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Public Member Functions
getid3_mpeg Class Reference
+ Collaboration diagram for getid3_mpeg:

Public Member Functions

 getid3_mpeg (&$fd, &$ThisFileInfo)
 MPEGsystemNonOverheadPercentage ($VideoBitrate, $AudioBitrate)
 MPEGvideoFramerateLookup ($rawframerate)
 MPEGvideoAspectRatioLookup ($rawaspectratio)
 MPEGvideoAspectRatioTextLookup ($rawaspectratio)

Detailed Description

Definition at line 28 of file module.audio-video.mpeg.php.

Member Function Documentation

getid3_mpeg::getid3_mpeg ( &  $fd,
&  $ThisFileInfo 
)

Definition at line 31 of file module.audio-video.mpeg.php.

References getid3_lib\BigEndian2Bin(), getid3_lib\BigEndian2Int(), getid3_lib\Bin2Dec(), getid3_mp3\decodeMPEGaudioHeader(), GETID3_MPEG_AUDIO_START, GETID3_MPEG_VIDEO_EXTENSION_START, GETID3_MPEG_VIDEO_SEQUENCE_HEADER, MPEGsystemNonOverheadPercentage(), MPEGvideoAspectRatioLookup(), MPEGvideoAspectRatioTextLookup(), and MPEGvideoFramerateLookup().

{
if ($ThisFileInfo['avdataend'] <= $ThisFileInfo['avdataoffset']) {
$ThisFileInfo['error'][] = '"avdataend" ('.$ThisFileInfo['avdataend'].') is unexpectedly less-than-or-equal-to "avdataoffset" ('.$ThisFileInfo['avdataoffset'].')';
return false;
}
$ThisFileInfo['fileformat'] = 'mpeg';
fseek($fd, $ThisFileInfo['avdataoffset'], SEEK_SET);
$MPEGstreamData = fread($fd, min(100000, $ThisFileInfo['avdataend'] - $ThisFileInfo['avdataoffset']));
$MPEGstreamDataLength = strlen($MPEGstreamData);
$foundVideo = true;
$VideoChunkOffset = 0;
while (substr($MPEGstreamData, $VideoChunkOffset++, 4) !== GETID3_MPEG_VIDEO_SEQUENCE_HEADER) {
if ($VideoChunkOffset >= $MPEGstreamDataLength) {
$foundVideo = false;
break;
}
}
if ($foundVideo) {
// Start code 32 bits
// horizontal frame size 12 bits
// vertical frame size 12 bits
// pixel aspect ratio 4 bits
// frame rate 4 bits
// bitrate 18 bits
// marker bit 1 bit
// VBV buffer size 10 bits
// constrained parameter flag 1 bit
// intra quant. matrix flag 1 bit
// intra quant. matrix values 512 bits (present if matrix flag == 1)
// non-intra quant. matrix flag 1 bit
// non-intra quant. matrix values 512 bits (present if matrix flag == 1)
$ThisFileInfo['video']['dataformat'] = 'mpeg';
$VideoChunkOffset += (strlen(GETID3_MPEG_VIDEO_SEQUENCE_HEADER) - 1);
$FrameSizeDWORD = getid3_lib::BigEndian2Int(substr($MPEGstreamData, $VideoChunkOffset, 3));
$VideoChunkOffset += 3;
$AspectRatioFrameRateDWORD = getid3_lib::BigEndian2Int(substr($MPEGstreamData, $VideoChunkOffset, 1));
$VideoChunkOffset += 1;
$assortedinformation = getid3_lib::BigEndian2Bin(substr($MPEGstreamData, $VideoChunkOffset, 4));
$VideoChunkOffset += 4;
$ThisFileInfo['mpeg']['video']['raw']['framesize_horizontal'] = ($FrameSizeDWORD & 0xFFF000) >> 12; // 12 bits for horizontal frame size
$ThisFileInfo['mpeg']['video']['raw']['framesize_vertical'] = ($FrameSizeDWORD & 0x000FFF); // 12 bits for vertical frame size
$ThisFileInfo['mpeg']['video']['raw']['pixel_aspect_ratio'] = ($AspectRatioFrameRateDWORD & 0xF0) >> 4;
$ThisFileInfo['mpeg']['video']['raw']['frame_rate'] = ($AspectRatioFrameRateDWORD & 0x0F);
$ThisFileInfo['mpeg']['video']['framesize_horizontal'] = $ThisFileInfo['mpeg']['video']['raw']['framesize_horizontal'];
$ThisFileInfo['mpeg']['video']['framesize_vertical'] = $ThisFileInfo['mpeg']['video']['raw']['framesize_vertical'];
$ThisFileInfo['mpeg']['video']['pixel_aspect_ratio'] = $this->MPEGvideoAspectRatioLookup($ThisFileInfo['mpeg']['video']['raw']['pixel_aspect_ratio']);
$ThisFileInfo['mpeg']['video']['pixel_aspect_ratio_text'] = $this->MPEGvideoAspectRatioTextLookup($ThisFileInfo['mpeg']['video']['raw']['pixel_aspect_ratio']);
$ThisFileInfo['mpeg']['video']['frame_rate'] = $this->MPEGvideoFramerateLookup($ThisFileInfo['mpeg']['video']['raw']['frame_rate']);
$ThisFileInfo['mpeg']['video']['raw']['bitrate'] = getid3_lib::Bin2Dec(substr($assortedinformation, 0, 18));
$ThisFileInfo['mpeg']['video']['raw']['marker_bit'] = (bool) getid3_lib::Bin2Dec(substr($assortedinformation, 18, 1));
$ThisFileInfo['mpeg']['video']['raw']['vbv_buffer_size'] = getid3_lib::Bin2Dec(substr($assortedinformation, 19, 10));
$ThisFileInfo['mpeg']['video']['raw']['constrained_param_flag'] = (bool) getid3_lib::Bin2Dec(substr($assortedinformation, 29, 1));
$ThisFileInfo['mpeg']['video']['raw']['intra_quant_flag'] = (bool) getid3_lib::Bin2Dec(substr($assortedinformation, 30, 1));
if ($ThisFileInfo['mpeg']['video']['raw']['intra_quant_flag']) {
// read 512 bits
$ThisFileInfo['mpeg']['video']['raw']['intra_quant'] = getid3_lib::BigEndian2Bin(substr($MPEGstreamData, $VideoChunkOffset, 64));
$VideoChunkOffset += 64;
$ThisFileInfo['mpeg']['video']['raw']['non_intra_quant_flag'] = (bool) getid3_lib::Bin2Dec(substr($ThisFileInfo['mpeg']['video']['raw']['intra_quant'], 511, 1));
$ThisFileInfo['mpeg']['video']['raw']['intra_quant'] = getid3_lib::Bin2Dec(substr($assortedinformation, 31, 1)).substr(getid3_lib::BigEndian2Bin(substr($MPEGstreamData, $VideoChunkOffset, 64)), 0, 511);
if ($ThisFileInfo['mpeg']['video']['raw']['non_intra_quant_flag']) {
$ThisFileInfo['mpeg']['video']['raw']['non_intra_quant'] = substr($MPEGstreamData, $VideoChunkOffset, 64);
$VideoChunkOffset += 64;
}
} else {
$ThisFileInfo['mpeg']['video']['raw']['non_intra_quant_flag'] = (bool) getid3_lib::Bin2Dec(substr($assortedinformation, 31, 1));
if ($ThisFileInfo['mpeg']['video']['raw']['non_intra_quant_flag']) {
$ThisFileInfo['mpeg']['video']['raw']['non_intra_quant'] = substr($MPEGstreamData, $VideoChunkOffset, 64);
$VideoChunkOffset += 64;
}
}
if ($ThisFileInfo['mpeg']['video']['raw']['bitrate'] == 0x3FFFF) { // 18 set bits
$ThisFileInfo['warning'][] = 'This version of getID3() ['.GETID3_VERSION.'] cannot determine average bitrate of VBR MPEG video files';
$ThisFileInfo['mpeg']['video']['bitrate_mode'] = 'vbr';
} else {
$ThisFileInfo['mpeg']['video']['bitrate'] = $ThisFileInfo['mpeg']['video']['raw']['bitrate'] * 400;
$ThisFileInfo['mpeg']['video']['bitrate_mode'] = 'cbr';
$ThisFileInfo['video']['bitrate'] = $ThisFileInfo['mpeg']['video']['bitrate'];
}
$ThisFileInfo['video']['resolution_x'] = $ThisFileInfo['mpeg']['video']['framesize_horizontal'];
$ThisFileInfo['video']['resolution_y'] = $ThisFileInfo['mpeg']['video']['framesize_vertical'];
$ThisFileInfo['video']['frame_rate'] = $ThisFileInfo['mpeg']['video']['frame_rate'];
$ThisFileInfo['video']['bitrate_mode'] = $ThisFileInfo['mpeg']['video']['bitrate_mode'];
$ThisFileInfo['video']['pixel_aspect_ratio'] = $ThisFileInfo['mpeg']['video']['pixel_aspect_ratio'];
$ThisFileInfo['video']['lossless'] = false;
$ThisFileInfo['video']['bits_per_sample'] = 24;
} else {
$ThisFileInfo['error'][] = 'Could not find start of video block in the first 100,000 bytes (or before end of file) - this might not be an MPEG-video file?';
}
//0x000001B3 begins the sequence_header of every MPEG video stream.
//But in MPEG-2, this header must immediately be followed by an
//extension_start_code (0x000001B5) with a sequence_extension ID (1).
//(This extension contains all the additional MPEG-2 stuff.)
//MPEG-1 doesn't have this extension, so that's a sure way to tell the
//difference between MPEG-1 and MPEG-2 video streams.
if (substr($MPEGstreamData, $VideoChunkOffset, 4) == GETID3_MPEG_VIDEO_EXTENSION_START) {
$ThisFileInfo['video']['codec'] = 'MPEG-2';
} else {
$ThisFileInfo['video']['codec'] = 'MPEG-1';
}
$AudioChunkOffset = 0;
while (true) {
while (substr($MPEGstreamData, $AudioChunkOffset++, 4) !== GETID3_MPEG_AUDIO_START) {
if ($AudioChunkOffset >= $MPEGstreamDataLength) {
break 2;
}
}
for ($i = 0; $i <= 7; $i++) {
// some files have the MPEG-audio header 8 bytes after the end of the $00 $00 $01 $C0 signature, some have it up to 13 bytes (or more?) after
// I have no idea why or what the difference is, so this is a stupid hack.
// If anybody has any better idea of what's going on, please let me know - info@getid3.org
$dummy = $ThisFileInfo;
if (getid3_mp3::decodeMPEGaudioHeader($fd, ($AudioChunkOffset + 3) + 8 + $i, $dummy, false)) {
$ThisFileInfo = $dummy;
$ThisFileInfo['audio']['bitrate_mode'] = 'cbr';
$ThisFileInfo['audio']['lossless'] = false;
break 2;
}
}
}
// Temporary hack to account for interleaving overhead:
if (!empty($ThisFileInfo['video']['bitrate']) && !empty($ThisFileInfo['audio']['bitrate'])) {
$ThisFileInfo['playtime_seconds'] = (($ThisFileInfo['avdataend'] - $ThisFileInfo['avdataoffset']) * 8) / ($ThisFileInfo['video']['bitrate'] + $ThisFileInfo['audio']['bitrate']);
// Interleaved MPEG audio/video files have a certain amount of overhead that varies
// by both video and audio bitrates, and not in any sensible, linear/logarithmic patter
// Use interpolated lookup tables to approximately guess how much is overhead, because
// playtime is calculated as filesize / total-bitrate
$ThisFileInfo['playtime_seconds'] *= $this->MPEGsystemNonOverheadPercentage($ThisFileInfo['video']['bitrate'], $ThisFileInfo['audio']['bitrate']);
//switch ($ThisFileInfo['video']['bitrate']) {
// case('5000000'):
// $multiplier = 0.93292642112380355828048824319889;
// break;
// case('5500000'):
// $multiplier = 0.93582895375200989965359777343219;
// break;
// case('6000000'):
// $multiplier = 0.93796247714820932532911373859139;
// break;
// case('7000000'):
// $multiplier = 0.9413264083635103463010117778776;
// break;
// default:
// $multiplier = 1;
// break;
//}
//$ThisFileInfo['playtime_seconds'] *= $multiplier;
//$ThisFileInfo['warning'][] = 'Interleaved MPEG audio/video playtime may be inaccurate. With current hack should be within a few seconds of accurate. Report to info@getid3.org if off by more than 10 seconds.';
if ($ThisFileInfo['video']['bitrate'] < 50000) {
$ThisFileInfo['warning'][] = 'Interleaved MPEG audio/video playtime may be slightly inaccurate for video bitrates below 100kbps. Except in extreme low-bitrate situations, error should be less than 1%. Report to info@getid3.org if greater than this.';
}
}
return true;
}

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getid3_mpeg::MPEGsystemNonOverheadPercentage (   $VideoBitrate,
  $AudioBitrate 
)

Definition at line 222 of file module.audio-video.mpeg.php.

Referenced by getid3_mpeg().

{
$OverheadPercentage = 0;
$AudioBitrate = max(min($AudioBitrate / 1000, 384), 32); // limit to range of 32kbps - 384kbps (should be only legal bitrates, but maybe VBR?)
$VideoBitrate = max(min($VideoBitrate / 1000, 10000), 10); // limit to range of 10kbps - 10Mbps (beyond that curves flatten anyways, no big loss)
//OMBB[audiobitrate] = array(video-10kbps, video-100kbps, video-1000kbps, video-10000kbps)
$OverheadMultiplierByBitrate[32] = array(0, 0.9676287944368530, 0.9802276264360310, 0.9844916183244460, 0.9852821845179940);
$OverheadMultiplierByBitrate[48] = array(0, 0.9779100089209830, 0.9787770035359320, 0.9846738664076130, 0.9852683013799960);
$OverheadMultiplierByBitrate[56] = array(0, 0.9731249855367600, 0.9776624308938040, 0.9832606361852130, 0.9843922606633340);
$OverheadMultiplierByBitrate[64] = array(0, 0.9755642683275760, 0.9795256705493390, 0.9836573009193170, 0.9851122539404470);
$OverheadMultiplierByBitrate[96] = array(0, 0.9788025247497290, 0.9798553314148700, 0.9822956869792560, 0.9834815119124690);
$OverheadMultiplierByBitrate[128] = array(0, 0.9816940050925480, 0.9821675936072120, 0.9829756927470870, 0.9839763420152050);
$OverheadMultiplierByBitrate[160] = array(0, 0.9825894094561180, 0.9820913399073960, 0.9823907143253970, 0.9832821783651570);
$OverheadMultiplierByBitrate[192] = array(0, 0.9832038474336260, 0.9825731694317960, 0.9821028622712400, 0.9828262076447620);
$OverheadMultiplierByBitrate[224] = array(0, 0.9836516298538770, 0.9824718601823890, 0.9818302180625380, 0.9823735101626480);
$OverheadMultiplierByBitrate[256] = array(0, 0.9845863022094920, 0.9837229411967540, 0.9824521662210830, 0.9828645172100790);
$OverheadMultiplierByBitrate[320] = array(0, 0.9849565280263180, 0.9837683142805110, 0.9822885275960400, 0.9824424382727190);
$OverheadMultiplierByBitrate[384] = array(0, 0.9856094774357600, 0.9844573394432720, 0.9825970399837330, 0.9824673808303890);
$BitrateToUseMin = 32;
$BitrateToUseMax = 32;
$previousBitrate = 32;
foreach ($OverheadMultiplierByBitrate as $key => $value) {
if ($AudioBitrate >= $previousBitrate) {
$BitrateToUseMin = $previousBitrate;
}
if ($AudioBitrate < $key) {
$BitrateToUseMax = $key;
break;
}
$previousBitrate = $key;
}
$FactorA = ($BitrateToUseMax - $AudioBitrate) / ($BitrateToUseMax - $BitrateToUseMin);
$VideoBitrateLog10 = log10($VideoBitrate);
$VideoFactorMin1 = $OverheadMultiplierByBitrate[$BitrateToUseMin][floor($VideoBitrateLog10)];
$VideoFactorMin2 = $OverheadMultiplierByBitrate[$BitrateToUseMax][floor($VideoBitrateLog10)];
$VideoFactorMax1 = $OverheadMultiplierByBitrate[$BitrateToUseMin][ceil($VideoBitrateLog10)];
$VideoFactorMax2 = $OverheadMultiplierByBitrate[$BitrateToUseMax][ceil($VideoBitrateLog10)];
$FactorV = $VideoBitrateLog10 - floor($VideoBitrateLog10);
$OverheadPercentage = $VideoFactorMin1 * $FactorA * $FactorV;
$OverheadPercentage += $VideoFactorMin2 * (1 - $FactorA) * $FactorV;
$OverheadPercentage += $VideoFactorMax1 * $FactorA * (1 - $FactorV);
$OverheadPercentage += $VideoFactorMax2 * (1 - $FactorA) * (1 - $FactorV);
return $OverheadPercentage;
}

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getid3_mpeg::MPEGvideoAspectRatioLookup (   $rawaspectratio)

Definition at line 279 of file module.audio-video.mpeg.php.

Referenced by getid3_mpeg().

{
$MPEGvideoAspectRatioLookup = array(0, 1, 0.6735, 0.7031, 0.7615, 0.8055, 0.8437, 0.8935, 0.9157, 0.9815, 1.0255, 1.0695, 1.0950, 1.1575, 1.2015, 0);
return (isset($MPEGvideoAspectRatioLookup[$rawaspectratio]) ? (float) $MPEGvideoAspectRatioLookup[$rawaspectratio] : (float) 0);
}

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getid3_mpeg::MPEGvideoAspectRatioTextLookup (   $rawaspectratio)

Definition at line 284 of file module.audio-video.mpeg.php.

Referenced by getid3_mpeg().

{
$MPEGvideoAspectRatioTextLookup = array('forbidden', 'square pixels', '0.6735', '16:9, 625 line, PAL', '0.7615', '0.8055', '16:9, 525 line, NTSC', '0.8935', '4:3, 625 line, PAL, CCIR601', '0.9815', '1.0255', '1.0695', '4:3, 525 line, NTSC, CCIR601', '1.1575', '1.2015', 'reserved');
return (isset($MPEGvideoAspectRatioTextLookup[$rawaspectratio]) ? $MPEGvideoAspectRatioTextLookup[$rawaspectratio] : '');
}

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getid3_mpeg::MPEGvideoFramerateLookup (   $rawframerate)

Definition at line 274 of file module.audio-video.mpeg.php.

Referenced by getid3_mpeg().

{
$MPEGvideoFramerateLookup = array(0, 23.976, 24, 25, 29.97, 30, 50, 59.94, 60);
return (isset($MPEGvideoFramerateLookup[$rawframerate]) ? (float) $MPEGvideoFramerateLookup[$rawframerate] : (float) 0);
}

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