool) bindec(substr($AC3header['bsi'], $ac3_bsi_offset, 1));
157	$ac3_bsi_offset += 1;
158	if ($thisfile_ac3_raw_bsi['compre_flag']) {
159	$thisfile_ac3_raw_bsi['compr'] = bindec(substr($AC3header['bsi'], $ac3_bsi_offset, 8));
160	$ac3_bsi_offset += 8;
161	$thisfile_ac3['heavy_compression'] = $this->AC3heavyCompression($thisfile_ac3_raw_bsi['compr']);
162	}
163
164	$thisfile_ac3_raw_bsi['langcode_flag'] = (bool) bindec(substr($AC3header['bsi'], $ac3_bsi_offset, 1));
165	$ac3_bsi_offset += 1;
166	if ($thisfile_ac3_raw_bsi['langcode_flag']) {
167	$thisfile_ac3_raw_bsi['langcod'] = bindec(substr($AC3header['bsi'], $ac3_bsi_offset, 8));
168	$ac3_bsi_offset += 8;
169	}
170
171	$thisfile_ac3_raw_bsi['audprodie'] = (bool) bindec(substr($AC3header['bsi'], $ac3_bsi_offset, 1));
172	$ac3_bsi_offset += 1;
173	if ($thisfile_ac3_raw_bsi['audprodie']) {
174	$thisfile_ac3_raw_bsi['mixlevel'] = bindec(substr($AC3header['bsi'], $ac3_bsi_offset, 5));
175	$ac3_bsi_offset += 5;
176	$thisfile_ac3_raw_bsi['roomtyp'] = bindec(substr($AC3header['bsi'], $ac3_bsi_offset, 2));
177	$ac3_bsi_offset += 2;
178
179	$thisfile_ac3['mixing_level'] = (80 + $thisfile_ac3_raw_bsi['mixlevel']).'dB';
180	$thisfile_ac3['room_type'] = $this->AC3roomTypeLookup($thisfile_ac3_raw_bsi['roomtyp']);
181	}
182
183	if ($thisfile_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	$thisfile_ac3_raw_bsi['dialnorm2'] = bindec(substr($AC3header['bsi'], $ac3_bsi_offset, 5));
192	$ac3_bsi_offset += 5;
193	$thisfile_ac3['dialogue_normalization2'] = '-'.$thisfile_ac3_raw_bsi['dialnorm2'].'dB';
194
195	$thisfile_ac3_raw_bsi['compre_flag2'] = (bool) bindec(substr($AC3header['bsi'], $ac3_bsi_offset, 1));
196	$ac3_bsi_offset += 1;
197	if ($thisfile_ac3_raw_bsi['compre_flag2']) {
198	$thisfile_ac3_raw_bsi['compr2'] = bindec(substr($AC3header['bsi'], $ac3_bsi_offset, 8));
199	$ac3_bsi_offset += 8;
200	$thisfile_ac3['heavy_compression2'] = $this->AC3heavyCompression($thisfile_ac3_raw_bsi['compr2']);
201	}
202
203	$thisfile_ac3_raw_bsi['langcode_flag2'] = (bool) bindec(substr($AC3header['bsi'], $ac3_bsi_offset, 1));
204	$ac3_bsi_offset += 1;
205	if ($thisfile_ac3_raw_bsi['langcode_flag2']) {
206	$thisfile_ac3_raw_bsi['langcod2'] = bindec(substr($AC3header['bsi'], $ac3_bsi_offset, 8));
207	$ac3_bsi_offset += 8;
208	}
209
210	$thisfile_ac3_raw_bsi['audprodie2'] = (bool) bindec(substr($AC3header['bsi'], $ac3_bsi_offset, 1));
211	$ac3_bsi_offset += 1;
212	if ($thisfile_ac3_raw_bsi['audprodie2']) {
213	$thisfile_ac3_raw_bsi['mixlevel2'] = bindec(substr($AC3header['bsi'], $ac3_bsi_offset, 5));
214	$ac3_bsi_offset += 5;
215	$thisfile_ac3_raw_bsi['roomtyp2'] = bindec(substr($AC3header['bsi'], $ac3_bsi_offset, 2));
216	$ac3_bsi_offset += 2;
217
218	$thisfile_ac3['mixing_level2'] = (80 + $thisfile_ac3_raw_bsi['mixlevel2']).'dB';
219	$thisfile_ac3['room_type2'] = $this->AC3roomTypeLookup($thisfile_ac3_raw_bsi['roomtyp2']);
220	}
221
222	}
223
224	$thisfile_ac3_raw_bsi['copyright'] = (bool) bindec(substr($AC3header['bsi'], $ac3_bsi_offset, 1));
225	$ac3_bsi_offset += 1;
226
227	$thisfile_ac3_raw_bsi['original'] = (bool) bindec(substr($AC3header['bsi'], $ac3_bsi_offset, 1));
228	$ac3_bsi_offset += 1;
229
230	$thisfile_ac3_raw_bsi['timecode1_flag'] = (bool) bindec(substr($AC3header['bsi'], $ac3_bsi_offset, 1));
231	$ac3_bsi_offset += 1;
232	if ($thisfile_ac3_raw_bsi['timecode1_flag']) {
233	$thisfile_ac3_raw_bsi['timecode1'] = bindec(substr($AC3header['bsi'], $ac3_bsi_offset, 14));
234	$ac3_bsi_offset += 14;
235	}
236
237	$thisfile_ac3_raw_bsi['timecode2_flag'] = (bool) bindec(substr($AC3header['bsi'], $ac3_bsi_offset, 1));
238	$ac3_bsi_offset += 1;
239	if ($thisfile_ac3_raw_bsi['timecode2_flag']) {
240	$thisfile_ac3_raw_bsi['timecode2'] = bindec(substr($AC3header['bsi'], $ac3_bsi_offset, 14));
241	$ac3_bsi_offset += 14;
242	}
243
244	$thisfile_ac3_raw_bsi['addbsi_flag'] = (bool) bindec(substr($AC3header['bsi'], $ac3_bsi_offset, 1));
245	$ac3_bsi_offset += 1;
246	if ($thisfile_ac3_raw_bsi['addbsi_flag']) {
247	$thisfile_ac3_raw_bsi['addbsi_length'] = bindec(substr($AC3header['bsi'], $ac3_bsi_offset, 6));
248	$ac3_bsi_offset += 6;
249
250	$AC3header['bsi'] .= getid3_lib::BigEndian2Bin(fread($fd, $thisfile_ac3_raw_bsi['addbsi_length']));
251
252	$thisfile_ac3_raw_bsi['addbsi_data'] = substr($AC3header['bsi'], $ac3_bsi_offset, $thisfile_ac3_raw_bsi['addbsi_length'] * 8);
253	$ac3_bsi_offset += $thisfile_ac3_raw_bsi['addbsi_length'] * 8;
254	}
255
256	}
257
258	return true;
259	}
260
261
262	function AC3sampleRateCodeLookup($fscod) {
263	static $AC3sampleRateCodeLookup = array(
264	0 => 48000,
265	1 => 44100,
266	2 => 32000,
267	3 => 'reserved' // If the reserved code is indicated, the decoder should not attempt to decode audio and should mute.
268	);
269	return (isset($AC3sampleRateCodeLookup[$fscod]) ? $AC3sampleRateCodeLookup[$fscod] : false);
270	}
271
272	function AC3serviceTypeLookup($bsmod, $acmod) {
273	static $AC3serviceTypeLookup = array();
274	if (empty($AC3serviceTypeLookup)) {
275	for ($i = 0; $i <= 7; $i++) {
276	$AC3serviceTypeLookup[0][$i] = 'main audio service: complete main (CM)';
277	$AC3serviceTypeLookup[1][$i] = 'main audio service: music and effects (ME)';
278	$AC3serviceTypeLookup[2][$i] = 'associated service: visually impaired (VI)';
279	$AC3serviceTypeLookup[3][$i] = 'associated service: hearing impaired (HI)';
280	$AC3serviceTypeLookup[4][$i] = 'associated service: dialogue (D)';
281	$AC3serviceTypeLookup[5][$i] = 'associated service: commentary (C)';
282	$AC3serviceTypeLookup[6][$i] = 'associated service: emergency (E)';
283	}
284
285	$AC3serviceTypeLookup[7][1] = 'associated service: voice over (VO)';
286	for ($i = 2; $i <= 7; $i++) {
287	$AC3serviceTypeLookup[7][$i] = 'main audio service: karaoke';
288	}
289	}
290	return (isset($AC3serviceTypeLookup[$bsmod][$acmod]) ? $AC3serviceTypeLookup[$bsmod][$acmod] : false);
291	}
292
293	function AC3audioCodingModeLookup($acmod) {
294	static $AC3audioCodingModeLookup = array();
295	if (empty($AC3audioCodingModeLookup)) {
296	// array(channel configuration, # channels (not incl LFE), channel order)
297	$AC3audioCodingModeLookup = array (
298	0 => array('channel_config'=>'1+1', 'num_channels'=>2, 'channel_order'=>'Ch1,Ch2'),
299	1 => array('channel_config'=>'1/0', 'num_channels'=>1, 'channel_order'=>'C'),
300	2 => array('channel_config'=>'2/0', 'num_channels'=>2, 'channel_order'=>'L,R'),
301	3 => array('channel_config'=>'3/0', 'num_channels'=>3, 'channel_order'=>'L,C,R'),
302	4 => array('channel_config'=>'2/1', 'num_channels'=>3, 'channel_order'=>'L,R,S'),
303	5 => array('channel_config'=>'3/1', 'num_channels'=>4, 'channel_order'=>'L,C,R,S'),
304	6 => array('channel_config'=>'2/2', 'num_channels'=>4, 'channel_order'=>'L,R,SL,SR'),
305	7 => array('channel_config'=>'3/2', 'num_channels'=>5, 'channel_order'=>'L,C,R,SL,SR')
306	);
307	}
308	return (isset($AC3audioCodingModeLookup[$acmod]) ? $AC3audioCodingModeLookup[$acmod] : false);
309	}
310
311	function AC3centerMixLevelLookup($cmixlev) {
312	static $AC3centerMixLevelLookup;
313	if (empty($AC3centerMixLevelLookup)) {
314	$AC3centerMixLevelLookup = array(
315	0 => pow(2, -3.0 / 6), // 0.707 (3.0 dB)
316	1 => pow(2, -4.5 / 6), // 0.595 (4.5 dB)
317	2 => pow(2, -6.0 / 6), // 0.500 (6.0 dB)
318	3 => 'reserved'
319	);
320	}
321	return (isset($AC3centerMixLevelLookup[$cmixlev]) ? $AC3centerMixLevelLookup[$cmixlev] : false);
322	}
323
324	function AC3surroundMixLevelLookup($surmixlev) {
325	static $AC3surroundMixLevelLookup;
326	if (empty($AC3surroundMixLevelLookup)) {
327	$AC3surroundMixLevelLookup = array(
328	0 => pow(2, -3.0 / 6),
329	1 => pow(2, -6.0 / 6),
330	2 => 0,
331	3 => 'reserved'
332	);
333	}
334	return (isset($AC3surroundMixLevelLookup[$surmixlev]) ? $AC3surroundMixLevelLookup[$surmixlev] : false);
335	}
336
337	function AC3dolbySurroundModeLookup($dsurmod) {
338	static $AC3dolbySurroundModeLookup = array(
339	0 => 'not indicated',
340	1 => 'Not Dolby Surround encoded',
341	2 => 'Dolby Surround encoded',
342	3 => 'reserved'
343	);
344	return (isset($AC3dolbySurroundModeLookup[$dsurmod]) ? $AC3dolbySurroundModeLookup[$dsurmod] : false);
345	}
346
347	function AC3channelsEnabledLookup($acmod, $lfeon) {
348	$AC3channelsEnabledLookup = array(
349	'ch1'=>(bool) ($acmod == 0),
350	'ch2'=>(bool) ($acmod == 0),
351	'left'=>(bool) ($acmod > 1),
352	'right'=>(bool) ($acmod > 1),
353	'center'=>(bool) ($acmod & 0x01),
354	'surround_mono'=>false,
355	'surround_left'=>false,
356	'surround_right'=>false,
357	'lfe'=>$lfeon);
358	switch ($acmod) {
359	case 4:
360	case 5:
361	$AC3channelsEnabledLookup['surround_mono'] = true;
362	break;
363	case 6:
364	case 7:
365	$AC3channelsEnabledLookup['surround_left'] = true;
366	$AC3channelsEnabledLookup['surround_right'] = true;
367	break;
368	}
369	return $AC3channelsEnabledLookup;
370	}
371
372	function AC3heavyCompression($compre) {
373	// The first four bits indicate gain changes in 6.02dB increments which can be
374	// implemented with an arithmetic shift operation. The following four bits
375	// indicate linear gain changes, and require a 5-bit multiply.
376	// We will represent the two 4-bit fields of compr as follows:
377	// X0 X1 X2 X3 . Y4 Y5 Y6 Y7
378	// The meaning of the X values is most simply described by considering X to represent a 4-bit
379	// signed integer with values from 8 to +7. The gain indicated by X is then (X + 1) * 6.02 dB. The
380	// following table shows this in detail.
381
382	// Meaning of 4 msb of compr
383	// 7 +48.16 dB
384	// 6 +42.14 dB
385	// 5 +36.12 dB
386	// 4 +30.10 dB
387	// 3 +24.08 dB
388	// 2 +18.06 dB
389	// 1 +12.04 dB
390	// 0 +6.02 dB
391	// -1 0 dB
392	// -2 6.02 dB
393	// -3 12.04 dB
394	// -4 18.06 dB
395	// -5 24.08 dB
396	// -6 30.10 dB
397	// -7 36.12 dB
398	// -8 42.14 dB
399
400	$fourbit = str_pad(decbin(($compre & 0xF0) >> 4), 4, '0', STR_PAD_LEFT);
401	if ($fourbit{0} == '1') {
402	$log_gain = -8 + bindec(substr($fourbit, 1));
403	} else {
404	$log_gain = bindec(substr($fourbit, 1));
405	}
406	$log_gain = ($log_gain + 1) * getid3_lib::RGADamplitude2dB(2);
407
408	// The value of Y is a linear representation of a gain change of up to 6 dB. Y is considered to
409	// be an unsigned fractional integer, with a leading value of 1, or: 0.1 Y4 Y5 Y6 Y7 (base 2). Y can
410	// represent values between 0.111112 (or 31/32) and 0.100002 (or 1/2). Thus, Y can represent gain
411	// changes from 0.28 dB to 6.02 dB.
412
413	$lin_gain = (16 + ($compre & 0x0F)) / 32;
414
415	// The combination of X and Y values allows compr to indicate gain changes from
416	// 48.16 0.28 = +47.89 dB, to
417	// 42.14 6.02 = 48.16 dB.
418
419	return $log_gain - $lin_gain;
420	}
421
422	function AC3roomTypeLookup($roomtyp) {
423	static $AC3roomTypeLookup = array(
424	0 => 'not indicated',
425	1 => 'large room, X curve monitor',
426	2 => 'small room, flat monitor',
427	3 => 'reserved'
428	);
429	return (isset($AC3roomTypeLookup[$roomtyp]) ? $AC3roomTypeLookup[$roomtyp] : false);
430	}
431
432	function AC3frameSizeLookup($frmsizecod, $fscod) {
433	$padding = (bool) ($frmsizecod % 2);
434	$framesizeid = floor($frmsizecod / 2);
435
436	static $AC3frameSizeLookup = array();
437	if (empty($AC3frameSizeLookup)) {
438	$AC3frameSizeLookup = array (
439	0 => array(128, 138, 192),
440	1 => array(40, 160, 174, 240),
441	2 => array(48, 192, 208, 288),
442	3 => array(56, 224, 242, 336),
443	4 => array(64, 256, 278, 384),
444	5 => array(80, 320, 348, 480),
445	6 => array(96, 384, 416, 576),
446	7 => array(112, 448, 486, 672),
447	8 => array(128, 512, 556, 768),
448	9 => array(160, 640, 696, 960),
449	10 => array(192, 768, 834, 1152),
450	11 => array(224, 896, 974, 1344),
451	12 => array(256, 1024, 1114, 1536),
452	13 => array(320, 1280, 1392, 1920),
453	14 => array(384, 1536, 1670, 2304),
454	15 => array(448, 1792, 1950, 2688),
455	16 => array(512, 2048, 2228, 3072),
456	17 => array(576, 2304, 2506, 3456),
457	18 => array(640, 2560, 2786, 3840)
458	);
459	}
460	if (($fscod == 1) && $padding) {
461	// frame lengths are padded by 1 word (16 bits) at 44100
462	$AC3frameSizeLookup[$frmsizecod] += 2;
463	}
464	return (isset($AC3frameSizeLookup[$framesizeid][$fscod]) ? $AC3frameSizeLookup[$framesizeid][$fscod] : false);
465	}
466
467	function AC3bitrateLookup($frmsizecod) {
468	$framesizeid = floor($frmsizecod / 2);
469
470	static $AC3bitrateLookup = array(
471	0 => 32000,
472	1 => 40000,
473	2 => 48000,
474	3 => 56000,
475	4 => 64000,
476	5 => 80000,
477	6 => 96000,
478	7 => 112000,
479	8 => 128000,
480	9 => 160000,
481	10 => 192000,
482	11 => 224000,
483	12 => 256000,
484	13 => 320000,
485	14 => 384000,
486	15 => 448000,
487	16 => 512000,
488	17 => 576000,
489	18 => 640000
490	);
491	return (isset($AC3bitrateLookup[$framesizeid]) ? $AC3bitrateLookup[$framesizeid] : false);
492	}
493
494
495	}
496
497	?>

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source: extensions/charlies_content/getid3/getid3/module.audio.ac3.php @ 3544

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