ILIAS  release_5-2 Revision v5.2.25-18-g3f80b828510
Public Member Functions | Static Public Member Functions | Private Member Functions | Private Attributes
GetId3\Module\Audio\Ac3 Class Reference

GetId3() by James Heinrich info@.nosp@m.geti.nosp@m.d3.or.nosp@m.g //. More...

+ Inheritance diagram for GetId3\Module\Audio\Ac3:
+ Collaboration diagram for GetId3\Module\Audio\Ac3:

Public Member Functions

 analyze ()
 
- Public Member Functions inherited from GetId3\Handler\BaseHandler
 __construct (GetId3Core $getid3, $call_module=null)
 
 analyze ()
 Analyze from file pointer. More...
 
 AnalyzeString (&$string)
 Analyze from string instead. More...
 
 saveAttachment (&$ThisFileInfoIndex, $filename, $offset, $length)
 

Static Public Member Functions

static sampleRateCodeLookup ($fscod)
 array $AC3sampleRateCodeLookup More...
 
static serviceTypeLookup ($bsmod, $acmod)
 array $AC3serviceTypeLookup More...
 
static audioCodingModeLookup ($acmod)
 array $AC3audioCodingModeLookup More...
 
static centerMixLevelLookup ($cmixlev)
 type $AC3centerMixLevelLookup More...
 
static surroundMixLevelLookup ($surmixlev)
 type $AC3surroundMixLevelLookup More...
 
static dolbySurroundModeLookup ($dsurmod)
 array $AC3dolbySurroundModeLookup More...
 
static channelsEnabledLookup ($acmod, $lfeon)
 
static heavyCompression ($compre)
 
static roomTypeLookup ($roomtyp)
 array $AC3roomTypeLookup More...
 
static frameSizeLookup ($frmsizecod, $fscod)
 array $AC3frameSizeLookup More...
 
static bitrateLookup ($frmsizecod)
 array $AC3bitrateLookup More...
 

Private Member Functions

 readHeaderBSI ($length)
 

Private Attributes

 $AC3header = array()
 
 $BSIoffset = 0
 

Additional Inherited Members

- Protected Member Functions inherited from GetId3\Handler\BaseHandler
 ftell ()
 
 fread ($bytes)
 
 fseek ($bytes, $whence=SEEK_SET)
 
 feof ()
 
 isDependencyFor ($module)
 
 error ($text)
 
 warning ($text)
 
- Protected Attributes inherited from GetId3\Handler\BaseHandler
 $getid3
 
 $data_string_flag = false
 
 $data_string = ''
 
 $data_string_position = 0
 
 $data_string_length = 0
 

Detailed Description

GetId3() by James Heinrich info@.nosp@m.geti.nosp@m.d3.or.nosp@m.g //.

module for analyzing AC-3 (aka Dolby Digital) audio files

Author
James Heinrich info@.nosp@m.geti.nosp@m.d3.or.nosp@m.g http://www.getid3.org

Definition at line 29 of file Ac3.php.

Member Function Documentation

◆ analyze()

GetId3\Module\Audio\Ac3::analyze ( )
Returns
boolean

AH

Definition at line 47 of file Ac3.php.

References $info, array, GetId3\Lib\Helper\BigEndian2Bin(), GetId3\Handler\BaseHandler\error(), GetId3\Handler\BaseHandler\fread(), GetId3\Handler\BaseHandler\fseek(), GetId3\Handler\BaseHandler\isDependencyFor(), GetId3\Lib\Helper\LittleEndian2Int(), GetId3\Lib\Helper\PrintHexBytes(), and GetId3\Module\Audio\Ac3\readHeaderBSI().

48  {
49  $info = &$this->getid3->info;
50 
52  $info['ac3']['raw']['bsi'] = array();
53  $thisfile_ac3 = &$info['ac3'];
54  $thisfile_ac3_raw = &$thisfile_ac3['raw'];
55  $thisfile_ac3_raw_bsi = &$thisfile_ac3_raw['bsi'];
56 
57  // http://www.atsc.org/standards/a_52a.pdf
58 
59  $info['fileformat'] = 'ac3';
60 
61  // An AC-3 serial coded audio bit stream is made up of a sequence of synchronization frames
62  // Each synchronization frame contains 6 coded audio blocks (AB), each of which represent 256
63  // new audio samples per channel. A synchronization information (SI) header at the beginning
64  // of each frame contains information needed to acquire and maintain synchronization. A
65  // bit stream information (BSI) header follows SI, and contains parameters describing the coded
66  // audio service. The coded audio blocks may be followed by an auxiliary data (Aux) field. At the
67  // end of each frame is an error check field that includes a CRC word for error detection. An
68  // additional CRC word is located in the SI header, the use of which, by a decoder, is optional.
69  //
70  // syncinfo() | bsi() | AB0 | AB1 | AB2 | AB3 | AB4 | AB5 | Aux | CRC
71 
72  // syncinfo() {
73  // syncword 16
74  // crc1 16
75  // fscod 2
76  // frmsizecod 6
77  // } /* end of syncinfo */
78 
79  $this->fseek($info['avdataoffset']);
80  $this->AC3header['syncinfo'] = $this->fread(5);
81 
82  $magic = "\x0B\x77";
83 
84  if (strpos($this->AC3header['syncinfo'], $magic) === 0) {
85  $thisfile_ac3_raw['synchinfo']['synchword'] = $magic;
86  $offset = 2;
87  } else {
88  if (!$this->isDependencyFor('matroska')) {
89  unset($info['fileformat'], $info['ac3']);
90 
91  return $this->error('Expecting "'.Helper::PrintHexBytes($magic).'" at offset '.$info['avdataoffset'].', found "'.Helper::PrintHexBytes(substr($this->AC3header['syncinfo'], 0, 2)).'"');
92  }
93  $offset = 0;
94  $this->fseek(-2, SEEK_CUR);
95  }
96 
97  $info['audio']['dataformat'] = 'ac3';
98  $info['audio']['bitrate_mode'] = 'cbr';
99  $info['audio']['lossless'] = false;
100 
101  $thisfile_ac3_raw['synchinfo']['crc1'] = Helper::LittleEndian2Int(substr($this->AC3header['syncinfo'], $offset, 2));
102  $ac3_synchinfo_fscod_frmsizecod = Helper::LittleEndian2Int(substr($this->AC3header['syncinfo'], ($offset + 2), 1));
103  $thisfile_ac3_raw['synchinfo']['fscod'] = ($ac3_synchinfo_fscod_frmsizecod & 0xC0) >> 6;
104  $thisfile_ac3_raw['synchinfo']['frmsizecod'] = ($ac3_synchinfo_fscod_frmsizecod & 0x3F);
105 
106  $thisfile_ac3['sample_rate'] = self::sampleRateCodeLookup($thisfile_ac3_raw['synchinfo']['fscod']);
107  if ($thisfile_ac3_raw['synchinfo']['fscod'] <= 3) {
108  $info['audio']['sample_rate'] = $thisfile_ac3['sample_rate'];
109  }
110 
111  $thisfile_ac3['frame_length'] = self::frameSizeLookup($thisfile_ac3_raw['synchinfo']['frmsizecod'], $thisfile_ac3_raw['synchinfo']['fscod']);
112  $thisfile_ac3['bitrate'] = self::bitrateLookup($thisfile_ac3_raw['synchinfo']['frmsizecod']);
113  $info['audio']['bitrate'] = $thisfile_ac3['bitrate'];
114 
115  $this->AC3header['bsi'] = Helper::BigEndian2Bin($this->fread(15));
116  $ac3_bsi_offset = 0;
117 
118  $thisfile_ac3_raw_bsi['bsid'] = $this->readHeaderBSI(5);
119  if ($thisfile_ac3_raw_bsi['bsid'] > 8) {
120  // Decoders which can decode version 8 will thus be able to decode version numbers less than 8.
121  // If this standard is extended by the addition of additional elements or features, a value of bsid greater than 8 will be used.
122  // Decoders built to this version of the standard will not be able to decode versions with bsid greater than 8.
123  $this->error('Bit stream identification is version '.$thisfile_ac3_raw_bsi['bsid'].', but GetId3Core() only understands up to version 8');
124  unset($info['ac3']);
125 
126  return false;
127  }
128 
129  $thisfile_ac3_raw_bsi['bsmod'] = $this->readHeaderBSI(3);
130  $thisfile_ac3_raw_bsi['acmod'] = $this->readHeaderBSI(3);
131 
132  $thisfile_ac3['service_type'] = self::serviceTypeLookup($thisfile_ac3_raw_bsi['bsmod'], $thisfile_ac3_raw_bsi['acmod']);
133  $ac3_coding_mode = self::audioCodingModeLookup($thisfile_ac3_raw_bsi['acmod']);
134  foreach ($ac3_coding_mode as $key => $value) {
135  $thisfile_ac3[$key] = $value;
136  }
137  switch ($thisfile_ac3_raw_bsi['acmod']) {
138  case 0:
139  case 1:
140  $info['audio']['channelmode'] = 'mono';
141  break;
142  case 3:
143  case 4:
144  $info['audio']['channelmode'] = 'stereo';
145  break;
146  default:
147  $info['audio']['channelmode'] = 'surround';
148  break;
149  }
150  $info['audio']['channels'] = $thisfile_ac3['num_channels'];
151 
152  if ($thisfile_ac3_raw_bsi['acmod'] & 0x01) {
153  // If the lsb of acmod is a 1, center channel is in use and cmixlev follows in the bit stream.
154  $thisfile_ac3_raw_bsi['cmixlev'] = $this->readHeaderBSI(2);
155  $thisfile_ac3['center_mix_level'] = self::centerMixLevelLookup($thisfile_ac3_raw_bsi['cmixlev']);
156  }
157 
158  if ($thisfile_ac3_raw_bsi['acmod'] & 0x04) {
159  // If the msb of acmod is a 1, surround channels are in use and surmixlev follows in the bit stream.
160  $thisfile_ac3_raw_bsi['surmixlev'] = $this->readHeaderBSI(2);
161  $thisfile_ac3['surround_mix_level'] = self::surroundMixLevelLookup($thisfile_ac3_raw_bsi['surmixlev']);
162  }
163 
164  if ($thisfile_ac3_raw_bsi['acmod'] == 0x02) {
165  // When operating in the two channel mode, this 2-bit code indicates whether or not the program has been encoded in Dolby Surround.
166  $thisfile_ac3_raw_bsi['dsurmod'] = $this->readHeaderBSI(2);
167  $thisfile_ac3['dolby_surround_mode'] = self::dolbySurroundModeLookup($thisfile_ac3_raw_bsi['dsurmod']);
168  }
169 
170  $thisfile_ac3_raw_bsi['lfeon'] = (bool) $this->readHeaderBSI(1);
171  $thisfile_ac3['lfe_enabled'] = $thisfile_ac3_raw_bsi['lfeon'];
172  if ($thisfile_ac3_raw_bsi['lfeon']) {
173  //$info['audio']['channels']++;
174  $info['audio']['channels'] .= '.1';
175  }
176 
177  $thisfile_ac3['channels_enabled'] = self::channelsEnabledLookup($thisfile_ac3_raw_bsi['acmod'], $thisfile_ac3_raw_bsi['lfeon']);
178 
179  // This indicates how far the average dialogue level is below digital 100 percent. Valid values are 1–31.
180  // 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.
181  $thisfile_ac3_raw_bsi['dialnorm'] = $this->readHeaderBSI(5);
182  $thisfile_ac3['dialogue_normalization'] = '-'.$thisfile_ac3_raw_bsi['dialnorm'].'dB';
183 
184  $thisfile_ac3_raw_bsi['compre_flag'] = (bool) $this->readHeaderBSI(1);
185  if ($thisfile_ac3_raw_bsi['compre_flag']) {
186  $thisfile_ac3_raw_bsi['compr'] = $this->readHeaderBSI(8);
187  $thisfile_ac3['heavy_compression'] = self::heavyCompression($thisfile_ac3_raw_bsi['compr']);
188  }
189 
190  $thisfile_ac3_raw_bsi['langcode_flag'] = (bool) $this->readHeaderBSI(1);
191  if ($thisfile_ac3_raw_bsi['langcode_flag']) {
192  $thisfile_ac3_raw_bsi['langcod'] = $this->readHeaderBSI(8);
193  }
194 
195  $thisfile_ac3_raw_bsi['audprodie'] = (bool) $this->readHeaderBSI(1);
196  if ($thisfile_ac3_raw_bsi['audprodie']) {
197  $thisfile_ac3_raw_bsi['mixlevel'] = $this->readHeaderBSI(5);
198  $thisfile_ac3_raw_bsi['roomtyp'] = $this->readHeaderBSI(2);
199 
200  $thisfile_ac3['mixing_level'] = (80 + $thisfile_ac3_raw_bsi['mixlevel']).'dB';
201  $thisfile_ac3['room_type'] = self::roomTypeLookup($thisfile_ac3_raw_bsi['roomtyp']);
202  }
203 
204  if ($thisfile_ac3_raw_bsi['acmod'] == 0x00) {
205  // If acmod is 0, then two completely independent program channels (dual mono)
206  // are encoded into the bit stream, and are referenced as Ch1, Ch2. In this case,
207  // a number of additional items are present in BSI or audblk to fully describe Ch2.
208 
209  // This indicates how far the average dialogue level is below digital 100 percent. Valid values are 1–31.
210  // 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.
211  $thisfile_ac3_raw_bsi['dialnorm2'] = $this->readHeaderBSI(5);
212  $thisfile_ac3['dialogue_normalization2'] = '-'.$thisfile_ac3_raw_bsi['dialnorm2'].'dB';
213 
214  $thisfile_ac3_raw_bsi['compre_flag2'] = (bool) $this->readHeaderBSI(1);
215  if ($thisfile_ac3_raw_bsi['compre_flag2']) {
216  $thisfile_ac3_raw_bsi['compr2'] = $this->readHeaderBSI(8);
217  $thisfile_ac3['heavy_compression2'] = self::heavyCompression($thisfile_ac3_raw_bsi['compr2']);
218  }
219 
220  $thisfile_ac3_raw_bsi['langcode_flag2'] = (bool) $this->readHeaderBSI(1);
221  if ($thisfile_ac3_raw_bsi['langcode_flag2']) {
222  $thisfile_ac3_raw_bsi['langcod2'] = $this->readHeaderBSI(8);
223  }
224 
225  $thisfile_ac3_raw_bsi['audprodie2'] = (bool) $this->readHeaderBSI(1);
226  if ($thisfile_ac3_raw_bsi['audprodie2']) {
227  $thisfile_ac3_raw_bsi['mixlevel2'] = $this->readHeaderBSI(5);
228  $thisfile_ac3_raw_bsi['roomtyp2'] = $this->readHeaderBSI(2);
229 
230  $thisfile_ac3['mixing_level2'] = (80 + $thisfile_ac3_raw_bsi['mixlevel2']).'dB';
231  $thisfile_ac3['room_type2'] = self::roomTypeLookup($thisfile_ac3_raw_bsi['roomtyp2']);
232  }
233 
234  }
235 
236  $thisfile_ac3_raw_bsi['copyright'] = (bool) $this->readHeaderBSI(1);
237 
238  $thisfile_ac3_raw_bsi['original'] = (bool) $this->readHeaderBSI(1);
239 
240  $thisfile_ac3_raw_bsi['timecode1_flag'] = (bool) $this->readHeaderBSI(1);
241  if ($thisfile_ac3_raw_bsi['timecode1_flag']) {
242  $thisfile_ac3_raw_bsi['timecode1'] = $this->readHeaderBSI(14);
243  }
244 
245  $thisfile_ac3_raw_bsi['timecode2_flag'] = (bool) $this->readHeaderBSI(1);
246  if ($thisfile_ac3_raw_bsi['timecode2_flag']) {
247  $thisfile_ac3_raw_bsi['timecode2'] = $this->readHeaderBSI(14);
248  }
249 
250  $thisfile_ac3_raw_bsi['addbsi_flag'] = (bool) $this->readHeaderBSI(1);
251  if ($thisfile_ac3_raw_bsi['addbsi_flag']) {
252  $thisfile_ac3_raw_bsi['addbsi_length'] = $this->readHeaderBSI(6);
253 
254  $this->AC3header['bsi'] .= Helper::BigEndian2Bin($this->fread($thisfile_ac3_raw_bsi['addbsi_length']));
255 
256  $thisfile_ac3_raw_bsi['addbsi_data'] = substr($this->AC3header['bsi'], $this->BSIoffset, $thisfile_ac3_raw_bsi['addbsi_length'] * 8);
257  $this->BSIoffset += $thisfile_ac3_raw_bsi['addbsi_length'] * 8;
258  }
259 
260  return true;
261  }
GetId3\Lib\Helper\BigEndian2Bin
static BigEndian2Bin($byteword)
Definition: Helper.php:423
GetId3\Lib\Helper\PrintHexBytes
static PrintHexBytes($string, $hex=true, $spaces=true, $htmlencoding='UTF-8')
Definition: Helper.php:36
GetId3\Module\Audio\Ac3\readHeaderBSI
readHeaderBSI($length)
Definition: Ac3.php:268
GetId3\Handler\BaseHandler\fseek
fseek($bytes, $whence=SEEK_SET)
Definition: BaseHandler.php:148
$info
$info
Definition: example_052.php:80
array
Create styles array
The data for the language used.
Definition: 40duplicateStyle.php:19
GetId3\Lib\Helper\LittleEndian2Int
static LittleEndian2Int($byteword, $signed=false)
Definition: Helper.php:413
+ Here is the call graph for this function:

◆ audioCodingModeLookup()

static GetId3\Module\Audio\Ac3::audioCodingModeLookup (   $acmod)
static

array $AC3audioCodingModeLookup

Parameters
type$acmod
Returns
type

Definition at line 330 of file Ac3.php.

References array.

331  {
332  static $AC3audioCodingModeLookup = array();
333  if (empty($AC3audioCodingModeLookup)) {
334  // array(channel configuration, # channels (not incl LFE), channel order)
335  $AC3audioCodingModeLookup = array (
336  0 => array('channel_config'=>'1+1', 'num_channels'=>2, 'channel_order'=>'Ch1,Ch2'),
337  1 => array('channel_config'=>'1/0', 'num_channels'=>1, 'channel_order'=>'C'),
338  2 => array('channel_config'=>'2/0', 'num_channels'=>2, 'channel_order'=>'L,R'),
339  3 => array('channel_config'=>'3/0', 'num_channels'=>3, 'channel_order'=>'L,C,R'),
340  4 => array('channel_config'=>'2/1', 'num_channels'=>3, 'channel_order'=>'L,R,S'),
341  5 => array('channel_config'=>'3/1', 'num_channels'=>4, 'channel_order'=>'L,C,R,S'),
342  6 => array('channel_config'=>'2/2', 'num_channels'=>4, 'channel_order'=>'L,R,SL,SR'),
343  7 => array('channel_config'=>'3/2', 'num_channels'=>5, 'channel_order'=>'L,C,R,SL,SR')
344  );
345  }
346 
347  return (isset($AC3audioCodingModeLookup[$acmod]) ? $AC3audioCodingModeLookup[$acmod] : false);
348  }
array
Create styles array
The data for the language used.
Definition: 40duplicateStyle.php:19

◆ bitrateLookup()

static GetId3\Module\Audio\Ac3::bitrateLookup (   $frmsizecod)
static

array $AC3bitrateLookup

Parameters
type$frmsizecod
Returns
type

Definition at line 566 of file Ac3.php.

References array.

567  {
568  $framesizeid = floor($frmsizecod / 2);
569 
570  static $AC3bitrateLookup = array(
571  0 => 32000,
572  1 => 40000,
573  2 => 48000,
574  3 => 56000,
575  4 => 64000,
576  5 => 80000,
577  6 => 96000,
578  7 => 112000,
579  8 => 128000,
580  9 => 160000,
581  10 => 192000,
582  11 => 224000,
583  12 => 256000,
584  13 => 320000,
585  14 => 384000,
586  15 => 448000,
587  16 => 512000,
588  17 => 576000,
589  18 => 640000
590  );
591 
592  return (isset($AC3bitrateLookup[$framesizeid]) ? $AC3bitrateLookup[$framesizeid] : false);
593  }
array
Create styles array
The data for the language used.
Definition: 40duplicateStyle.php:19

◆ centerMixLevelLookup()

static GetId3\Module\Audio\Ac3::centerMixLevelLookup (   $cmixlev)
static

type $AC3centerMixLevelLookup

Parameters
type$cmixlev
Returns
type

Definition at line 356 of file Ac3.php.

References array.

357  {
358  static $AC3centerMixLevelLookup;
359  if (empty($AC3centerMixLevelLookup)) {
360  $AC3centerMixLevelLookup = array(
361  0 => pow(2, -3.0 / 6), // 0.707 (–3.0 dB)
362  1 => pow(2, -4.5 / 6), // 0.595 (–4.5 dB)
363  2 => pow(2, -6.0 / 6), // 0.500 (–6.0 dB)
364  3 => 'reserved'
365  );
366  }
367 
368  return (isset($AC3centerMixLevelLookup[$cmixlev]) ? $AC3centerMixLevelLookup[$cmixlev] : false);
369  }
array
Create styles array
The data for the language used.
Definition: 40duplicateStyle.php:19

◆ channelsEnabledLookup()

static GetId3\Module\Audio\Ac3::channelsEnabledLookup (   $acmod,
  $lfeon 
)
static
Parameters
type$acmod
type$lfeon
Returns
boolean

Definition at line 416 of file Ac3.php.

References array.

417  {
418  $AC3channelsEnabledLookup = array(
419  'ch1'=>(bool) ($acmod == 0),
420  'ch2'=>(bool) ($acmod == 0),
421  'left'=>(bool) ($acmod > 1),
422  'right'=>(bool) ($acmod > 1),
423  'center'=>(bool) ($acmod & 0x01),
424  'surround_mono'=>false,
425  'surround_left'=>false,
426  'surround_right'=>false,
427  'lfe'=>$lfeon);
428  switch ($acmod) {
429  case 4:
430  case 5:
431  $AC3channelsEnabledLookup['surround_mono'] = true;
432  break;
433  case 6:
434  case 7:
435  $AC3channelsEnabledLookup['surround_left'] = true;
436  $AC3channelsEnabledLookup['surround_right'] = true;
437  break;
438  }
439 
440  return $AC3channelsEnabledLookup;
441  }
array
Create styles array
The data for the language used.
Definition: 40duplicateStyle.php:19

◆ dolbySurroundModeLookup()

static GetId3\Module\Audio\Ac3::dolbySurroundModeLookup (   $dsurmod)
static

array $AC3dolbySurroundModeLookup

Parameters
type$dsurmod
Returns
type

Definition at line 398 of file Ac3.php.

References array.

399  {
400  static $AC3dolbySurroundModeLookup = array(
401  0 => 'not indicated',
402  1 => 'Not Dolby Surround encoded',
403  2 => 'Dolby Surround encoded',
404  3 => 'reserved'
405  );
406 
407  return (isset($AC3dolbySurroundModeLookup[$dsurmod]) ? $AC3dolbySurroundModeLookup[$dsurmod] : false);
408  }
array
Create styles array
The data for the language used.
Definition: 40duplicateStyle.php:19

◆ frameSizeLookup()

static GetId3\Module\Audio\Ac3::frameSizeLookup (   $frmsizecod,
  $fscod 
)
static

array $AC3frameSizeLookup

Parameters
type$frmsizecod
type$fscod
Returns
type

Definition at line 523 of file Ac3.php.

References array.

524  {
525  $padding = (bool) ($frmsizecod % 2);
526  $framesizeid = floor($frmsizecod / 2);
527 
528  static $AC3frameSizeLookup = array();
529  if (empty($AC3frameSizeLookup)) {
530  $AC3frameSizeLookup = array (
531  0 => array(128, 138, 192),
532  1 => array(40, 160, 174, 240),
533  2 => array(48, 192, 208, 288),
534  3 => array(56, 224, 242, 336),
535  4 => array(64, 256, 278, 384),
536  5 => array(80, 320, 348, 480),
537  6 => array(96, 384, 416, 576),
538  7 => array(112, 448, 486, 672),
539  8 => array(128, 512, 556, 768),
540  9 => array(160, 640, 696, 960),
541  10 => array(192, 768, 834, 1152),
542  11 => array(224, 896, 974, 1344),
543  12 => array(256, 1024, 1114, 1536),
544  13 => array(320, 1280, 1392, 1920),
545  14 => array(384, 1536, 1670, 2304),
546  15 => array(448, 1792, 1950, 2688),
547  16 => array(512, 2048, 2228, 3072),
548  17 => array(576, 2304, 2506, 3456),
549  18 => array(640, 2560, 2786, 3840)
550  );
551  }
552  if (($fscod == 1) && $padding) {
553  // frame lengths are padded by 1 word (16 bits) at 44100
554  $AC3frameSizeLookup[$frmsizecod] += 2;
555  }
556 
557  return (isset($AC3frameSizeLookup[$framesizeid][$fscod]) ? $AC3frameSizeLookup[$framesizeid][$fscod] : false);
558  }
array
Create styles array
The data for the language used.
Definition: 40duplicateStyle.php:19

◆ heavyCompression()

static GetId3\Module\Audio\Ac3::heavyCompression (   $compre)
static
Parameters
type$compre
Returns
type

Definition at line 448 of file Ac3.php.

References GetId3\Lib\Helper\RGADamplitude2dB().

449  {
450  // The first four bits indicate gain changes in 6.02dB increments which can be
451  // implemented with an arithmetic shift operation. The following four bits
452  // indicate linear gain changes, and require a 5-bit multiply.
453  // We will represent the two 4-bit fields of compr as follows:
454  // X0 X1 X2 X3 . Y4 Y5 Y6 Y7
455  // The meaning of the X values is most simply described by considering X to represent a 4-bit
456  // signed integer with values from –8 to +7. The gain indicated by X is then (X + 1) * 6.02 dB. The
457  // following table shows this in detail.
458 
459  // Meaning of 4 msb of compr
460  // 7 +48.16 dB
461  // 6 +42.14 dB
462  // 5 +36.12 dB
463  // 4 +30.10 dB
464  // 3 +24.08 dB
465  // 2 +18.06 dB
466  // 1 +12.04 dB
467  // 0 +6.02 dB
468  // -1 0 dB
469  // -2 –6.02 dB
470  // -3 –12.04 dB
471  // -4 –18.06 dB
472  // -5 –24.08 dB
473  // -6 –30.10 dB
474  // -7 –36.12 dB
475  // -8 –42.14 dB
476 
477  $fourbit = str_pad(decbin(($compre & 0xF0) >> 4), 4, '0', STR_PAD_LEFT);
478  if ($fourbit{0} == '1') {
479  $log_gain = -8 + bindec(substr($fourbit, 1));
480  } else {
481  $log_gain = bindec(substr($fourbit, 1));
482  }
483  $log_gain = ($log_gain + 1) * Helper::RGADamplitude2dB(2);
484 
485  // The value of Y is a linear representation of a gain change of up to –6 dB. Y is considered to
486  // be an unsigned fractional integer, with a leading value of 1, or: 0.1 Y4 Y5 Y6 Y7 (base 2). Y can
487  // represent values between 0.111112 (or 31/32) and 0.100002 (or 1/2). Thus, Y can represent gain
488  // changes from –0.28 dB to –6.02 dB.
489 
490  $lin_gain = (16 + ($compre & 0x0F)) / 32;
491 
492  // The combination of X and Y values allows compr to indicate gain changes from
493  // 48.16 – 0.28 = +47.89 dB, to
494  // –42.14 – 6.02 = –48.16 dB.
495  return $log_gain - $lin_gain;
496  }
GetId3\Lib\Helper\RGADamplitude2dB
static RGADamplitude2dB($amplitude)
Definition: Helper.php:1610
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◆ readHeaderBSI()

GetId3\Module\Audio\Ac3::readHeaderBSI (   $length)
private
Parameters
type$length
Returns
type

Definition at line 268 of file Ac3.php.

References $data.

Referenced by GetId3\Module\Audio\Ac3\analyze().

269  {
270  $data = substr($this->AC3header['bsi'], $this->BSIoffset, $length);
271  $this->BSIoffset += $length;
272 
273  return bindec($data);
274  }
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◆ roomTypeLookup()

static GetId3\Module\Audio\Ac3::roomTypeLookup (   $roomtyp)
static

array $AC3roomTypeLookup

Parameters
type$roomtyp
Returns
type

Definition at line 504 of file Ac3.php.

References array.

505  {
506  static $AC3roomTypeLookup = array(
507  0 => 'not indicated',
508  1 => 'large room, X curve monitor',
509  2 => 'small room, flat monitor',
510  3 => 'reserved'
511  );
512 
513  return (isset($AC3roomTypeLookup[$roomtyp]) ? $AC3roomTypeLookup[$roomtyp] : false);
514  }
array
Create styles array
The data for the language used.
Definition: 40duplicateStyle.php:19

◆ sampleRateCodeLookup()

static GetId3\Module\Audio\Ac3::sampleRateCodeLookup (   $fscod)
static

array $AC3sampleRateCodeLookup

Parameters
type$fscod
Returns
type

Definition at line 282 of file Ac3.php.

References array.

283  {
284  static $AC3sampleRateCodeLookup = array(
285  0 => 48000,
286  1 => 44100,
287  2 => 32000,
288  3 => 'reserved' // If the reserved code is indicated, the decoder should not attempt to decode audio and should mute.
289  );
290 
291  return (isset($AC3sampleRateCodeLookup[$fscod]) ? $AC3sampleRateCodeLookup[$fscod] : false);
292  }
array
Create styles array
The data for the language used.
Definition: 40duplicateStyle.php:19

◆ serviceTypeLookup()

static GetId3\Module\Audio\Ac3::serviceTypeLookup (   $bsmod,
  $acmod 
)
static

array $AC3serviceTypeLookup

Parameters
type$bsmod
type$acmod
Returns
type

Definition at line 301 of file Ac3.php.

References array.

302  {
303  static $AC3serviceTypeLookup = array();
304  if (empty($AC3serviceTypeLookup)) {
305  for ($i = 0; $i <= 7; $i++) {
306  $AC3serviceTypeLookup[0][$i] = 'main audio service: complete main (CM)';
307  $AC3serviceTypeLookup[1][$i] = 'main audio service: music and effects (ME)';
308  $AC3serviceTypeLookup[2][$i] = 'associated service: visually impaired (VI)';
309  $AC3serviceTypeLookup[3][$i] = 'associated service: hearing impaired (HI)';
310  $AC3serviceTypeLookup[4][$i] = 'associated service: dialogue (D)';
311  $AC3serviceTypeLookup[5][$i] = 'associated service: commentary (C)';
312  $AC3serviceTypeLookup[6][$i] = 'associated service: emergency (E)';
313  }
314 
315  $AC3serviceTypeLookup[7][1] = 'associated service: voice over (VO)';
316  for ($i = 2; $i <= 7; $i++) {
317  $AC3serviceTypeLookup[7][$i] = 'main audio service: karaoke';
318  }
319  }
320 
321  return (isset($AC3serviceTypeLookup[$bsmod][$acmod]) ? $AC3serviceTypeLookup[$bsmod][$acmod] : false);
322  }
array
Create styles array
The data for the language used.
Definition: 40duplicateStyle.php:19

◆ surroundMixLevelLookup()

static GetId3\Module\Audio\Ac3::surroundMixLevelLookup (   $surmixlev)
static

type $AC3surroundMixLevelLookup

Parameters
type$surmixlev
Returns
type

Definition at line 377 of file Ac3.php.

References array.

378  {
379  static $AC3surroundMixLevelLookup;
380  if (empty($AC3surroundMixLevelLookup)) {
381  $AC3surroundMixLevelLookup = array(
382  0 => pow(2, -3.0 / 6),
383  1 => pow(2, -6.0 / 6),
384  2 => 0,
385  3 => 'reserved'
386  );
387  }
388 
389  return (isset($AC3surroundMixLevelLookup[$surmixlev]) ? $AC3surroundMixLevelLookup[$surmixlev] : false);
390  }
array
Create styles array
The data for the language used.
Definition: 40duplicateStyle.php:19

Field Documentation

◆ $AC3header

GetId3\Module\Audio\Ac3::$AC3header = array()
private

Definition at line 35 of file Ac3.php.

◆ $BSIoffset

GetId3\Module\Audio\Ac3::$BSIoffset = 0
private

Definition at line 41 of file Ac3.php.

The documentation for this class was generated from the following file: