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; } }