Timecode Index Object
* is used, it is recommended that timecodes be stored as a Payload Extension
* System on the appropriate stream. It is also recommended that every
* timecode appearing in the ASF file have a corresponging index entry.
*
* The index is designed to be broken into blocks to facilitate storage that is
* more space-efficient by using 32-bit offsets relative to a 64-bit base. That
* is, each index block has a full 64-bit offset in the block header that is
* added to the 32-bit offsets found in each index entry. If a file is larger
* than 2^32 bytes, then multiple index blocks can be used to fully index the
* entire large file while still keeping index entry offsets at 32 bits.
*
* To locate an object with a particular timecode in an ASF file, one would
* typically look through the Timecode Index Object in blocks of the
* appropriate range and try to locate the nearest possible timecode. The
* corresponding Offset field values of the Index Entry are byte
* offsets that, when combined with the Block Position value of the Index
* Block, indicate the starting location in bytes of an ASF Data Packet relative
* to the start of the first ASF Data Packet in the file.
*
* Any ASF file containing a Timecode Index Object shall also contain a
* Timecode Index Parameters Object in its
* {@link ASF_Object_Header ASF Header}.
*
* @package php-reader
* @subpackage ASF
* @author Sven Vollbehr
* @copyright Copyright (c) 2008 The PHP Reader Project Workgroup
* @license http://code.google.com/p/php-reader/wiki/License New BSD License
* @version $Rev: 108 $
*/
final class ASF_Object_TimecodeIndex extends ASF_Object
{
/**
* Indicates that the index type is Nearest Past Data Packet. The Nearest
* Past Data Packet indexes point to the data packet whose presentation time
* is closest to the index entry time.
*/
const NEAREST_PAST_DATA_PACKET = 1;
/**
* Indicates that the index type is Nearest Past Media. The Nearest Past
* Object indexes point to the closest data packet containing an entire object
* or first fragment of an object.
*/
const NEAREST_PAST_MEDIA = 2;
/**
* Indicates that the index type is Nearest Past Cleanpoint. The Nearest Past
* Cleanpoint indexes point to the closest data packet containing an entire
* object (or first fragment of an object) that has the Cleanpoint Flag set.
*
* Nearest Past Cleanpoint is the most common type of index.
*/
const NEAREST_PAST_CLEANPOINT = 3;
/** @var Array */
private $_indexSpecifiers = array();
/** @var Array */
private $_indexBlocks = array();
/**
* Constructs the class with given parameters and reads object related data
* from the ASF file.
*
* @param Reader $reader The reader object.
* @param Array $options The options array.
*/
public function __construct($reader, &$options = array())
{
parent::__construct($reader, $options);
$this->_reader->skip(4);
$indexSpecifiersCount = $this->_reader->readUInt16LE();
$indexBlocksCount = $this->_reader->readUInt32LE();
for ($i = 0; $i < $indexSpecifiersCount; $i++)
$this->_indexSpecifiers[] = array
("streamNumber" => $this->_reader->readUInt16LE(),
"indexType" => $this->_reader->readUInt16LE());
for ($i = 0; $i < $indexBlocksCount; $i++) {
$indexEntryCount = $this->_reader->readUInt32LE();
$timecodeRange = $this->_reader->readUInt16LE();
$blockPositions = array();
for ($i = 0; $i < $indexSpecifiersCount; $i++)
$blockPositions[] = $this->_reader->readInt64LE();
$indexEntries = array();
for ($i = 0; $i < $indexEntryCount; $i++) {
$timecode = $this->_reader->readUInt32LE();
$offsets = array();
for ($i = 0; $i < $indexSpecifiersCount; $i++)
$offsets[] = $this->_reader->readUInt32LE();
$indexEntries[] = array
("timecode" => $timecode,
"offsets" => $offsets);
}
$this->_indexBlocks[] = array
("timecodeRange" => $timecodeRange,
"blockPositions" => $blockPositions,
"indexEntries" => $indexEntries);
}
}
/**
* Returns an array of index specifiers. Each entry consists of the following
* keys.
*
* o streamNumber -- Specifies the stream number that the Index
* Specifiers refer to. Valid values are between 1 and 127.
*
* o indexType -- Specifies the type of index.
*
* @return Array
*/
public function getIndexSpecifiers() { return $this->_indexSpecifiers; }
/**
* Returns an array of index entries. Each entry consists of the following
* keys.
*
* o timecodeRange -- Specifies the timecode range for this block.
* Subsequent blocks must contain range numbers greater than or equal to
* this one.
*
* o blockPositions -- Specifies a list of byte offsets of the beginnings of
* the blocks relative to the beginning of the first Data Packet (for
* example, the beginning of the Data Object + 50 bytes).
*
* o indexEntries -- An array that consists of the following keys
* o timecode -- This is the 4-byte timecode for these entries.
* o offsets -- Specifies the offset. An offset value of 0xffffffff
* indicates an invalid offset value.
*
* @return Array
*/
public function getIndexBlocks() { return $this->_indexBlocks; }
}