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<?php
/* vim: set expandtab tabstop=4 shiftwidth=4: */
// +----------------------------------------------------------------------------+
// | File_Ogg PEAR Package for Accessing Ogg Bitstreams |
// | Copyright (c) 2013 |
// | Jan Gerber <jgerber@wikimedia.org> |
// +----------------------------------------------------------------------------+
// | This library is free software; you can redistribute it and/or |
// | modify it under the terms of the GNU Lesser General Public |
// | License as published by the Free Software Foundation; either |
// | version 2.1 of the License, or (at your option) any later version. |
// | |
// | This library is distributed in the hope that it will be useful, |
// | but WITHOUT ANY WARRANTY; without even the implied warranty of |
// | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU |
// | Lesser General Public License for more details. |
// | |
// | You should have received a copy of the GNU Lesser General Public |
// | License along with this library; if not, write to the Free Software |
// | Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA |
// +----------------------------------------------------------------------------+
define( 'OGG_OPUS_COMMENTS_PAGE_OFFSET', 1 );
/**
* @author Jan Gerber <jgerber@wikimedia.org>
* @category File
* @copyright Jan Gerber <jgerber@wikimedia.org>
* @license http://www.gnu.org/copyleft/lesser.html GNU LGPL
* @link http://pear.php.net/package/File_Ogg
* @link http://www.opus-codec.org/
* @package File_Ogg
* @version 1
*/
class File_Ogg_Opus extends File_Ogg_Media
{
/**
* @access private
*/
function __construct($streamSerial, $streamData, $filePointer)
{
parent::__construct($streamSerial, $streamData, $filePointer);
$this->_decodeHeader();
$this->_decodeCommentsHeader();
$endSec = $this->getSecondsFromGranulePos( $this->_lastGranulePos );
$startSec = $this->getSecondsFromGranulePos( $this->_firstGranulePos );
if( $startSec > 1){
$this->_streamLength = $endSec - $startSec;
$this->_startOffset = $startSec;
}else{
$this->_streamLength = $endSec;
}
$this->_avgBitrate = $this->_streamLength ? ($this->_streamSize * 8) / $this->_streamLength : 0;
}
function getSecondsFromGranulePos( $granulePos ){
return (( '0x' . substr( $granulePos, 0, 8 ) ) * pow(2, 32)
+ ( '0x' . substr( $granulePos, 8, 8 ) )
- $this->_header['pre_skip'])
/ 48000;
}
/**
* Get a short string describing the type of the stream
* @return string
*/
function getType()
{
return 'Opus';
}
/**
* Decode the stream header
* @access private
*/
function _decodeHeader()
{
fseek($this->_filePointer, $this->_streamData['pages'][0]['body_offset'], SEEK_SET);
// The first 8 characters should be "OpusHead".
if (fread($this->_filePointer, 8) != 'OpusHead')
throw new OggException("Stream is undecodable due to a malformed header.", OGG_ERROR_UNDECODABLE);
$this->_header = File_Ogg::_readLittleEndian($this->_filePointer, array(
'opus_version' => 8,
'nb_channels' => 8,
'pre_skip' => 16,
'audio_sample_rate' => 32,
'output_gain' => 16,
'channel_mapping_family'=> 8,
));
$this->_channels = $this->_header['nb_channels'];
}
/**
* Get an associative array containing header information about the stream
* @access public
* @return array
*/
function getHeader() {
return $this->_header;
}
function getSampleRate()
{
//Opus always outputs 48kHz, the header only lists
//the samplerate of the source as reference
return 48000;
}
/**
* Decode the comments header
* @access private
*/
function _decodeCommentsHeader()
{
$id = 'OpusTags';
$this->_decodeCommonHeader(false, OGG_OPUS_COMMENTS_PAGE_OFFSET);
if(fread($this->_filePointer, strlen($id)) !== $id)
throw new OggException("Stream is undecodable due to a malformed header.", OGG_ERROR_UNDECODABLE);
$this->_decodeBareCommentsHeader();
}
}
?>
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