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Source: /modules/getid3/module.audio.aac.php - 513 lines - 24875 bytes - Summary - Text - Print

   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  //          also https://github.com/JamesHeinrich/getID3       //
   7  /////////////////////////////////////////////////////////////////
   8  // See readme.txt for more details                             //
   9  /////////////////////////////////////////////////////////////////
  10  //                                                             //
  11  // module.audio.aac.php                                        //
  12  // module for analyzing AAC Audio files                        //
  13  // dependencies: NONE                                          //
  14  //                                                            ///
  15  /////////////////////////////////////////////////////////////////
  16  
  17  
  18  class getid3_aac extends getid3_handler
  19  {
  20  	public function Analyze() {
  21          $info = &$this->getid3->info;
  22          $this->fseek($info['avdataoffset']);
  23          if ($this->fread(4) == 'ADIF') {
  24              $this->getAACADIFheaderFilepointer();
  25          } else {
  26              $this->getAACADTSheaderFilepointer();
  27          }
  28          return true;
  29      }
  30  
  31  
  32  
  33  	public function getAACADIFheaderFilepointer() {
  34          $info = &$this->getid3->info;
  35          $info['fileformat']          = 'aac';
  36          $info['audio']['dataformat'] = 'aac';
  37          $info['audio']['lossless']   = false;
  38  
  39          $this->fseek($info['avdataoffset']);
  40          $AACheader = $this->fread(1024);
  41          $offset    = 0;
  42  
  43          if (substr($AACheader, 0, 4) == 'ADIF') {
  44  
  45              // http://faac.sourceforge.net/wiki/index.php?page=ADIF
  46  
  47              // http://libmpeg.org/mpeg4/doc/w2203tfs.pdf
  48              // adif_header() {
  49              //     adif_id                                32
  50              //     copyright_id_present                    1
  51              //     if( copyright_id_present )
  52              //         copyright_id                       72
  53              //     original_copy                           1
  54              //     home                                    1
  55              //     bitstream_type                          1
  56              //     bitrate                                23
  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()
  62              //     }
  63              // }
  64  
  65              $AACheaderBitstream = getid3_lib::BigEndian2Bin($AACheader);
  66              $bitoffset          = 0;
  67  
  68              $info['aac']['header_type']                   = 'ADIF';
  69              $bitoffset += 32;
  70              $info['aac']['header']['mpeg_version']        = 4;
  71  
  72              $info['aac']['header']['copyright']           = (bool) (substr($AACheaderBitstream, $bitoffset, 1) == '1');
  73              $bitoffset += 1;
  74              if ($info['aac']['header']['copyright']) {
  75                  $info['aac']['header']['copyright_id']    = getid3_lib::Bin2String(substr($AACheaderBitstream, $bitoffset, 72));
  76                  $bitoffset += 72;
  77              }
  78              $info['aac']['header']['original_copy']       = (bool) (substr($AACheaderBitstream, $bitoffset, 1) == '1');
  79              $bitoffset += 1;
  80              $info['aac']['header']['home']                = (bool) (substr($AACheaderBitstream, $bitoffset, 1) == '1');
  81              $bitoffset += 1;
  82              $info['aac']['header']['is_vbr']              = (bool) (substr($AACheaderBitstream, $bitoffset, 1) == '1');
  83              $bitoffset += 1;
  84              if ($info['aac']['header']['is_vbr']) {
  85                  $info['audio']['bitrate_mode']            = 'vbr';
  86                  $info['aac']['header']['bitrate_max']     = getid3_lib::Bin2Dec(substr($AACheaderBitstream, $bitoffset, 23));
  87                  $bitoffset += 23;
  88              } else {
  89                  $info['audio']['bitrate_mode']            = 'cbr';
  90                  $info['aac']['header']['bitrate']         = getid3_lib::Bin2Dec(substr($AACheaderBitstream, $bitoffset, 23));
  91                  $bitoffset += 23;
  92                  $info['audio']['bitrate']                 = $info['aac']['header']['bitrate'];
  93              }
  94              if ($info['audio']['bitrate'] == 0) {
  95                  $info['error'][] = 'Corrupt AAC file: bitrate_audio == zero';
  96                  return false;
  97              }
  98              $info['aac']['header']['num_program_configs'] = 1 + getid3_lib::Bin2Dec(substr($AACheaderBitstream, $bitoffset, 4));
  99              $bitoffset += 4;
 100  
 101              for ($i = 0; $i < $info['aac']['header']['num_program_configs']; $i++) {
 102                  // http://www.audiocoding.com/wiki/index.php?page=program_config_element
 103  
 104                  // buffer_fullness                       20
 105  
 106                  // element_instance_tag                   4
 107                  // object_type                            2
 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
 125                  // }
 126                  // for (i = 0; i < num_side_channel_elements; i++) {
 127                  //     side_element_is_cpe[i]             1
 128                  //     side_element_tag_select[i]         4
 129                  // }
 130                  // for (i = 0; i < num_back_channel_elements; i++) {
 131                  //     back_element_is_cpe[i]             1
 132                  //     back_element_tag_select[i]         4
 133                  // }
 134                  // for (i = 0; i < num_lfe_channel_elements; i++) {
 135                  //     lfe_element_tag_select[i]          4
 136                  // }
 137                  // for (i = 0; i < num_assoc_data_elements; i++) {
 138                  //     assoc_data_element_tag_select[i]   4
 139                  // }
 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
 143                  // }
 144                  // byte_alignment()                       VAR
 145                  // comment_field_bytes                    8
 146                  // for (i = 0; i < comment_field_bytes; i++) {
 147                  //     comment_field_data[i]              8
 148                  // }
 149  
 150                  if (!$info['aac']['header']['is_vbr']) {
 151                      $info['aac']['program_configs'][$i]['buffer_fullness']        = getid3_lib::Bin2Dec(substr($AACheaderBitstream, $bitoffset, 20));
 152                      $bitoffset += 20;
 153                  }
 154                  $info['aac']['program_configs'][$i]['element_instance_tag']       = getid3_lib::Bin2Dec(substr($AACheaderBitstream, $bitoffset, 4));
 155                  $bitoffset += 4;
 156                  $info['aac']['program_configs'][$i]['object_type']                = getid3_lib::Bin2Dec(substr($AACheaderBitstream, $bitoffset, 2));
 157                  $bitoffset += 2;
 158                  $info['aac']['program_configs'][$i]['sampling_frequency_index']   = getid3_lib::Bin2Dec(substr($AACheaderBitstream, $bitoffset, 4));
 159                  $bitoffset += 4;
 160                  $info['aac']['program_configs'][$i]['num_front_channel_elements'] = getid3_lib::Bin2Dec(substr($AACheaderBitstream, $bitoffset, 4));
 161                  $bitoffset += 4;
 162                  $info['aac']['program_configs'][$i]['num_side_channel_elements']  = getid3_lib::Bin2Dec(substr($AACheaderBitstream, $bitoffset, 4));
 163                  $bitoffset += 4;
 164                  $info['aac']['program_configs'][$i]['num_back_channel_elements']  = getid3_lib::Bin2Dec(substr($AACheaderBitstream, $bitoffset, 4));
 165                  $bitoffset += 4;
 166                  $info['aac']['program_configs'][$i]['num_lfe_channel_elements']   = getid3_lib::Bin2Dec(substr($AACheaderBitstream, $bitoffset, 2));
 167                  $bitoffset += 2;
 168                  $info['aac']['program_configs'][$i]['num_assoc_data_elements']    = getid3_lib::Bin2Dec(substr($AACheaderBitstream, $bitoffset, 3));
 169                  $bitoffset += 3;
 170                  $info['aac']['program_configs'][$i]['num_valid_cc_elements']      = getid3_lib::Bin2Dec(substr($AACheaderBitstream, $bitoffset, 4));
 171                  $bitoffset += 4;
 172                  $info['aac']['program_configs'][$i]['mono_mixdown_present']       = (bool) getid3_lib::Bin2Dec(substr($AACheaderBitstream, $bitoffset, 1));
 173                  $bitoffset += 1;
 174                  if ($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));
 176                      $bitoffset += 4;
 177                  }
 178                  $info['aac']['program_configs'][$i]['stereo_mixdown_present']             = (bool) getid3_lib::Bin2Dec(substr($AACheaderBitstream, $bitoffset, 1));
 179                  $bitoffset += 1;
 180                  if ($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));
 182                      $bitoffset += 4;
 183                  }
 184                  $info['aac']['program_configs'][$i]['matrix_mixdown_idx_present']         = (bool) getid3_lib::Bin2Dec(substr($AACheaderBitstream, $bitoffset, 1));
 185                  $bitoffset += 1;
 186                  if ($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));
 188                      $bitoffset += 2;
 189                      $info['aac']['program_configs'][$i]['pseudo_surround_enable']         = (bool) getid3_lib::Bin2Dec(substr($AACheaderBitstream, $bitoffset, 1));
 190                      $bitoffset += 1;
 191                  }
 192                  for ($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));
 194                      $bitoffset += 1;
 195                      $info['aac']['program_configs'][$i]['front_element_tag_select'][$j] = getid3_lib::Bin2Dec(substr($AACheaderBitstream, $bitoffset, 4));
 196                      $bitoffset += 4;
 197                  }
 198                  for ($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));
 200                      $bitoffset += 1;
 201                      $info['aac']['program_configs'][$i]['side_element_tag_select'][$j] = getid3_lib::Bin2Dec(substr($AACheaderBitstream, $bitoffset, 4));
 202                      $bitoffset += 4;
 203                  }
 204                  for ($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));
 206                      $bitoffset += 1;
 207                      $info['aac']['program_configs'][$i]['back_element_tag_select'][$j] = getid3_lib::Bin2Dec(substr($AACheaderBitstream, $bitoffset, 4));
 208                      $bitoffset += 4;
 209                  }
 210                  for ($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));
 212                      $bitoffset += 4;
 213                  }
 214                  for ($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));
 216                      $bitoffset += 4;
 217                  }
 218                  for ($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));
 220                      $bitoffset += 1;
 221                      $info['aac']['program_configs'][$i]['valid_cc_element_tag_select'][$j]   = getid3_lib::Bin2Dec(substr($AACheaderBitstream, $bitoffset, 4));
 222                      $bitoffset += 4;
 223                  }
 224  
 225                  $bitoffset = ceil($bitoffset / 8) * 8;
 226  
 227                  $info['aac']['program_configs'][$i]['comment_field_bytes'] = getid3_lib::Bin2Dec(substr($AACheaderBitstream, $bitoffset, 8));
 228                  $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'];
 231  
 232  
 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'];
 239                  }
 240              }
 241              $info['playtime_seconds'] = (($info['avdataend'] - $info['avdataoffset']) * 8) / $info['audio']['bitrate'];
 242  
 243              $info['audio']['encoder_options'] = $info['aac']['header_type'].' '.$info['aac']['header']['profile'];
 244  
 245  
 246  
 247              return true;
 248  
 249          } else {
 250  
 251              unset($info['fileformat']);
 252              unset($info['aac']);
 253              $info['error'][] = 'AAC-ADIF synch not found at offset '.$info['avdataoffset'].' (expected "ADIF", found "'.substr($AACheader, 0, 4).'" instead)';
 254              return false;
 255  
 256          }
 257  
 258      }
 259  
 260  
 261  	public function getAACADTSheaderFilepointer($MaxFramesToScan=1000000, $ReturnExtendedInfo=false) {
 262          $info = &$this->getid3->info;
 263  
 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
 266  
 267  
 268          // http://faac.sourceforge.net/wiki/index.php?page=ADTS // dead link
 269          // http://wiki.multimedia.cx/index.php?title=ADTS
 270  
 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
 281          // home                                            1    usually 0
 282          // emphasis                                        2    only if ID == 0 (ie MPEG-4)  // not present in some documentation?
 283  
 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
 290  
 291          // * ADTS Error check
 292          // crc_check                                      16    only if protection_absent == 0
 293  
 294          $byteoffset  = $info['avdataoffset'];
 295          $framenumber = 0;
 296  
 297          // Init bit pattern array
 298          static $decbin = array();
 299  
 300          // Populate $bindec
 301          for ($i = 0; $i < 256; $i++) {
 302              $decbin[chr($i)] = str_pad(decbin($i), 8, '0', STR_PAD_LEFT);
 303          }
 304  
 305          // used to calculate bitrate below
 306          $BitrateCache = array();
 307  
 308  
 309          while (true) {
 310              // breaks out when end-of-file encountered, or invalid data found,
 311              // or MaxFramesToScan frames have been scanned
 312  
 313              if (!getid3_lib::intValueSupported($byteoffset)) {
 314                  $info['warning'][] = 'Unable to parse AAC file beyond '.$this->ftell().' (PHP does not support file operations beyond '.round(PHP_INT_MAX / 1073741824).'GB)';
 315                  return false;
 316              }
 317              $this->fseek($byteoffset);
 318  
 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                  $info['error'][] = 'Failed to read 7 bytes at offset '.($this->ftell() - $substringlength).' (only read '.$substringlength.' bytes)';
 324                  return false;
 325              }
 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));
 330  
 331              $info['aac']['header']['raw']['syncword']          = ($header1 & 0xFFF0) >> 4;
 332              if ($info['aac']['header']['raw']['syncword'] != 0x0FFF) {
 333                  $info['error'][] = 'Synch pattern (0x0FFF) not found at offset '.($this->ftell() - $substringlength).' (found 0x0'.strtoupper(dechex($info['aac']['header']['raw']['syncword'])).' instead)';
 334                  //if ($info['fileformat'] == 'aac') {
 335                  //    return true;
 336                  //}
 337                  unset($info['aac']);
 338                  return false;
 339              }
 340  
 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';
 346  
 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;
 350  
 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;
 360  
 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) $info['aac']['header']['raw']['copyright_start'];
 372                  }
 373  
 374                  if ($info['aac']['header']['raw']['mpeg_layer'] != 0) {
 375                      $info['warning'][] = 'Layer error - expected "0", found "'.$info['aac']['header']['raw']['mpeg_layer'].'" instead';
 376                  }
 377                  if ($info['aac']['header']['sample_frequency'] == 0) {
 378                      $info['error'][] = 'Corrupt AAC file: sample_frequency == zero';
 379                      return false;
 380                  }
 381  
 382                  $info['audio']['sample_rate'] = $info['aac']['header']['sample_frequency'];
 383                  $info['audio']['channels']    = $info['aac']['header']['channels'];
 384              }
 385  
 386              $FrameLength = ($header2 & 0x0003FFE0) >>  5;
 387  
 388              if (!isset($BitrateCache[$FrameLength])) {
 389                  $BitrateCache[$FrameLength] = ($info['aac']['header']['sample_frequency'] / 1024) * $FrameLength * 8;
 390              }
 391              getid3_lib::safe_inc($info['aac']['bitrate_distribution'][$BitrateCache[$FrameLength]], 1);
 392  
 393              $info['aac'][$framenumber]['aac_frame_length']     = $FrameLength;
 394  
 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';
 398              } else {
 399                  $info['audio']['bitrate_mode'] = 'cbr';
 400              }
 401              $info['aac'][$framenumber]['num_raw_data_blocks']  = (($header3 & 0x03) >> 0);
 402  
 403              if ($info['aac']['header']['crc_present']) {
 404                  //$info['aac'][$framenumber]['crc'] = getid3_lib::BigEndian2Int(substr($substring, 7, 2);
 405              }
 406  
 407              if (!$ReturnExtendedInfo) {
 408                  unset($info['aac'][$framenumber]);
 409              }
 410  
 411              /*
 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], $count);
 417              }
 418              ksort($info['aac']['bitrate_distribution_rounded']);
 419              */
 420  
 421              $byteoffset += $FrameLength;
 422              if ((++$framenumber < $MaxFramesToScan) && (($byteoffset + 10) < $info['avdataend'])) {
 423  
 424                  // keep scanning
 425  
 426              } else {
 427  
 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                      $info['error'][] = 'Corrupt AAC file: playtime_seconds == zero';
 432                      return false;
 433                  }
 434                  $info['audio']['bitrate']    = (($info['avdataend'] - $info['avdataoffset']) * 8) / $info['playtime_seconds'];
 435                  ksort($info['aac']['bitrate_distribution']);
 436  
 437                  $info['audio']['encoder_options'] = $info['aac']['header_type'].' '.$info['aac']['header']['profile'];
 438  
 439                  return true;
 440  
 441              }
 442          }
 443          // should never get here.
 444      }
 445  
 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              $AACsampleRateLookup[15] = 0;
 465          }
 466          return (isset($AACsampleRateLookup[$samplerateid]) ? $AACsampleRateLookup[$samplerateid] : 'invalid');
 467      }
 468  
 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              $AACprofileLookup[4][3]  = 'AAC_LTP';
 480          }
 481          return (isset($AACprofileLookup[$mpegversion][$profileid]) ? $AACprofileLookup[$mpegversion][$profileid] : 'invalid');
 482      }
 483  
 484  	public static function AACchannelCountCalculate($program_configs) {
 485          $channels = 0;
 486          for ($i = 0; $i < $program_configs['num_front_channel_elements']; $i++) {
 487              $channels++;
 488              if ($program_configs['front_element_is_cpe'][$i]) {
 489                  // each front element is channel pair (CPE = Channel Pair Element)
 490                  $channels++;
 491              }
 492          }
 493          for ($i = 0; $i < $program_configs['num_side_channel_elements']; $i++) {
 494              $channels++;
 495              if ($program_configs['side_element_is_cpe'][$i]) {
 496                  // each side element is channel pair (CPE = Channel Pair Element)
 497                  $channels++;
 498              }
 499          }
 500          for ($i = 0; $i < $program_configs['num_back_channel_elements']; $i++) {
 501              $channels++;
 502              if ($program_configs['back_element_is_cpe'][$i]) {
 503                  // each back element is channel pair (CPE = Channel Pair Element)
 504                  $channels++;
 505              }
 506          }
 507          for ($i = 0; $i < $program_configs['num_lfe_channel_elements']; $i++) {
 508              $channels++;
 509          }
 510          return $channels;
 511      }
 512  
 513  }

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