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vichan/inc/lib/webm/videodata.php

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<?php
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/* This file is dedicated to the public domain; you may do as you wish with it. */
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require dirname(__FILE__) . '/matroska.php';
function matroskaSeekElement($name, $pos) {
return ebmlEncodeElement('Seek',
ebmlEncodeElement('SeekID', ebmlEncodeElementName($name))
. ebmlEncodeElement('SeekPosition', pack('N', $pos))
);
}
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// Make video from single WebM keyframe
function muxWebMFrame($videoTrack, $frame) {
$lenSeekHead = 73;
$lenCues = 24;
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// Determine version for EBML header
$version = 2;
$videoAttr = $videoTrack->get('Video');
if (isset($videoAttr)) {
if ($videoAttr->get('StereoMode') !== NULL) $version = 3;
if ($videoAttr->get('AlphaMode') !== NULL) $version = 3;
}
if ($videoTrack->get('CodecDelay') !== NULL) $version = 4;
if ($videoTrack->get('SeekPreRoll') !== NULL) $version = 4;
if ($frame->name() == 'BlockGroup' && $frame->get('DiscardPadding') !== NULL) $version = 4;
// EBML header
$ebml = ebmlEncodeElement('EBML',
ebmlEncodeElement('DocType', "webm")
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. ebmlEncodeElement('DocTypeVersion', chr($version))
. ebmlEncodeElement('DocTypeReadVersion', "\x02")
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);
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// Segment
$info = ebmlEncodeElement('Info',
ebmlEncodeElement('Duration', "\x41\x20\x00\x00")
. ebmlEncodeElement('MuxingApp', 'ccframe')
. ebmlEncodeElement('WritingApp', 'ccframe')
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);
$tracks = ebmlEncodeElement('Tracks',
ebmlEncodeElement('TrackEntry', $videoTrack->content()->readAll())
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);
$cues = ebmlEncodeElement('Cues',
ebmlEncodeElement('CuePoint',
ebmlEncodeElement('CueTime', "\x00")
. ebmlEncodeElement('CueTrackPositions',
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ebmlEncodeElement('CueTrack', pack('N', $videoTrack->get('TrackNumber')))
. ebmlEncodeElement('CueClusterPosition', pack('N', $lenSeekHead + strlen($info) + strlen($tracks) + $lenCues))
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)
)
);
if (strlen($cues) != $lenCues) throw new Exception('length of Cues element wrong');
$cluster = ebmlEncodeElement('Cluster',
ebmlEncodeElement('Timecode', "\x00")
. ebmlEncodeElement($frame->name(), $frame->content()->readAll())
. ebmlEncodeElement('Void', '')
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);
$seekHead = ebmlEncodeElement('SeekHead',
matroskaSeekElement('Info', $lenSeekHead)
. matroskaSeekElement('Tracks', $lenSeekHead + strlen($info))
. matroskaSeekElement('Cues', $lenSeekHead + strlen($info) + strlen($tracks))
. matroskaSeekElement('Cluster', $lenSeekHead + strlen($info) + strlen($tracks) + $lenCues)
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);
if (strlen($seekHead) != $lenSeekHead) throw new Exception('length of SeekHead element wrong');
$segment = ebmlEncodeElement('Segment', $seekHead . $info . $tracks . $cues . $cluster);
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return $ebml . $segment;
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}
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// Locate first WebM keyframe of track $trackNumber after timecode $skip
function firstWebMFrame($segment, $trackNumber, $skip=0) {
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foreach($segment as $x1) {
if ($x1->name() == 'Cluster') {
$cluserTimecode = $x1->Get('Timecode');
foreach($x1 as $blockGroup) {
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$blockRaw = NULL;
if ($blockGroup->name() == 'SimpleBlock') {
$blockRaw = $blockGroup->value();
} elseif ($blockGroup->name() == 'BlockGroup') {
$blockRaw = $blockGroup->get('Block');
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}
if (isset($blockRaw)) {
$block = new MatroskaBlock($blockRaw);
if ($block->trackNumber == $trackNumber && $block->keyframe) {
if (!isset($cluserTimecode) || $cluserTimecode + $block->timecode >= $skip) {
return $blockGroup;
} elseif (!isset($frame1)) {
$frame1 = $blockGroup;
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}
}
}
}
}
}
return isset($frame1) ? $frame1 : NULL;
}
function videoData($filename) {
$data = array();
// Open file
$fileHandle = fopen($filename, 'rb');
if (!$fileHandle) {
error_log('could not open file');
return $data;
}
try {
$root = readMatroska($fileHandle);
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$data['container'] = $root->get('EBML')->get('DocType');
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// Locate segment information and tracks
$segment = $root->get('Segment');
if (!isset($segment)) throw new Exception('missing Segment element');
// Get segment information
$info = $segment->get('Info');
if (isset($info)) {
$timecodeScale = $info->get('TimecodeScale');
$duration = $info->get('Duration');
if (isset($timecodeScale) && isset($duration)) {
$data['duration'] = 1e-9 * $timecodeScale * $duration;
}
}
// Locate video track
$tracks = $segment->get('Tracks');
if (!isset($tracks)) throw new Exception('missing Tracks element');
foreach($tracks as $trackEntry) {
if ($trackEntry->name() == 'TrackEntry' && $trackEntry->get('TrackType') == 1) {
$videoTrack = $trackEntry;
break;
}
}
if (!isset($videoTrack)) throw new Exception('no video track');
// Get track information
$videoAttr = $videoTrack->get('Video');
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if (!isset($videoAttr)) throw new Exception('missing video parameters');
$pixelWidth = $videoAttr->get('PixelWidth');
$pixelHeight = $videoAttr->get('PixelHeight');
if (!isset($pixelWidth) || !isset($pixelHeight)) throw new Exception('no width or height');
if ($pixelWidth == 0 || $pixelHeight == 0) throw new Exception('bad PixelWidth/PixelHeight');
$displayWidth = $videoAttr->get('DisplayWidth', $pixelWidth);
$displayHeight = $videoAttr->get('DisplayHeight', $pixelHeight);
if ($displayWidth == 0 || $displayHeight == 0) throw new Exception('bad DisplayWidth/DisplayHeight');
$data['width'] = $displayWidth;
$data['height'] = $displayHeight;
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// Extract frame to use as thumbnail
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if ($videoAttr->get('AlphaMode') != NULL) {
if (!($pixelWidth % 2 == 0 && $pixelHeight % 2 == 0 && $displayWidth % 2 == 0 && $displayHeight % 2 == 0)) {
throw new Exception('preview frame blocked due to Chromium bug');
}
}
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$trackNumber = $videoTrack->get('TrackNumber');
if (!isset($trackNumber)) throw new Exception('missing track number');
if (isset($data['duration']) && $data['duration'] >= 5) {
$skip = 1e9 / $timecodeScale;
} else {
$skip = 0;
}
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$frame = firstWebMFrame($segment, $trackNumber, $skip);
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if (!isset($frame)) throw new Exception('no keyframes');
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$data['frame'] = muxWebMFrame($videoTrack, $frame);
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} catch (Exception $e) {
error_log($e->getMessage());
}
fclose($fileHandle);
return $data;
}