<?php
class MP3_Crop {
/**
* mp3/mpeg file name
* @var boolean
*/
var $file = false;
/**
* version of bitrate
* @var integer
*/
var $bitrate = 0;
var $layer;
/**
* Bytes in file
* @var integer
*/
var $filesize = -1;
/**
* Byte at which the first mpeg header was found
* @var integer
*/
var $frameoffset = -1;
/**
* length of mp3 format hh:ss
* @var string
*/
/**
* length of mp3 in seconds
* @var string
*/
var $length = false;
/*
* creates a new id3 object
* and loads a tag from a file.
*
*/
function MP3_Crop()
{
}
/**
* reads the given file and parse it
*
* @param string $file the name of the file to parse
* @return mixed PEAR_Error on error
* @access public
*/
function read($file)
{
$this->file = $file;
return $this->_readframe();
}
/**
* update the id3v1 tags on the file.
* Note: If/when ID3v2 is implemented this method will probably get another
* parameters.
*
* @param boolean $v1 if true update/create an id3v1 tag on the file. (defaults to true)
*
* @access public
*/
function write($cropFile, $length = 20)
{
$size = ($length * $this->bitrate * 1000) / 8;
$f = fopen($this->file, 'rb');
if (!$f)
{
return false;
}
$content = fread($f, $size);
fclose($f);
$f = fopen($cropFile, 'wb');
if (!$f)
{
return false;
}
fwrite($f, $content);
fclose($f);
return true;
}
/**
* reads a frame from the file
*
* @return mixed PEAR_Error when fails
* @access private
*/
function _readframe()
{
$file = $this->file;
if (! ($f = fopen($file, 'rb')) )
{
return false;
}
$this->filesize = filesize($file);
do
{
while (fread($f,1) != Chr(255))
{
// Find the first frame
if (feof($f))
{
return false;
}
}
fseek($f, ftell($f) - 1); // back up one byte
$frameoffset = ftell($f);
$r = fread($f, 4);
// Binary to Hex to a binary sting. ugly but best I can think of.
$bits = unpack('H*bits', $r);
$bits = base_convert($bits['bits'],16,2);
} while (!$bits[8] and !$bits[9] and !$bits[10]); // 1st 8 bits true from the while
$this->frameoffset = $frameoffset;
fclose($f);
if ($bits[11] == 0) {
$bitrates = array(
'1' => array(0, 32, 48, 56, 64, 80, 96, 112, 128, 144, 160, 176, 192, 224, 256, 0),
'2' => array(0, 8, 16, 24, 32, 40, 48, 56, 64, 80, 96, 112, 128, 144, 160, 0),
'3' => array(0, 8, 16, 24, 32, 40, 48, 56, 64, 80, 96, 112, 128, 144, 160, 0),
);
} else if ($bits[12] == 0) {
$bitrates = array(
'1' => array(0, 32, 48, 56, 64, 80, 96, 112, 128, 144, 160, 176, 192, 224, 256, 0),
'2' => array(0, 8, 16, 24, 32, 40, 48, 56, 64, 80, 96, 112, 128, 144, 160, 0),
'3' => array(0, 8, 16, 24, 32, 40, 48, 56, 64, 80, 96, 112, 128, 144, 160, 0),
);
} else {
$bitrates = array(
'1' => array(0, 32, 64, 96, 128, 160, 192, 224, 256, 288, 320, 352, 384, 416, 448, 0),
'2' => array(0, 32, 48, 56, 64, 80, 96, 112, 128, 160, 192, 224, 256, 320, 384, 0),
'3' => array(0, 32, 40, 48, 56, 64, 80, 96, 112, 128, 160, 192, 224, 256, 320, 0),
);
}
$layer = array(
array(0,3),
array(2,1),
);
$this->layer = $layer[$bits[13]][$bits[14]];
$bitrate = 0;
if ($bits[16] == 1) $bitrate += 8;
if ($bits[17] == 1) $bitrate += 4;
if ($bits[18] == 1) $bitrate += 2;
if ($bits[19] == 1) $bitrate += 1;
$this->bitrate = $bitrates[$this->layer][$bitrate];
if ($this->bitrate == 0)
{
$this->length = -1;
return false;
}
$s = ((8 * filesize($this->file)) / 1000) / $this->bitrate;
$this->length = (int)$s;
return true;
}
};
?>
