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<?php
/* vim: set expandtab tabstop=4 shiftwidth=4: */
// +----------------------------------------------------------------------------+
// | File_Ogg PEAR Package for Accessing Ogg Bitstreams |
// | Copyright (c) 2005-2007 |
// | David Grant <david@grant.org.uk> |
// | Tim Starling <tstarling@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 |
// +----------------------------------------------------------------------------+
/**
* Parent class for media bitstreams
* Contains some functions common to various media formats
*/
abstract class File_Ogg_Media extends File_Ogg_Bitstream
{
/**
* Maximum size of header comment to parse.
* Set to 1 MB by default. Make sure this is less than your PHP memory_limit.
*/
const COMMENT_MAX_SIZE = 1000000;
/**
* Array to hold each of the comments.
*
* @access private
* @var array
*/
var $_comments = array();
/**
* Vendor string for the stream.
*
* @access private
* @var string
*/
var $_vendor;
/**
* Length of the stream in seconds
*/
var $_streamLength;
/* Start offset of the stream in seconds */
var $_startOffset = 0;
/**
* Get a short string describing the type of the stream
* @return string
*/
abstract function getType();
/**
* Get the 6-byte identification string expected in the common header
* @return string
*/
function getIdentificationString()
{
return '';
}
/**
* @access private
* @param int $packetType
* @param int $pageOffset
*/
function _decodeCommonHeader($packetType, $pageOffset)
{
fseek($this->_filePointer, $this->_streamData['pages'][$pageOffset]['body_offset'], SEEK_SET);
if ($packetType !== false) {
// Check if this is the correct header.
$packet = unpack("Cdata", fread($this->_filePointer, 1));
if ($packet['data'] != $packetType)
throw new OggException("Stream Undecodable", OGG_ERROR_UNDECODABLE);
// The following six characters should be equal to getIdentificationString()
$id = $this->getIdentificationString();
if ($id !== '' && fread($this->_filePointer, strlen($id)) !== $id)
throw new OggException("Stream is undecodable due to a malformed header.", OGG_ERROR_UNDECODABLE);
} // else seek only, no common header
}
/**
* Parse a Vorbis-style comments header.
*
* This function parses the comments header. The comments header contains a series of
* UTF-8 comments related to the audio encoded in the stream. This header also contains
* a string to identify the encoding software. More details on the comments header can
* be found at the following location: http://xiph.org/vorbis/doc/v-comment.html
*
* @access private
*/
function _decodeBareCommentsHeader()
{
// Decode the vendor string length as a 32-bit unsigned integer.
$vendor_len = unpack("Vdata", fread($this->_filePointer, 4));
if ( $vendor_len['data'] > 0 ) {
// Retrieve the vendor string from the stream.
$this->_vendor = fread($this->_filePointer, $vendor_len['data']);
} else {
$this->_vendor = '';
}
// Decode the size of the comments list as a 32-bit unsigned integer.
$comment_list_length = unpack("Vdata", fread($this->_filePointer, 4));
// Iterate through the comments list.
for ($i = 0; $i < $comment_list_length['data']; ++$i) {
// Unpack the length of this comment.
$comment_length = unpack("Vdata", fread($this->_filePointer, 4));
// If the comment length is greater than specified limit, skip it.
if ( $comment_length['data'] > self::COMMENT_MAX_SIZE ) {
continue;
}
// Comments are in the format 'ARTIST=Super Furry Animals', so split it on the equals character.
// NOTE: Equals characters are strictly prohibited in either the COMMENT or DATA parts.
$comment = explode("=", fread($this->_filePointer, $comment_length['data']));
$comment_title = (string) $comment[0];
$comment_value = (string) $comment[1];
// Check if the comment type (e.g. ARTIST) already exists. If it does,
// take the new value, and the existing value (or array) and insert it
// into a new array. This is important, since each comment type may have
// multiple instances (e.g. ARTIST for a collaboration) and we should not
// overwrite the previous value.
if (isset($this->_comments[$comment_title])) {
if (is_array($this->_comments[$comment_title]))
$this->_comments[$comment_title][] = $comment_value;
else
$this->_comments[$comment_title] = array($this->_comments[$comment_title], $comment_value);
} else
$this->_comments[$comment_title] = $comment_value;
}
}
/**
* Number of channels used in this stream
*
* This function returns the number of channels used in this stream. This
* can range from 1 to 255, but will likely be 2 (stereo) or 1 (mono).
*
* @access public
* @return int
* @see File_Ogg_Vorbis::isMono()
* @see File_Ogg_Vorbis::isStereo()
* @see File_Ogg_Vorbis::isQuadrophonic()
*/
function getChannels()
{
return ($this->_channels);
}
/**
* Provides a list of the comments extracted from the Vorbis stream.
*
* It is recommended that the user fully inspect the array returned by this function
* rather than blindly requesting a comment in false belief that it will always
* be present. Whilst the Vorbis specification dictates a number of popular
* comments (e.g. TITLE, ARTIST, etc.) for use in Vorbis streams, they are not
* guaranteed to appear.
*
* @access public
* @return array
*/
function getCommentList()
{
return (array_keys($this->_comments));
}
/**
* Provides an interface to the numerous comments located with a Vorbis stream.
*
* A Vorbis stream may contain one or more instances of each comment, so the user
* should check the variable type before printing out the result of this method.
* The situation in which multiple instances of a comment occurring are not as
* rare as one might think, since they are conceivable at least for ARTIST comments
* in the situation where a track is a duet.
*
* @access public
* @param string $commentTitle Comment title to search for, e.g. TITLE.
* @param string $separator String to separate multiple values.
* @return string
*/
function getField($commentTitle, $separator = ", ")
{
if (isset($this->_comments[$commentTitle])) {
if (is_array($this->_comments[$commentTitle]))
return (implode($separator, $this->_comments[$commentTitle]));
else
return ($this->_comments[$commentTitle]);
} else
// The comment doesn't exist in this file. The user should've called getCommentList first.
return ("");
}
/**
* Get the entire comments array.
* May return an empty array if the bitstream does not support comments.
*
* @access public
* @return array
*/
function getComments() {
return $this->_comments;
}
/**
* Vendor of software used to encode this stream.
*
* Gives the vendor string for the software used to encode this stream.
* It is common to find libVorbis here. The majority of encoders appear
* to use libvorbis from Xiph.org.
*
* @access public
* @return string
*/
function getVendor()
{
return ($this->_vendor);
}
/**
* Get an associative array containing header information about the stream
* @access public
* @return array
*/
function getHeader()
{
return array();
}
/**
* Get the length of the stream in seconds
* @return float
*/
function getLength()
{
return $this->_streamLength;
}
/**
* Get the start offset of the stream in seconds
*
* @return float
*/
function getStartOffset(){
return $this->_startOffset;
}
}
|
