Audio seek point index or * ASPI frame makes seeking easier by providing a list a seek points within the * audio file. The seek points are a fractional offset within the audio data, * providing a starting point from which to find an appropriate point to start * decoding. The presence of an ASPI frame requires the existence of a * {@link ID3_Frame_TLEN} frame, indicating the duration of the file in * milliseconds. There may only be one audio seek point index frame in a tag. * * @todo Data parsing and write support * @package php-reader * @subpackage ID3 * @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: 75 $ * @since ID3v2.4.0 */ final class ID3_Frame_ASPI extends ID3_Frame { /** @var integer */ private $_dataStart; /** @var integer */ private $_dataLength; /** @var integer */ private $_size; /** @var Array */ private $_fractions = array(); /** * Constructs the class with given parameters and parses object related data. * * @param Reader $reader The reader object. * @param Array $options The options array. */ public function __construct($reader = null, &$options = array()) { parent::__construct($reader, $options); if ($reader === null) throw new ID3_Exception("Write not supported yet"); $this->_dataStart = Transform::fromInt32BE(substr($this->_data, 0, 4)); $this->_dataLength = Transform::fromInt32BE(substr($this->_data, 4, 4)); $this->_size = Transform::fromInt16BE(substr($this->_data, 8, 2)); $bitsPerPoint = Transform::fromInt8($this->_data[10]); /*for ($i = 0, $offset = 11; $i < $this->_size; $i++) { if ($bitsPerPoint == 16) { $this->_fractions[$i] = substr($this->_data, $offset, 2); $offset += 2; } else { $this->_fractions[$i] = substr($this->_data, $offset, 1); $offset ++; } }*/ } /** * Returns the byte offset from the beginning of the file. * * @return integer */ public function getDataStart() { return $this->_dataStart; } /** * Sets the byte offset from the beginning of the file. * * @param integer $dataStart The offset. */ public function setDataStart($dataStart) { $this->_dataStart = $dataStart; } /** * Returns the byte length of the audio data being indexed. * * @return integer */ public function getDataLength() { return $this->_dataLength; } /** * Sets the byte length of the audio data being indexed. * * @param integer $dataLength The length. */ public function setDataLength($dataLength) { $this->_dataLength = $dataLength; } /** * Returns the number of index points in the frame. * * @return integer */ public function getSize() { return count($this->_fractions); } /** * Returns the numerator of the fraction representing a relative position in * the data or false if index not defined. The denominator is 2 * to the power of b. * * @param integer $index The fraction numerator. * @return integer */ public function getFractionAt($index) { if (isset($this->_fractions[$index])) return $this->_fractions[$index]; return false; } }