Sub-Sample Information Box is designed to contain sub-sample * information. * * A sub-sample is a contiguous range of bytes of a sample. The specific * definition of a sub-sample shall be supplied for a given coding system (e.g. * for ISO/IEC 14496-10, Advanced Video Coding). In the absence of such a * specific definition, this box shall not be applied to samples using that * coding system. * * If subsample_count is 0 for any entry, then those samples have no subsample * information and no array follows. The table is sparsely coded; the table * identifies which samples have sub-sample structure by recording the * difference in sample-number between each entry. The first entry in the table * records the sample number of the first sample having sub-sample information. * * Note: It is possible to combine subsamplePriority and discardable such that * when subsamplePriority is smaller than a certain value, discardable is set to * 1. However, since different systems may use different scales of priority * values, to separate them is safe to have a clean solution for discardable * sub-samples. * * @package php-reader * @subpackage ISO 14496 * @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: 92 $ */ final class ISO14496_Box_SUBS extends ISO14496_Box_Full { /** @var Array */ private $_subSampleTable = array(); /** * Constructs the class with given parameters and reads box related data from * the ISO Base Media file. * * @param Reader $reader The reader object. */ public function __construct($reader, &$options = array()) { parent::__construct($reader, $options); $entryCount = $this->_reader->readUInt32BE(); for ($i = 0; $i < $entryCount; $i++) { $entry = array(); $entry["sampleDelta"] = $this->_reader->readUInt32BE(); $entry["subsamples"] = array(); if (($subsampleCount = $this->_reader->readUInt16BE()) > 0) { for ($j = 0; $j < $subsampleCount; $j++) { $subsample = array(); if ($this->getVersion() == 1) $subsample["subsampleSize"] = $this->_reader->readUInt32BE(); else $subsample["subsampleSize"] = $this->_reader->readUInt16BE(); $subsample["subsamplePriority"] = $this->_reader->readInt8(); $subsample["discardable"] = $this->_reader->readInt8(); $this->_reader->skip(4); $entry["subsamples"][] = $subsample; } $this->_subSampleTable[] = $entry; } } } /** * Returns an array of values. Each entry is an array containing the following * keys. * o sampleDelta -- an integer that specifies the sample number of the * sample having sub-sample structure. It is coded as the difference * between the desired sample number, and the sample number indicated in * the previous entry. If the current entry is the first entry, the value * indicates the sample number of the first sample having sub-sample * information, that is, the value is the difference between the sample * number and zero (0). * o subsamples -- an array of subsample arrays, each containing the * following keys. * o subsampleSize -- an integer that specifies the size, in bytes, of * the current sub-sample. * o subsamplePriority -- an integer specifying the degradation priority * for each sub-sample. Higher values of subsamplePriority, indicate * sub-samples which are important to, and have a greater impact on, * the decoded quality. * o discardable -- equal to 0 means that the sub-sample is required to * decode the current sample, while equal to 1 means the sub-sample is * not required to decode the current sample but may be used for * enhancements, e.g., the sub-sample consists of supplemental * enhancement information (SEI) messages. * * @return Array */ public function getSubSampleTable() { return $this->_subSampleTable; } }