function _decodeCommentsHeader()
{
fseek($this->_filePointer, $this->_streamData['pages'][1]['body_offset'], SEEK_SET);
$blockHeader = File_Ogg::_readBigEndian($this->_filePointer, array('last_block' => 1, 'block_type' => 7, 'length' => 24));
if ($blockHeader['block_type'] != 4) {
throw new PEAR_Exception("Stream Undecodable", OGG_ERROR_UNDECODABLE);
}
$this->_decodeBareCommentsHeader();
}
/**
* Parse the identification header in a Theora stream.
* @access private
*/
function _decodeIdentificationHeader()
{
$this->_decodeCommonHeader(OGG_THEORA_IDENTIFICATION_HEADER, OGG_THEORA_IDENTIFICATION_PAGE_OFFSET);
$h = File_Ogg::_readBigEndian($this->_filePointer, array('VMAJ' => 8, 'VMIN' => 8, 'VREV' => 8, 'FMBW' => 16, 'FMBH' => 16, 'PICW' => 24, 'PICH' => 24, 'PICX' => 8, 'PICY' => 8, 'FRN' => 32, 'FRD' => 32, 'PARN' => 24, 'PARD' => 24, 'CS' => 8, 'NOMBR' => 24, 'QUAL' => 6, 'KFGSHIFT' => 5, 'PF' => 2));
if (!$h) {
throw new PEAR_Exception("Stream is undecodable due to a truncated header.", OGG_ERROR_UNDECODABLE);
}
// Theora version
// Seems overly strict but this is what the spec says
// VREV is for backwards-compatible changes, apparently
if ($h['VMAJ'] != 3 || $h['VMIN'] != 2) {
throw new PEAR_Exception("Stream is undecodable due to an invalid theora version.", OGG_ERROR_UNDECODABLE);
}
$this->_theoraVersion = "{$h['VMAJ']}.{$h['VMIN']}.{$h['VREV']}";
// Frame height/width
if (!$h['FMBW'] || !$h['FMBH']) {
throw new PEAR_Exception("Stream is undecodable because it has frame size of zero.", OGG_ERROR_UNDECODABLE);
}
$this->_frameWidth = $h['FMBW'] * 16;
$this->_frameHeight = $h['FMBH'] * 16;
// Picture height/width
if ($h['PICW'] > $this->_frameWidth || $h['PICH'] > $this->_frameHeight) {
throw new PEAR_Exception("Stream is undecodable because the picture width is greater than the frame width.", OGG_ERROR_UNDECODABLE);
}
$this->_pictureWidth = $h['PICW'];
$this->_pictureHeight = $h['PICH'];
// Picture offset
$this->_offsetX = $h['PICX'];
$this->_offsetY = $h['PICY'];
// Frame rate
$this->_frameRate = $h['FRD'] == 0 ? 0 : $h['FRN'] / $h['FRD'];
// Physical aspect ratio
if (!$h['PARN'] || !$h['PARD']) {
$this->_physicalAspectRatio = 1;
} else {
$this->_physicalAspectRatio = $h['PARN'] / $h['PARD'];
}
// Color space
$colorSpaces = array(0 => 'Undefined', 1 => 'Rec. 470M', 2 => 'Rec. 470BG');
if (isset($colorSpaces[$h['CS']])) {
$this->_colorSpace = $colorSpaces[$h['CS']];
} else {
$this->_colorSpace = 'Unknown (reserved)';
}
$this->_nomBitrate = $h['NOMBR'];
$this->_quality = $h['QUAL'];
$this->_kfgShift = $h['KFGSHIFT'];
$pixelFormats = array(0 => '4:2:0', 1 => 'Unknown (reserved)', 2 => '4:2:2', 3 => '4:4:4');
$this->_pixelFormat = $pixelFormats[$h['PF']];
switch ($h['PF']) {
case 0:
$h['NSBS'] = floor(($h['FMBW'] + 1) / 2) * floor(($h['FMBH'] + 1) / 2) + 2 * floor(($h['FMBW'] + 3) / 4) * floor(($h['FMBH'] + 3) / 4);
$h['NBS'] = 6 * $h['FMBW'] * $h['FMBH'];
break;
case 2:
$h['NSBS'] = floor(($h['FMBW'] + 1) / 2) * floor(($h['FMBH'] + 1) / 2) + 2 * floor(($h['FMBW'] + 3) / 4) * floor(($h['FMBH'] + 1) / 2);
$h['NBS'] = 8 * $h['FMBW'] * $h['FMBH'];
break;
case 3:
$h['NSBS'] = 3 * floor(($h['FMBW'] + 1) / 2) * floor(($h['FMBH'] + 1) / 2);
$h['NBS'] = 12 * $h['FMBW'] * $h['FMBH'];
break;
default:
$h['NSBS'] = $h['NBS'] = 0;
}
$h['NMBS'] = $h['FMBW'] * $h['FMBH'];
$this->_idHeader = $h;
}
