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< ? php
/////////////////////////////////////////////////////////////////
/// getID3() by James Heinrich <info@getid3.org> //
// available at http://getid3.sourceforge.net //
// or http://www.getid3.org //
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// also https://github.com/JamesHeinrich/getID3 //
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/////////////////////////////////////////////////////////////////
// See readme.txt for more details //
/////////////////////////////////////////////////////////////////
// //
// module.audio.ac3.php //
// module for analyzing AC-3 (aka Dolby Digital) audio files //
// dependencies: NONE //
// ///
/////////////////////////////////////////////////////////////////
class getid3_ac3 extends getid3_handler
{
private $AC3header = array ();
private $BSIoffset = 0 ;
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const syncword = 0x0B77 ;
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public function Analyze () {
$info = & $this -> getid3 -> info ;
///AH
$info [ 'ac3' ][ 'raw' ][ 'bsi' ] = array ();
$thisfile_ac3 = & $info [ 'ac3' ];
$thisfile_ac3_raw = & $thisfile_ac3 [ 'raw' ];
$thisfile_ac3_raw_bsi = & $thisfile_ac3_raw [ 'bsi' ];
// http://www.atsc.org/standards/a_52a.pdf
$info [ 'fileformat' ] = 'ac3' ;
// An AC-3 serial coded audio bit stream is made up of a sequence of synchronization frames
// Each synchronization frame contains 6 coded audio blocks (AB), each of which represent 256
// new audio samples per channel. A synchronization information (SI) header at the beginning
// of each frame contains information needed to acquire and maintain synchronization. A
// bit stream information (BSI) header follows SI, and contains parameters describing the coded
// audio service. The coded audio blocks may be followed by an auxiliary data (Aux) field. At the
// end of each frame is an error check field that includes a CRC word for error detection. An
// additional CRC word is located in the SI header, the use of which, by a decoder, is optional.
//
// syncinfo() | bsi() | AB0 | AB1 | AB2 | AB3 | AB4 | AB5 | Aux | CRC
// syncinfo() {
// syncword 16
// crc1 16
// fscod 2
// frmsizecod 6
// } /* end of syncinfo */
$this -> fseek ( $info [ 'avdataoffset' ]);
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$tempAC3header = $this -> fread ( 100 ); // should be enough to cover all data, there are some variable-length fields...?
$this -> AC3header [ 'syncinfo' ] = getid3_lib :: BigEndian2Int ( substr ( $tempAC3header , 0 , 2 ));
$this -> AC3header [ 'bsi' ] = getid3_lib :: BigEndian2Bin ( substr ( $tempAC3header , 2 ));
$thisfile_ac3_raw_bsi [ 'bsid' ] = ( getid3_lib :: LittleEndian2Int ( substr ( $tempAC3header , 5 , 1 )) & 0xF8 ) >> 3 ; // AC3 and E-AC3 put the "bsid" version identifier in the same place, but unfortnately the 4 bytes between the syncword and the version identifier are interpreted differently, so grab it here so the following code structure can make sense
unset ( $tempAC3header );
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if ( $this -> AC3header [ 'syncinfo' ] !== self :: syncword ) {
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if ( ! $this -> isDependencyFor ( 'matroska' )) {
unset ( $info [ 'fileformat' ], $info [ 'ac3' ]);
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return $this -> error ( 'Expecting "' . dechex ( self :: syncword ) . '" at offset ' . $info [ 'avdataoffset' ] . ', found "' . dechex ( $this -> AC3header [ 'syncinfo' ]) . '"' );
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}
}
$info [ 'audio' ][ 'dataformat' ] = 'ac3' ;
$info [ 'audio' ][ 'bitrate_mode' ] = 'cbr' ;
$info [ 'audio' ][ 'lossless' ] = false ;
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if ( $thisfile_ac3_raw_bsi [ 'bsid' ] <= 8 ) {
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$thisfile_ac3_raw_bsi [ 'crc1' ] = getid3_lib :: Bin2Dec ( $this -> readHeaderBSI ( 16 ));
$thisfile_ac3_raw_bsi [ 'fscod' ] = $this -> readHeaderBSI ( 2 ); // 5.4.1.3
$thisfile_ac3_raw_bsi [ 'frmsizecod' ] = $this -> readHeaderBSI ( 6 ); // 5.4.1.4
if ( $thisfile_ac3_raw_bsi [ 'frmsizecod' ] > 37 ) { // binary: 100101 - see Table 5.18 Frame Size Code Table (1 word = 16 bits)
$this -> warning ( 'Unexpected ac3.bsi.frmsizecod value: ' . $thisfile_ac3_raw_bsi [ 'frmsizecod' ] . ', bitrate not set correctly' );
}
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$thisfile_ac3_raw_bsi [ 'bsid' ] = $this -> readHeaderBSI ( 5 ); // we already know this from pre-parsing the version identifier, but re-read it to let the bitstream flow as intended
$thisfile_ac3_raw_bsi [ 'bsmod' ] = $this -> readHeaderBSI ( 3 );
$thisfile_ac3_raw_bsi [ 'acmod' ] = $this -> readHeaderBSI ( 3 );
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if ( $thisfile_ac3_raw_bsi [ 'acmod' ] & 0x01 ) {
// If the lsb of acmod is a 1, center channel is in use and cmixlev follows in the bit stream.
$thisfile_ac3_raw_bsi [ 'cmixlev' ] = $this -> readHeaderBSI ( 2 );
$thisfile_ac3 [ 'center_mix_level' ] = self :: centerMixLevelLookup ( $thisfile_ac3_raw_bsi [ 'cmixlev' ]);
}
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if ( $thisfile_ac3_raw_bsi [ 'acmod' ] & 0x04 ) {
// If the msb of acmod is a 1, surround channels are in use and surmixlev follows in the bit stream.
$thisfile_ac3_raw_bsi [ 'surmixlev' ] = $this -> readHeaderBSI ( 2 );
$thisfile_ac3 [ 'surround_mix_level' ] = self :: surroundMixLevelLookup ( $thisfile_ac3_raw_bsi [ 'surmixlev' ]);
}
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if ( $thisfile_ac3_raw_bsi [ 'acmod' ] == 0x02 ) {
// When operating in the two channel mode, this 2-bit code indicates whether or not the program has been encoded in Dolby Surround.
$thisfile_ac3_raw_bsi [ 'dsurmod' ] = $this -> readHeaderBSI ( 2 );
$thisfile_ac3 [ 'dolby_surround_mode' ] = self :: dolbySurroundModeLookup ( $thisfile_ac3_raw_bsi [ 'dsurmod' ]);
}
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$thisfile_ac3_raw_bsi [ 'flags' ][ 'lfeon' ] = ( bool ) $this -> readHeaderBSI ( 1 );
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// This indicates how far the average dialogue level is below digital 100 percent. Valid values are 1-31.
// 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.
$thisfile_ac3_raw_bsi [ 'dialnorm' ] = $this -> readHeaderBSI ( 5 ); // 5.4.2.8 dialnorm: Dialogue Normalization, 5 Bits
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$thisfile_ac3_raw_bsi [ 'flags' ][ 'compr' ] = ( bool ) $this -> readHeaderBSI ( 1 ); // 5.4.2.9 compre: Compression Gain Word Exists, 1 Bit
if ( $thisfile_ac3_raw_bsi [ 'flags' ][ 'compr' ]) {
$thisfile_ac3_raw_bsi [ 'compr' ] = $this -> readHeaderBSI ( 8 ); // 5.4.2.10 compr: Compression Gain Word, 8 Bits
$thisfile_ac3 [ 'heavy_compression' ] = self :: heavyCompression ( $thisfile_ac3_raw_bsi [ 'compr' ]);
}
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$thisfile_ac3_raw_bsi [ 'flags' ][ 'langcod' ] = ( bool ) $this -> readHeaderBSI ( 1 ); // 5.4.2.11 langcode: Language Code Exists, 1 Bit
if ( $thisfile_ac3_raw_bsi [ 'flags' ][ 'langcod' ]) {
$thisfile_ac3_raw_bsi [ 'langcod' ] = $this -> readHeaderBSI ( 8 ); // 5.4.2.12 langcod: Language Code, 8 Bits
}
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$thisfile_ac3_raw_bsi [ 'flags' ][ 'audprodinfo' ] = ( bool ) $this -> readHeaderBSI ( 1 ); // 5.4.2.13 audprodie: Audio Production Information Exists, 1 Bit
if ( $thisfile_ac3_raw_bsi [ 'flags' ][ 'audprodinfo' ]) {
$thisfile_ac3_raw_bsi [ 'mixlevel' ] = $this -> readHeaderBSI ( 5 ); // 5.4.2.14 mixlevel: Mixing Level, 5 Bits
$thisfile_ac3_raw_bsi [ 'roomtyp' ] = $this -> readHeaderBSI ( 2 ); // 5.4.2.15 roomtyp: Room Type, 2 Bits
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$thisfile_ac3 [ 'mixing_level' ] = ( 80 + $thisfile_ac3_raw_bsi [ 'mixlevel' ]) . 'dB' ;
$thisfile_ac3 [ 'room_type' ] = self :: roomTypeLookup ( $thisfile_ac3_raw_bsi [ 'roomtyp' ]);
}
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$thisfile_ac3_raw_bsi [ 'dialnorm2' ] = $this -> readHeaderBSI ( 5 ); // 5.4.2.16 dialnorm2: Dialogue Normalization, ch2, 5 Bits
$thisfile_ac3 [ 'dialogue_normalization2' ] = '-' . $thisfile_ac3_raw_bsi [ 'dialnorm2' ] . 'dB' ; // This indicates how far the average dialogue level is below digital 100 percent. Valid values are 1-31. The value of 0 is reserved. The values of 1 to 31 are interpreted as -1 dB to -31 dB with respect to digital 100 percent.
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$thisfile_ac3_raw_bsi [ 'flags' ][ 'compr2' ] = ( bool ) $this -> readHeaderBSI ( 1 ); // 5.4.2.17 compr2e: Compression Gain Word Exists, ch2, 1 Bit
if ( $thisfile_ac3_raw_bsi [ 'flags' ][ 'compr2' ]) {
$thisfile_ac3_raw_bsi [ 'compr2' ] = $this -> readHeaderBSI ( 8 ); // 5.4.2.18 compr2: Compression Gain Word, ch2, 8 Bits
$thisfile_ac3 [ 'heavy_compression2' ] = self :: heavyCompression ( $thisfile_ac3_raw_bsi [ 'compr2' ]);
}
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$thisfile_ac3_raw_bsi [ 'flags' ][ 'langcod2' ] = ( bool ) $this -> readHeaderBSI ( 1 ); // 5.4.2.19 langcod2e: Language Code Exists, ch2, 1 Bit
if ( $thisfile_ac3_raw_bsi [ 'flags' ][ 'langcod2' ]) {
$thisfile_ac3_raw_bsi [ 'langcod2' ] = $this -> readHeaderBSI ( 8 ); // 5.4.2.20 langcod2: Language Code, ch2, 8 Bits
}
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$thisfile_ac3_raw_bsi [ 'flags' ][ 'audprodinfo2' ] = ( bool ) $this -> readHeaderBSI ( 1 ); // 5.4.2.21 audprodi2e: Audio Production Information Exists, ch2, 1 Bit
if ( $thisfile_ac3_raw_bsi [ 'flags' ][ 'audprodinfo2' ]) {
$thisfile_ac3_raw_bsi [ 'mixlevel2' ] = $this -> readHeaderBSI ( 5 ); // 5.4.2.22 mixlevel2: Mixing Level, ch2, 5 Bits
$thisfile_ac3_raw_bsi [ 'roomtyp2' ] = $this -> readHeaderBSI ( 2 ); // 5.4.2.23 roomtyp2: Room Type, ch2, 2 Bits
$thisfile_ac3 [ 'mixing_level2' ] = ( 80 + $thisfile_ac3_raw_bsi [ 'mixlevel2' ]) . 'dB' ;
$thisfile_ac3 [ 'room_type2' ] = self :: roomTypeLookup ( $thisfile_ac3_raw_bsi [ 'roomtyp2' ]);
}
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$thisfile_ac3_raw_bsi [ 'copyright' ] = ( bool ) $this -> readHeaderBSI ( 1 ); // 5.4.2.24 copyrightb: Copyright Bit, 1 Bit
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$thisfile_ac3_raw_bsi [ 'original' ] = ( bool ) $this -> readHeaderBSI ( 1 ); // 5.4.2.25 origbs: Original Bit Stream, 1 Bit
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$thisfile_ac3_raw_bsi [ 'flags' ][ 'timecod1' ] = $this -> readHeaderBSI ( 2 ); // 5.4.2.26 timecod1e, timcode2e: Time Code (first and second) Halves Exist, 2 Bits
if ( $thisfile_ac3_raw_bsi [ 'flags' ][ 'timecod1' ] & 0x01 ) {
$thisfile_ac3_raw_bsi [ 'timecod1' ] = $this -> readHeaderBSI ( 14 ); // 5.4.2.27 timecod1: Time code first half, 14 bits
$thisfile_ac3 [ 'timecode1' ] = 0 ;
$thisfile_ac3 [ 'timecode1' ] += (( $thisfile_ac3_raw_bsi [ 'timecod1' ] & 0x3E00 ) >> 9 ) * 3600 ; // The first 5 bits of this 14-bit field represent the time in hours, with valid values of 0<> 23
$thisfile_ac3 [ 'timecode1' ] += (( $thisfile_ac3_raw_bsi [ 'timecod1' ] & 0x01F8 ) >> 3 ) * 60 ; // The next 6 bits represent the time in minutes, with valid values of 0<> 59
$thisfile_ac3 [ 'timecode1' ] += (( $thisfile_ac3_raw_bsi [ 'timecod1' ] & 0x0003 ) >> 0 ) * 8 ; // The final 3 bits represents the time in 8 second increments, with valid values of 0<> 7 (representing 0, 8, 16, ... 56 seconds)
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}
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if ( $thisfile_ac3_raw_bsi [ 'flags' ][ 'timecod1' ] & 0x02 ) {
$thisfile_ac3_raw_bsi [ 'timecod2' ] = $this -> readHeaderBSI ( 14 ); // 5.4.2.28 timecod2: Time code second half, 14 bits
$thisfile_ac3 [ 'timecode2' ] = 0 ;
$thisfile_ac3 [ 'timecode2' ] += (( $thisfile_ac3_raw_bsi [ 'timecod2' ] & 0x3800 ) >> 11 ) * 1 ; // The first 3 bits of this 14-bit field represent the time in seconds, with valid values from 0<> 7 (representing 0-7 seconds)
$thisfile_ac3 [ 'timecode2' ] += (( $thisfile_ac3_raw_bsi [ 'timecod2' ] & 0x07C0 ) >> 6 ) * ( 1 / 30 ); // The next 5 bits represents the time in frames, with valid values from 0<> 29 (one frame = 1/30th of a second)
$thisfile_ac3 [ 'timecode2' ] += (( $thisfile_ac3_raw_bsi [ 'timecod2' ] & 0x003F ) >> 0 ) * (( 1 / 30 ) / 60 ); // The final 6 bits represents fractions of 1/64 of a frame, with valid values from 0<> 63
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}
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$thisfile_ac3_raw_bsi [ 'flags' ][ 'addbsi' ] = ( bool ) $this -> readHeaderBSI ( 1 );
if ( $thisfile_ac3_raw_bsi [ 'flags' ][ 'addbsi' ]) {
$thisfile_ac3_raw_bsi [ 'addbsi_length' ] = $this -> readHeaderBSI ( 6 ) + 1 ; // This 6-bit code, which exists only if addbside is a 1, indicates the length in bytes of additional bit stream information. The valid range of addbsil is 0<> 63, indicating 1<> 64 additional bytes, respectively.
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$this -> AC3header [ 'bsi' ] .= getid3_lib :: BigEndian2Bin ( $this -> fread ( $thisfile_ac3_raw_bsi [ 'addbsi_length' ]));
$thisfile_ac3_raw_bsi [ 'addbsi_data' ] = substr ( $this -> AC3header [ 'bsi' ], $this -> BSIoffset , $thisfile_ac3_raw_bsi [ 'addbsi_length' ] * 8 );
$this -> BSIoffset += $thisfile_ac3_raw_bsi [ 'addbsi_length' ] * 8 ;
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}
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} elseif ( $thisfile_ac3_raw_bsi [ 'bsid' ] <= 16 ) { // E-AC3
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$this -> error ( 'E-AC3 parsing is incomplete and experimental in this version of getID3 (' . $this -> getid3 -> version () . '). Notably the bitrate calculations are wrong -- value might (or not) be correct, but it is not calculated correctly. Email info@getid3.org if you know how to calculate EAC3 bitrate correctly.' );
$info [ 'audio' ][ 'dataformat' ] = 'eac3' ;
$thisfile_ac3_raw_bsi [ 'strmtyp' ] = $this -> readHeaderBSI ( 2 );
$thisfile_ac3_raw_bsi [ 'substreamid' ] = $this -> readHeaderBSI ( 3 );
$thisfile_ac3_raw_bsi [ 'frmsiz' ] = $this -> readHeaderBSI ( 11 );
$thisfile_ac3_raw_bsi [ 'fscod' ] = $this -> readHeaderBSI ( 2 );
if ( $thisfile_ac3_raw_bsi [ 'fscod' ] == 3 ) {
$thisfile_ac3_raw_bsi [ 'fscod2' ] = $this -> readHeaderBSI ( 2 );
$thisfile_ac3_raw_bsi [ 'numblkscod' ] = 3 ; // six blocks per syncframe
} else {
$thisfile_ac3_raw_bsi [ 'numblkscod' ] = $this -> readHeaderBSI ( 2 );
}
$thisfile_ac3 [ 'bsi' ][ 'blocks_per_sync_frame' ] = self :: blocksPerSyncFrame ( $thisfile_ac3_raw_bsi [ 'numblkscod' ]);
$thisfile_ac3_raw_bsi [ 'acmod' ] = $this -> readHeaderBSI ( 3 );
$thisfile_ac3_raw_bsi [ 'flags' ][ 'lfeon' ] = ( bool ) $this -> readHeaderBSI ( 1 );
$thisfile_ac3_raw_bsi [ 'bsid' ] = $this -> readHeaderBSI ( 5 ); // we already know this from pre-parsing the version identifier, but re-read it to let the bitstream flow as intended
$thisfile_ac3_raw_bsi [ 'dialnorm' ] = $this -> readHeaderBSI ( 5 );
$thisfile_ac3_raw_bsi [ 'flags' ][ 'compr' ] = ( bool ) $this -> readHeaderBSI ( 1 );
if ( $thisfile_ac3_raw_bsi [ 'flags' ][ 'compr' ]) {
$thisfile_ac3_raw_bsi [ 'compr' ] = $this -> readHeaderBSI ( 8 );
}
if ( $thisfile_ac3_raw_bsi [ 'acmod' ] == 0 ) { // if 1+1 mode (dual mono, so some items need a second value)
$thisfile_ac3_raw_bsi [ 'dialnorm2' ] = $this -> readHeaderBSI ( 5 );
$thisfile_ac3_raw_bsi [ 'flags' ][ 'compr2' ] = ( bool ) $this -> readHeaderBSI ( 1 );
if ( $thisfile_ac3_raw_bsi [ 'flags' ][ 'compr2' ]) {
$thisfile_ac3_raw_bsi [ 'compr2' ] = $this -> readHeaderBSI ( 8 );
}
}
if ( $thisfile_ac3_raw_bsi [ 'strmtyp' ] == 1 ) { // if dependent stream
$thisfile_ac3_raw_bsi [ 'flags' ][ 'chanmap' ] = ( bool ) $this -> readHeaderBSI ( 1 );
if ( $thisfile_ac3_raw_bsi [ 'flags' ][ 'chanmap' ]) {
$thisfile_ac3_raw_bsi [ 'chanmap' ] = $this -> readHeaderBSI ( 8 );
}
}
$thisfile_ac3_raw_bsi [ 'flags' ][ 'mixmdat' ] = ( bool ) $this -> readHeaderBSI ( 1 );
if ( $thisfile_ac3_raw_bsi [ 'flags' ][ 'mixmdat' ]) { // Mixing metadata
if ( $thisfile_ac3_raw_bsi [ 'acmod' ] > 2 ) { // if more than 2 channels
$thisfile_ac3_raw_bsi [ 'dmixmod' ] = $this -> readHeaderBSI ( 2 );
}
if (( $thisfile_ac3_raw_bsi [ 'acmod' ] & 0x01 ) && ( $thisfile_ac3_raw_bsi [ 'acmod' ] > 2 )) { // if three front channels exist
$thisfile_ac3_raw_bsi [ 'ltrtcmixlev' ] = $this -> readHeaderBSI ( 3 );
$thisfile_ac3_raw_bsi [ 'lorocmixlev' ] = $this -> readHeaderBSI ( 3 );
}
if ( $thisfile_ac3_raw_bsi [ 'acmod' ] & 0x04 ) { // if a surround channel exists
$thisfile_ac3_raw_bsi [ 'ltrtsurmixlev' ] = $this -> readHeaderBSI ( 3 );
$thisfile_ac3_raw_bsi [ 'lorosurmixlev' ] = $this -> readHeaderBSI ( 3 );
}
if ( $thisfile_ac3_raw_bsi [ 'flags' ][ 'lfeon' ]) { // if the LFE channel exists
$thisfile_ac3_raw_bsi [ 'flags' ][ 'lfemixlevcod' ] = ( bool ) $this -> readHeaderBSI ( 1 );
if ( $thisfile_ac3_raw_bsi [ 'flags' ][ 'lfemixlevcod' ]) {
$thisfile_ac3_raw_bsi [ 'lfemixlevcod' ] = $this -> readHeaderBSI ( 5 );
}
}
if ( $thisfile_ac3_raw_bsi [ 'strmtyp' ] == 0 ) { // if independent stream
$thisfile_ac3_raw_bsi [ 'flags' ][ 'pgmscl' ] = ( bool ) $this -> readHeaderBSI ( 1 );
if ( $thisfile_ac3_raw_bsi [ 'flags' ][ 'pgmscl' ]) {
$thisfile_ac3_raw_bsi [ 'pgmscl' ] = $this -> readHeaderBSI ( 6 );
}
if ( $thisfile_ac3_raw_bsi [ 'acmod' ] == 0 ) { // if 1+1 mode (dual mono, so some items need a second value)
$thisfile_ac3_raw_bsi [ 'flags' ][ 'pgmscl2' ] = ( bool ) $this -> readHeaderBSI ( 1 );
if ( $thisfile_ac3_raw_bsi [ 'flags' ][ 'pgmscl2' ]) {
$thisfile_ac3_raw_bsi [ 'pgmscl2' ] = $this -> readHeaderBSI ( 6 );
}
}
$thisfile_ac3_raw_bsi [ 'flags' ][ 'extpgmscl' ] = ( bool ) $this -> readHeaderBSI ( 1 );
if ( $thisfile_ac3_raw_bsi [ 'flags' ][ 'extpgmscl' ]) {
$thisfile_ac3_raw_bsi [ 'extpgmscl' ] = $this -> readHeaderBSI ( 6 );
}
$thisfile_ac3_raw_bsi [ 'mixdef' ] = $this -> readHeaderBSI ( 2 );
if ( $thisfile_ac3_raw_bsi [ 'mixdef' ] == 1 ) { // mixing option 2
$thisfile_ac3_raw_bsi [ 'premixcmpsel' ] = ( bool ) $this -> readHeaderBSI ( 1 );
$thisfile_ac3_raw_bsi [ 'drcsrc' ] = ( bool ) $this -> readHeaderBSI ( 1 );
$thisfile_ac3_raw_bsi [ 'premixcmpscl' ] = $this -> readHeaderBSI ( 3 );
} elseif ( $thisfile_ac3_raw_bsi [ 'mixdef' ] == 2 ) { // mixing option 3
$thisfile_ac3_raw_bsi [ 'mixdata' ] = $this -> readHeaderBSI ( 12 );
} elseif ( $thisfile_ac3_raw_bsi [ 'mixdef' ] == 3 ) { // mixing option 4
$mixdefbitsread = 0 ;
$thisfile_ac3_raw_bsi [ 'mixdeflen' ] = $this -> readHeaderBSI ( 5 ); $mixdefbitsread += 5 ;
$thisfile_ac3_raw_bsi [ 'flags' ][ 'mixdata2' ] = ( bool ) $this -> readHeaderBSI ( 1 ); $mixdefbitsread += 1 ;
if ( $thisfile_ac3_raw_bsi [ 'flags' ][ 'mixdata2' ]) {
$thisfile_ac3_raw_bsi [ 'premixcmpsel' ] = ( bool ) $this -> readHeaderBSI ( 1 ); $mixdefbitsread += 1 ;
$thisfile_ac3_raw_bsi [ 'drcsrc' ] = ( bool ) $this -> readHeaderBSI ( 1 ); $mixdefbitsread += 1 ;
$thisfile_ac3_raw_bsi [ 'premixcmpscl' ] = $this -> readHeaderBSI ( 3 ); $mixdefbitsread += 3 ;
$thisfile_ac3_raw_bsi [ 'flags' ][ 'extpgmlscl' ] = ( bool ) $this -> readHeaderBSI ( 1 ); $mixdefbitsread += 1 ;
if ( $thisfile_ac3_raw_bsi [ 'flags' ][ 'extpgmlscl' ]) {
$thisfile_ac3_raw_bsi [ 'extpgmlscl' ] = $this -> readHeaderBSI ( 4 ); $mixdefbitsread += 4 ;
}
$thisfile_ac3_raw_bsi [ 'flags' ][ 'extpgmcscl' ] = ( bool ) $this -> readHeaderBSI ( 1 ); $mixdefbitsread += 1 ;
if ( $thisfile_ac3_raw_bsi [ 'flags' ][ 'extpgmcscl' ]) {
$thisfile_ac3_raw_bsi [ 'extpgmcscl' ] = $this -> readHeaderBSI ( 4 ); $mixdefbitsread += 4 ;
}
$thisfile_ac3_raw_bsi [ 'flags' ][ 'extpgmrscl' ] = ( bool ) $this -> readHeaderBSI ( 1 ); $mixdefbitsread += 1 ;
if ( $thisfile_ac3_raw_bsi [ 'flags' ][ 'extpgmrscl' ]) {
$thisfile_ac3_raw_bsi [ 'extpgmrscl' ] = $this -> readHeaderBSI ( 4 );
}
$thisfile_ac3_raw_bsi [ 'flags' ][ 'extpgmlsscl' ] = ( bool ) $this -> readHeaderBSI ( 1 ); $mixdefbitsread += 1 ;
if ( $thisfile_ac3_raw_bsi [ 'flags' ][ 'extpgmlsscl' ]) {
$thisfile_ac3_raw_bsi [ 'extpgmlsscl' ] = $this -> readHeaderBSI ( 4 ); $mixdefbitsread += 4 ;
}
$thisfile_ac3_raw_bsi [ 'flags' ][ 'extpgmrsscl' ] = ( bool ) $this -> readHeaderBSI ( 1 ); $mixdefbitsread += 1 ;
if ( $thisfile_ac3_raw_bsi [ 'flags' ][ 'extpgmrsscl' ]) {
$thisfile_ac3_raw_bsi [ 'extpgmrsscl' ] = $this -> readHeaderBSI ( 4 ); $mixdefbitsread += 4 ;
}
$thisfile_ac3_raw_bsi [ 'flags' ][ 'extpgmlfescl' ] = ( bool ) $this -> readHeaderBSI ( 1 ); $mixdefbitsread += 1 ;
if ( $thisfile_ac3_raw_bsi [ 'flags' ][ 'extpgmlfescl' ]) {
$thisfile_ac3_raw_bsi [ 'extpgmlfescl' ] = $this -> readHeaderBSI ( 4 ); $mixdefbitsread += 4 ;
}
$thisfile_ac3_raw_bsi [ 'flags' ][ 'dmixscl' ] = ( bool ) $this -> readHeaderBSI ( 1 ); $mixdefbitsread += 1 ;
if ( $thisfile_ac3_raw_bsi [ 'flags' ][ 'dmixscl' ]) {
$thisfile_ac3_raw_bsi [ 'dmixscl' ] = $this -> readHeaderBSI ( 4 ); $mixdefbitsread += 4 ;
}
$thisfile_ac3_raw_bsi [ 'flags' ][ 'addch' ] = ( bool ) $this -> readHeaderBSI ( 1 ); $mixdefbitsread += 1 ;
if ( $thisfile_ac3_raw_bsi [ 'flags' ][ 'addch' ]) {
$thisfile_ac3_raw_bsi [ 'flags' ][ 'extpgmaux1scl' ] = ( bool ) $this -> readHeaderBSI ( 1 ); $mixdefbitsread += 1 ;
if ( $thisfile_ac3_raw_bsi [ 'flags' ][ 'extpgmaux1scl' ]) {
$thisfile_ac3_raw_bsi [ 'extpgmaux1scl' ] = $this -> readHeaderBSI ( 4 ); $mixdefbitsread += 4 ;
}
$thisfile_ac3_raw_bsi [ 'flags' ][ 'extpgmaux2scl' ] = ( bool ) $this -> readHeaderBSI ( 1 ); $mixdefbitsread += 1 ;
if ( $thisfile_ac3_raw_bsi [ 'flags' ][ 'extpgmaux2scl' ]) {
$thisfile_ac3_raw_bsi [ 'extpgmaux2scl' ] = $this -> readHeaderBSI ( 4 ); $mixdefbitsread += 4 ;
}
}
}
$thisfile_ac3_raw_bsi [ 'flags' ][ 'mixdata3' ] = ( bool ) $this -> readHeaderBSI ( 1 ); $mixdefbitsread += 1 ;
if ( $thisfile_ac3_raw_bsi [ 'flags' ][ 'mixdata3' ]) {
$thisfile_ac3_raw_bsi [ 'spchdat' ] = $this -> readHeaderBSI ( 5 ); $mixdefbitsread += 5 ;
$thisfile_ac3_raw_bsi [ 'flags' ][ 'addspchdat' ] = ( bool ) $this -> readHeaderBSI ( 1 ); $mixdefbitsread += 1 ;
if ( $thisfile_ac3_raw_bsi [ 'flags' ][ 'addspchdat' ]) {
$thisfile_ac3_raw_bsi [ 'spchdat1' ] = $this -> readHeaderBSI ( 5 ); $mixdefbitsread += 5 ;
$thisfile_ac3_raw_bsi [ 'spchan1att' ] = $this -> readHeaderBSI ( 2 ); $mixdefbitsread += 2 ;
$thisfile_ac3_raw_bsi [ 'flags' ][ 'addspchdat1' ] = ( bool ) $this -> readHeaderBSI ( 1 ); $mixdefbitsread += 1 ;
if ( $thisfile_ac3_raw_bsi [ 'flags' ][ 'addspchdat1' ]) {
$thisfile_ac3_raw_bsi [ 'spchdat2' ] = $this -> readHeaderBSI ( 5 ); $mixdefbitsread += 5 ;
$thisfile_ac3_raw_bsi [ 'spchan2att' ] = $this -> readHeaderBSI ( 3 ); $mixdefbitsread += 3 ;
}
}
}
$mixdata_bits = ( 8 * ( $thisfile_ac3_raw_bsi [ 'mixdeflen' ] + 2 )) - $mixdefbitsread ;
$mixdata_fill = (( $mixdata_bits % 8 ) ? 8 - ( $mixdata_bits % 8 ) : 0 );
$thisfile_ac3_raw_bsi [ 'mixdata' ] = $this -> readHeaderBSI ( $mixdata_bits );
$thisfile_ac3_raw_bsi [ 'mixdatafill' ] = $this -> readHeaderBSI ( $mixdata_fill );
unset ( $mixdefbitsread , $mixdata_bits , $mixdata_fill );
}
if ( $thisfile_ac3_raw_bsi [ 'acmod' ] < 2 ) { // if mono or dual mono source
$thisfile_ac3_raw_bsi [ 'flags' ][ 'paninfo' ] = ( bool ) $this -> readHeaderBSI ( 1 );
if ( $thisfile_ac3_raw_bsi [ 'flags' ][ 'paninfo' ]) {
$thisfile_ac3_raw_bsi [ 'panmean' ] = $this -> readHeaderBSI ( 8 );
$thisfile_ac3_raw_bsi [ 'paninfo' ] = $this -> readHeaderBSI ( 6 );
}
if ( $thisfile_ac3_raw_bsi [ 'acmod' ] == 0 ) { // if 1+1 mode (dual mono, so some items need a second value)
$thisfile_ac3_raw_bsi [ 'flags' ][ 'paninfo2' ] = ( bool ) $this -> readHeaderBSI ( 1 );
if ( $thisfile_ac3_raw_bsi [ 'flags' ][ 'paninfo2' ]) {
$thisfile_ac3_raw_bsi [ 'panmean2' ] = $this -> readHeaderBSI ( 8 );
$thisfile_ac3_raw_bsi [ 'paninfo2' ] = $this -> readHeaderBSI ( 6 );
}
}
}
$thisfile_ac3_raw_bsi [ 'flags' ][ 'frmmixcfginfo' ] = ( bool ) $this -> readHeaderBSI ( 1 );
if ( $thisfile_ac3_raw_bsi [ 'flags' ][ 'frmmixcfginfo' ]) { // mixing configuration information
if ( $thisfile_ac3_raw_bsi [ 'numblkscod' ] == 0 ) {
$thisfile_ac3_raw_bsi [ 'blkmixcfginfo' ][ 0 ] = $this -> readHeaderBSI ( 5 );
} else {
for ( $blk = 0 ; $blk < $thisfile_ac3_raw_bsi [ 'numblkscod' ]; $blk ++ ) {
$thisfile_ac3_raw_bsi [ 'flags' ][ 'blkmixcfginfo' . $blk ] = ( bool ) $this -> readHeaderBSI ( 1 );
if ( $thisfile_ac3_raw_bsi [ 'flags' ][ 'blkmixcfginfo' . $blk ]) { // mixing configuration information
$thisfile_ac3_raw_bsi [ 'blkmixcfginfo' ][ $blk ] = $this -> readHeaderBSI ( 5 );
}
}
}
}
}
}
$thisfile_ac3_raw_bsi [ 'flags' ][ 'infomdat' ] = ( bool ) $this -> readHeaderBSI ( 1 );
if ( $thisfile_ac3_raw_bsi [ 'flags' ][ 'infomdat' ]) { // Informational metadata
$thisfile_ac3_raw_bsi [ 'bsmod' ] = $this -> readHeaderBSI ( 3 );
$thisfile_ac3_raw_bsi [ 'flags' ][ 'copyrightb' ] = ( bool ) $this -> readHeaderBSI ( 1 );
$thisfile_ac3_raw_bsi [ 'flags' ][ 'origbs' ] = ( bool ) $this -> readHeaderBSI ( 1 );
if ( $thisfile_ac3_raw_bsi [ 'acmod' ] == 2 ) { // if in 2/0 mode
$thisfile_ac3_raw_bsi [ 'dsurmod' ] = $this -> readHeaderBSI ( 2 );
$thisfile_ac3_raw_bsi [ 'dheadphonmod' ] = $this -> readHeaderBSI ( 2 );
}
if ( $thisfile_ac3_raw_bsi [ 'acmod' ] >= 6 ) { // if both surround channels exist
$thisfile_ac3_raw_bsi [ 'dsurexmod' ] = $this -> readHeaderBSI ( 2 );
}
$thisfile_ac3_raw_bsi [ 'flags' ][ 'audprodi' ] = ( bool ) $this -> readHeaderBSI ( 1 );
if ( $thisfile_ac3_raw_bsi [ 'flags' ][ 'audprodi' ]) {
$thisfile_ac3_raw_bsi [ 'mixlevel' ] = $this -> readHeaderBSI ( 5 );
$thisfile_ac3_raw_bsi [ 'roomtyp' ] = $this -> readHeaderBSI ( 2 );
$thisfile_ac3_raw_bsi [ 'flags' ][ 'adconvtyp' ] = ( bool ) $this -> readHeaderBSI ( 1 );
}
if ( $thisfile_ac3_raw_bsi [ 'acmod' ] == 0 ) { // if 1+1 mode (dual mono, so some items need a second value)
$thisfile_ac3_raw_bsi [ 'flags' ][ 'audprodi2' ] = ( bool ) $this -> readHeaderBSI ( 1 );
if ( $thisfile_ac3_raw_bsi [ 'flags' ][ 'audprodi2' ]) {
$thisfile_ac3_raw_bsi [ 'mixlevel2' ] = $this -> readHeaderBSI ( 5 );
$thisfile_ac3_raw_bsi [ 'roomtyp2' ] = $this -> readHeaderBSI ( 2 );
$thisfile_ac3_raw_bsi [ 'flags' ][ 'adconvtyp2' ] = ( bool ) $this -> readHeaderBSI ( 1 );
}
}
if ( $thisfile_ac3_raw_bsi [ 'fscod' ] < 3 ) { // if not half sample rate
$thisfile_ac3_raw_bsi [ 'flags' ][ 'sourcefscod' ] = ( bool ) $this -> readHeaderBSI ( 1 );
}
}
if (( $thisfile_ac3_raw_bsi [ 'strmtyp' ] == 0 ) && ( $thisfile_ac3_raw_bsi [ 'numblkscod' ] != 3 )) { // if both surround channels exist
$thisfile_ac3_raw_bsi [ 'flags' ][ 'convsync' ] = ( bool ) $this -> readHeaderBSI ( 1 );
}
if ( $thisfile_ac3_raw_bsi [ 'strmtyp' ] == 2 ) { // if bit stream converted from AC-3
if ( $thisfile_ac3_raw_bsi [ 'numblkscod' ] != 3 ) { // 6 blocks per syncframe
$thisfile_ac3_raw_bsi [ 'flags' ][ 'blkid' ] = 1 ;
} else {
$thisfile_ac3_raw_bsi [ 'flags' ][ 'blkid' ] = ( bool ) $this -> readHeaderBSI ( 1 );
}
if ( $thisfile_ac3_raw_bsi [ 'flags' ][ 'blkid' ]) {
$thisfile_ac3_raw_bsi [ 'frmsizecod' ] = $this -> readHeaderBSI ( 6 );
}
}
$thisfile_ac3_raw_bsi [ 'flags' ][ 'addbsi' ] = ( bool ) $this -> readHeaderBSI ( 1 );
if ( $thisfile_ac3_raw_bsi [ 'flags' ][ 'addbsi' ]) {
$thisfile_ac3_raw_bsi [ 'addbsil' ] = $this -> readHeaderBSI ( 6 );
$thisfile_ac3_raw_bsi [ 'addbsi' ] = $this -> readHeaderBSI (( $thisfile_ac3_raw_bsi [ 'addbsil' ] + 1 ) * 8 );
}
} else {
$this -> error ( 'Bit stream identification is version ' . $thisfile_ac3_raw_bsi [ 'bsid' ] . ', but getID3() only understands up to version 16. Please submit a support ticket with a sample file.' );
unset ( $info [ 'ac3' ]);
return false ;
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}
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if ( isset ( $thisfile_ac3_raw_bsi [ 'fscod2' ])) {
$thisfile_ac3 [ 'sample_rate' ] = self :: sampleRateCodeLookup2 ( $thisfile_ac3_raw_bsi [ 'fscod2' ]);
} else {
$thisfile_ac3 [ 'sample_rate' ] = self :: sampleRateCodeLookup ( $thisfile_ac3_raw_bsi [ 'fscod' ]);
}
if ( $thisfile_ac3_raw_bsi [ 'fscod' ] <= 3 ) {
$info [ 'audio' ][ 'sample_rate' ] = $thisfile_ac3 [ 'sample_rate' ];
} else {
$this -> warning ( 'Unexpected ac3.bsi.fscod value: ' . $thisfile_ac3_raw_bsi [ 'fscod' ]);
}
if ( isset ( $thisfile_ac3_raw_bsi [ 'frmsizecod' ])) {
$thisfile_ac3 [ 'frame_length' ] = self :: frameSizeLookup ( $thisfile_ac3_raw_bsi [ 'frmsizecod' ], $thisfile_ac3_raw_bsi [ 'fscod' ]);
$thisfile_ac3 [ 'bitrate' ] = self :: bitrateLookup ( $thisfile_ac3_raw_bsi [ 'frmsizecod' ]);
} elseif ( ! empty ( $thisfile_ac3_raw_bsi [ 'frmsiz' ])) {
// this isn't right, but it's (usually) close, roughly 5% less than it should be.
// but WHERE is the actual bitrate value stored in EAC3?? email info@getid3.org if you know!
$thisfile_ac3 [ 'bitrate' ] = ( $thisfile_ac3_raw_bsi [ 'frmsiz' ] + 1 ) * 16 * 30 ; // The frmsiz field shall contain a value one less than the overall size of the coded syncframe in 16-bit words. That is, this field may assume a value ranging from 0 to 2047, and these values correspond to syncframe sizes ranging from 1 to 2048.
// kludge-fix to make it approximately the expected value, still not "right":
$thisfile_ac3 [ 'bitrate' ] = round (( $thisfile_ac3 [ 'bitrate' ] * 1.05 ) / 16000 ) * 16000 ;
}
$info [ 'audio' ][ 'bitrate' ] = $thisfile_ac3 [ 'bitrate' ];
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$thisfile_ac3 [ 'service_type' ] = self :: serviceTypeLookup ( $thisfile_ac3_raw_bsi [ 'bsmod' ], $thisfile_ac3_raw_bsi [ 'acmod' ]);
$ac3_coding_mode = self :: audioCodingModeLookup ( $thisfile_ac3_raw_bsi [ 'acmod' ]);
foreach ( $ac3_coding_mode as $key => $value ) {
$thisfile_ac3 [ $key ] = $value ;
}
switch ( $thisfile_ac3_raw_bsi [ 'acmod' ]) {
case 0 :
case 1 :
$info [ 'audio' ][ 'channelmode' ] = 'mono' ;
break ;
case 3 :
case 4 :
$info [ 'audio' ][ 'channelmode' ] = 'stereo' ;
break ;
default :
$info [ 'audio' ][ 'channelmode' ] = 'surround' ;
break ;
}
$info [ 'audio' ][ 'channels' ] = $thisfile_ac3 [ 'num_channels' ];
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$thisfile_ac3 [ 'lfe_enabled' ] = $thisfile_ac3_raw_bsi [ 'flags' ][ 'lfeon' ];
if ( $thisfile_ac3_raw_bsi [ 'flags' ][ 'lfeon' ]) {
$info [ 'audio' ][ 'channels' ] .= '.1' ;
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}
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$thisfile_ac3 [ 'channels_enabled' ] = self :: channelsEnabledLookup ( $thisfile_ac3_raw_bsi [ 'acmod' ], $thisfile_ac3_raw_bsi [ 'flags' ][ 'lfeon' ]);
$thisfile_ac3 [ 'dialogue_normalization' ] = '-' . $thisfile_ac3_raw_bsi [ 'dialnorm' ] . 'dB' ;
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return true ;
}
private function readHeaderBSI ( $length ) {
$data = substr ( $this -> AC3header [ 'bsi' ], $this -> BSIoffset , $length );
$this -> BSIoffset += $length ;
return bindec ( $data );
}
public static function sampleRateCodeLookup ( $fscod ) {
static $sampleRateCodeLookup = array (
0 => 48000 ,
1 => 44100 ,
2 => 32000 ,
3 => 'reserved' // If the reserved code is indicated, the decoder should not attempt to decode audio and should mute.
);
return ( isset ( $sampleRateCodeLookup [ $fscod ]) ? $sampleRateCodeLookup [ $fscod ] : false );
}
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public static function sampleRateCodeLookup2 ( $fscod2 ) {
static $sampleRateCodeLookup2 = array (
0 => 24000 ,
1 => 22050 ,
2 => 16000 ,
3 => 'reserved' // If the reserved code is indicated, the decoder should not attempt to decode audio and should mute.
);
return ( isset ( $sampleRateCodeLookup2 [ $fscod2 ]) ? $sampleRateCodeLookup2 [ $fscod2 ] : false );
}
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public static function serviceTypeLookup ( $bsmod , $acmod ) {
static $serviceTypeLookup = array ();
if ( empty ( $serviceTypeLookup )) {
for ( $i = 0 ; $i <= 7 ; $i ++ ) {
$serviceTypeLookup [ 0 ][ $i ] = 'main audio service: complete main (CM)' ;
$serviceTypeLookup [ 1 ][ $i ] = 'main audio service: music and effects (ME)' ;
$serviceTypeLookup [ 2 ][ $i ] = 'associated service: visually impaired (VI)' ;
$serviceTypeLookup [ 3 ][ $i ] = 'associated service: hearing impaired (HI)' ;
$serviceTypeLookup [ 4 ][ $i ] = 'associated service: dialogue (D)' ;
$serviceTypeLookup [ 5 ][ $i ] = 'associated service: commentary (C)' ;
$serviceTypeLookup [ 6 ][ $i ] = 'associated service: emergency (E)' ;
}
$serviceTypeLookup [ 7 ][ 1 ] = 'associated service: voice over (VO)' ;
for ( $i = 2 ; $i <= 7 ; $i ++ ) {
$serviceTypeLookup [ 7 ][ $i ] = 'main audio service: karaoke' ;
}
}
return ( isset ( $serviceTypeLookup [ $bsmod ][ $acmod ]) ? $serviceTypeLookup [ $bsmod ][ $acmod ] : false );
}
public static function audioCodingModeLookup ( $acmod ) {
// array(channel configuration, # channels (not incl LFE), channel order)
static $audioCodingModeLookup = array (
0 => array ( 'channel_config' => '1+1' , 'num_channels' => 2 , 'channel_order' => 'Ch1,Ch2' ),
1 => array ( 'channel_config' => '1/0' , 'num_channels' => 1 , 'channel_order' => 'C' ),
2 => array ( 'channel_config' => '2/0' , 'num_channels' => 2 , 'channel_order' => 'L,R' ),
3 => array ( 'channel_config' => '3/0' , 'num_channels' => 3 , 'channel_order' => 'L,C,R' ),
4 => array ( 'channel_config' => '2/1' , 'num_channels' => 3 , 'channel_order' => 'L,R,S' ),
5 => array ( 'channel_config' => '3/1' , 'num_channels' => 4 , 'channel_order' => 'L,C,R,S' ),
6 => array ( 'channel_config' => '2/2' , 'num_channels' => 4 , 'channel_order' => 'L,R,SL,SR' ),
7 => array ( 'channel_config' => '3/2' , 'num_channels' => 5 , 'channel_order' => 'L,C,R,SL,SR' ),
);
return ( isset ( $audioCodingModeLookup [ $acmod ]) ? $audioCodingModeLookup [ $acmod ] : false );
}
public static function centerMixLevelLookup ( $cmixlev ) {
static $centerMixLevelLookup ;
if ( empty ( $centerMixLevelLookup )) {
$centerMixLevelLookup = array (
0 => pow ( 2 , - 3.0 / 6 ), // 0.707 (-3.0 dB)
1 => pow ( 2 , - 4.5 / 6 ), // 0.595 (-4.5 dB)
2 => pow ( 2 , - 6.0 / 6 ), // 0.500 (-6.0 dB)
3 => 'reserved'
);
}
return ( isset ( $centerMixLevelLookup [ $cmixlev ]) ? $centerMixLevelLookup [ $cmixlev ] : false );
}
public static function surroundMixLevelLookup ( $surmixlev ) {
static $surroundMixLevelLookup ;
if ( empty ( $surroundMixLevelLookup )) {
$surroundMixLevelLookup = array (
0 => pow ( 2 , - 3.0 / 6 ),
1 => pow ( 2 , - 6.0 / 6 ),
2 => 0 ,
3 => 'reserved'
);
}
return ( isset ( $surroundMixLevelLookup [ $surmixlev ]) ? $surroundMixLevelLookup [ $surmixlev ] : false );
}
public static function dolbySurroundModeLookup ( $dsurmod ) {
static $dolbySurroundModeLookup = array (
0 => 'not indicated' ,
1 => 'Not Dolby Surround encoded' ,
2 => 'Dolby Surround encoded' ,
3 => 'reserved'
);
return ( isset ( $dolbySurroundModeLookup [ $dsurmod ]) ? $dolbySurroundModeLookup [ $dsurmod ] : false );
}
public static function channelsEnabledLookup ( $acmod , $lfeon ) {
$lookup = array (
'ch1' => ( bool ) ( $acmod == 0 ),
'ch2' => ( bool ) ( $acmod == 0 ),
'left' => ( bool ) ( $acmod > 1 ),
'right' => ( bool ) ( $acmod > 1 ),
'center' => ( bool ) ( $acmod & 0x01 ),
'surround_mono' => false ,
'surround_left' => false ,
'surround_right' => false ,
'lfe' => $lfeon );
switch ( $acmod ) {
case 4 :
case 5 :
$lookup [ 'surround_mono' ] = true ;
break ;
case 6 :
case 7 :
$lookup [ 'surround_left' ] = true ;
$lookup [ 'surround_right' ] = true ;
break ;
}
return $lookup ;
}
public static function heavyCompression ( $compre ) {
// The first four bits indicate gain changes in 6.02dB increments which can be
// implemented with an arithmetic shift operation. The following four bits
// indicate linear gain changes, and require a 5-bit multiply.
// We will represent the two 4-bit fields of compr as follows:
// X0 X1 X2 X3 . Y4 Y5 Y6 Y7
// The meaning of the X values is most simply described by considering X to represent a 4-bit
// signed integer with values from -8 to +7. The gain indicated by X is then (X + 1) * 6.02 dB. The
// following table shows this in detail.
// Meaning of 4 msb of compr
// 7 +48.16 dB
// 6 +42.14 dB
// 5 +36.12 dB
// 4 +30.10 dB
// 3 +24.08 dB
// 2 +18.06 dB
// 1 +12.04 dB
// 0 +6.02 dB
// -1 0 dB
// -2 -6.02 dB
// -3 -12.04 dB
// -4 -18.06 dB
// -5 -24.08 dB
// -6 -30.10 dB
// -7 -36.12 dB
// -8 -42.14 dB
$fourbit = str_pad ( decbin (( $compre & 0xF0 ) >> 4 ), 4 , '0' , STR_PAD_LEFT );
if ( $fourbit { 0 } == '1' ) {
$log_gain = - 8 + bindec ( substr ( $fourbit , 1 ));
} else {
$log_gain = bindec ( substr ( $fourbit , 1 ));
}
$log_gain = ( $log_gain + 1 ) * getid3_lib :: RGADamplitude2dB ( 2 );
// The value of Y is a linear representation of a gain change of up to -6 dB. Y is considered to
// be an unsigned fractional integer, with a leading value of 1, or: 0.1 Y4 Y5 Y6 Y7 (base 2). Y can
// represent values between 0.111112 (or 31/32) and 0.100002 (or 1/2). Thus, Y can represent gain
// changes from -0.28 dB to -6.02 dB.
$lin_gain = ( 16 + ( $compre & 0x0F )) / 32 ;
// The combination of X and Y values allows compr to indicate gain changes from
// 48.16 - 0.28 = +47.89 dB, to
// -42.14 - 6.02 = -48.16 dB.
return $log_gain - $lin_gain ;
}
public static function roomTypeLookup ( $roomtyp ) {
static $roomTypeLookup = array (
0 => 'not indicated' ,
1 => 'large room, X curve monitor' ,
2 => 'small room, flat monitor' ,
3 => 'reserved'
);
return ( isset ( $roomTypeLookup [ $roomtyp ]) ? $roomTypeLookup [ $roomtyp ] : false );
}
public static function frameSizeLookup ( $frmsizecod , $fscod ) {
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// LSB is whether padding is used or not
$padding = ( bool ) ( $frmsizecod & 0x01 );
$framesizeid = ( $frmsizecod & 0x3E ) >> 1 ;
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static $frameSizeLookup = array ();
if ( empty ( $frameSizeLookup )) {
$frameSizeLookup = array (
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0 => array ( 128 , 138 , 192 ), // 32 kbps
1 => array ( 160 , 174 , 240 ), // 40 kbps
2 => array ( 192 , 208 , 288 ), // 48 kbps
3 => array ( 224 , 242 , 336 ), // 56 kbps
4 => array ( 256 , 278 , 384 ), // 64 kbps
5 => array ( 320 , 348 , 480 ), // 80 kbps
6 => array ( 384 , 416 , 576 ), // 96 kbps
7 => array ( 448 , 486 , 672 ), // 112 kbps
8 => array ( 512 , 556 , 768 ), // 128 kbps
9 => array ( 640 , 696 , 960 ), // 160 kbps
10 => array ( 768 , 834 , 1152 ), // 192 kbps
11 => array ( 896 , 974 , 1344 ), // 224 kbps
12 => array ( 1024 , 1114 , 1536 ), // 256 kbps
13 => array ( 1280 , 1392 , 1920 ), // 320 kbps
14 => array ( 1536 , 1670 , 2304 ), // 384 kbps
15 => array ( 1792 , 1950 , 2688 ), // 448 kbps
16 => array ( 2048 , 2228 , 3072 ), // 512 kbps
17 => array ( 2304 , 2506 , 3456 ), // 576 kbps
18 => array ( 2560 , 2786 , 3840 ) // 640 kbps
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);
}
if (( $fscod == 1 ) && $padding ) {
// frame lengths are padded by 1 word (16 bits) at 44100
$frameSizeLookup [ $frmsizecod ] += 2 ;
}
return ( isset ( $frameSizeLookup [ $framesizeid ][ $fscod ]) ? $frameSizeLookup [ $framesizeid ][ $fscod ] : false );
}
public static function bitrateLookup ( $frmsizecod ) {
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// LSB is whether padding is used or not
$padding = ( bool ) ( $frmsizecod & 0x01 );
$framesizeid = ( $frmsizecod & 0x3E ) >> 1 ;
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static $bitrateLookup = array (
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0 => 32000 ,
1 => 40000 ,
2 => 48000 ,
3 => 56000 ,
4 => 64000 ,
5 => 80000 ,
6 => 96000 ,
7 => 112000 ,
8 => 128000 ,
9 => 160000 ,
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10 => 192000 ,
11 => 224000 ,
12 => 256000 ,
13 => 320000 ,
14 => 384000 ,
15 => 448000 ,
16 => 512000 ,
17 => 576000 ,
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18 => 640000 ,
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);
return ( isset ( $bitrateLookup [ $framesizeid ]) ? $bitrateLookup [ $framesizeid ] : false );
}
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public static function blocksPerSyncFrame ( $numblkscod ) {
static $blocksPerSyncFrameLookup = array (
0 => 1 ,
1 => 2 ,
2 => 3 ,
3 => 6 ,
);
return ( isset ( $blocksPerSyncFrameLookup [ $numblkscod ]) ? $blocksPerSyncFrameLookup [ $numblkscod ] : false );
}
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}
