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Code source de LifeType 1.2.4 |
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 1–31. 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 1–31. 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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| Généré le : Mon Nov 26 21:04:15 2007 | par Balluche grâce à PHPXref 0.7 |
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