Relative volume adjustment (2) frame is a more subjective frame than * the previous ones. It allows the user to say how much he wants to * increase/decrease the volume on each channel when the file is played. The * purpose is to be able to align all files to a reference volume, so that you * don't have to change the volume constantly. This frame may also be used to * balance adjust the audio. The volume adjustment is encoded as a fixed point * decibel value, 16 bit signed integer representing (adjustment*512), giving * +/- 64 dB with a precision of 0.001953125 dB. E.g. +2 dB is stored as $04 00 * and -2 dB is $FC 00. * * There may be more than one RVA2 frame in each tag, but only one with the same * identification string. * * @package php-reader * @subpackage ID3 * @author Sven Vollbehr * @author Ryan Butterfield * @copyright Copyright (c) 2008 The PHP Reader Project Workgroup * @license http://code.google.com/p/php-reader/wiki/License New BSD License * @version $Rev: 105 $ * @since ID3v2.4.0 */ final class ID3_Frame_RVA2 extends ID3_Frame { /** * The channel type key. * * @see $types * @var string */ const channelType = "channelType"; /** * The volume adjustment key. Adjustments are +/- 64 dB with a precision of * 0.001953125 dB. * * @var string */ const volumeAdjustment = "volumeAdjustment"; /** * The peak volume key. * * @var string */ const peakVolume = "peakVolume"; /** * The list of channel types. * * @var Array */ public static $types = array ("Other", "Master volume", "Front right", "Front left", "Back right", "Back left", "Front centre", "Back centre", "Subwoofer"); /** @var string */ private $_device; /** @var Array */ private $_adjustments; /** * 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) return; list ($this->_device, $this->_data) = $this->explodeString8($this->_data, 2); for ($i = $j = 0; $i < 9; $i++) { $this->_adjustments[$i] = array (self::channelType => Transform::fromInt8($this->_data[$j++]), self::volumeAdjustment => Transform::fromInt16BE(substr($this->_data, $j++, 2)) / 512.0); $j++; $bitsInPeak = Transform::fromInt8($this->_data[$j++]); $bytesInPeak = $bitsInPeak > 0 ? ceil($bitsInPeak / 8) : 0; switch ($bytesInPeak) { case 8: case 7: case 6: case 5: $this->_adjustments[$i][self::peakVolume] = Transform::fromInt64BE(substr($this->_data, $j, $bytesInPeak)); break; case 4: case 3: $this->_adjustments[$i][self::peakVolume] = Transform::fromUInt32BE(substr($this->_data, $j, $bytesInPeak)); break; case 2: $this->_adjustments[$i][self::peakVolume] = Transform::fromUInt16BE(substr($this->_data, $j, $bytesInPeak)); break; case 1: $this->_adjustments[$i][self::peakVolume] = Transform::fromUInt8(substr($this->_data, $j, $bytesInPeak)); } $j += $bytesInPeak; } } /** * Returns the device where the adjustments should apply. * * @return string */ public function getDevice() { return $this->_device; } /** * Sets the device where the adjustments should apply. * * @param string $device The device. */ public function setDevice($device) { $this->_device = $device; } /** * Returns the array containing volume adjustments for each channel. Volume * adjustments are arrays themselves containing the following keys: * channelType, volumeAdjustment, peakVolume. * * @return Array */ public function getAdjustments() { return $this->_adjustments; } /** * Sets the array of volume adjustments for each channel. Each volume * adjustment is an array too containing the following keys: channelType, * volumeAdjustment, peakVolume. * * @param Array $adjustments The volume adjustments array. */ public function setAdjustments($adjustments) { $this->_adjustments = $adjustments; } /** * Returns the frame raw data. * * @return string */ public function __toString() { $data = $this->_device . "\0"; foreach ($this->_adjustments as $channel) { $data .= Transform::toInt8($channel[self::channelType]) . Transform::toInt16BE($channel[self::volumeAdjustment] * 512); if (abs($channel[self::peakVolume]) <= 0xff) $data .= Transform::toInt8(8) . Transform::toUInt8($channel[self::peakVolume]); else if (abs($channel[self::peakVolume]) <= 0xffff) $data .= Transform::toInt8(16) . Transform::toUInt16BE($channel[self::peakVolume]); else if (abs($channel[self::peakVolume]) <= 0xffffffff) $data .= Transform::toInt8(32) . Transform::toUInt32BE($channel[self::peakVolume]); else $data .= Transform::toInt8(64) . Transform::toInt64BE($channel[self::peakVolume]); // UInt64 } $this->setData($data); return parent::__toString(); } }