PHP MP3 Parser

parser.php

<?php

/* 
 * A tiny parser which parses ID3 tags and MP3 frames.
 */

function parseMP3($mp3file) {

	function _parseID3TagsV2($data) {
		define("HEADER_LENGTH", 10);
		define("HEADER_BODY_LENGTH_INFO_OFFSET", 6);
		define("HEADER_BODY_LENGTH_INFO_LENGTH", 4);
		define("FRAME_HEADER_LENGTH", 10);
		define("FRAME_ID_LENGTH", 4);
		define("FRAME_BODY_LENGTH_INFO_LENGTH", 4);

		function MASK($bits) { 
			return (1 << ($bits)) - 1;
		}
		function _readUInt28($bytes) {
			$BITSUSED = 7; $val = 0;
			foreach(str_split($bytes) as $byte) {
				$val = ($val << $BITSUSED) | (ord($byte) & MASK($BITSUSED));
			}
			return min($val, MASK($BITSUSED * 4));
		}

		$tags = array();
		$ID3TagHeader = substr($data, 0, HEADER_LENGTH);
		$ID3TagBodyInfo = substr($data, HEADER_BODY_LENGTH_INFO_OFFSET, HEADER_BODY_LENGTH_INFO_LENGTH);
		$ID3TagBodyLength = _readUInt28($ID3TagBodyInfo);
		$readHead = HEADER_LENGTH;
		while ($readHead < $ID3TagBodyLength) {
			$frameHeader = substr($data, $readHead, FRAME_HEADER_LENGTH);
			$frameID = substr($frameHeader, 0, FRAME_ID_LENGTH);
			$frameBodyLengthInfo = substr($frameHeader, FRAME_ID_LENGTH, FRAME_BODY_LENGTH_INFO_LENGTH);
			$frameBodyLength = _readUInt28($frameBodyLengthInfo);
			$frameBody = substr($data, $readHead + FRAME_HEADER_LENGTH, $frameBodyLength);
			$textEncodingType = intval($frameBody[0]);
			$frameContent = substr($frameBody, 1, strlen($frameBody) -1);
			$tags[$frameID] = $frameContent;
			$readHead += $FRAME_HEADER_LENGTH + $frameBodyLength;
		}
		return array($tags, $readHead);
	}

	function _parseMP3Data($data, $size, $inReadHead=0) {
		// $data = str_split($data);
		$readHead = $inReadHead;
		$foundFirstFrame = False;
		$MP3BitrateLookup = array(0, 32000, 40000, 48000, 56000, 64000, 80000, 96000, 112000, 128000, 160000, 192000, 224000, 256000, 320000, 0);
		$parsedFrameCount = 0;
		$skippedByteCount = 0;
		while(True) {
			$remainingLength = $size - $readHead;
			if ($remainingLength < 2) {
				break;
			}
			$frameSync = (ord($data[$readHead]) << 8) | (ord($data[$readHead + 1]) & (0x80 | 0x40 | 0x20));
			if ($frameSync != 0xffe0) {
				print "skip $readHead\n";
				$readHead += 1;
				$skippedByteCount += 1;
				continue;
			}
			if ($remainingLength < 6) {
				break;
			}
			$audioVersion = (ord($data[$readHead + 1]) >> 3) & 0x03;
			$layer = (ord($data[$readHead + 1]) >> 1) & 0x03;
			$hasCRC = !(ord($data[$readHead + 1]) & 0x01);
			$bitrateIndex = ord($data[$readHead + 2]) >> 4;
			$sampleRateIndex = ord($data[$readHead + 2]) >> 2 & 0x03;
			$bitrate = $MP3BitrateLookup[$bitrateIndex];
			// print "audioVersion:$audioVersion, layer:$layer, sampleRateIndex:$sampleRateIndex, bitrate:$bitrate\n";
			if (!($audioVersion == 0x03 and $layer == 0x01 and $sampleRateIndex == 0x00)) {
				// Test
			}
			$hasPadding = (!(!((ord($data[$readHead + 2]) >> 1) & 0x01)));
			$padding = 0; if ($hasPadding) { $padding = 1; };
			$CRCPadding = 0; if ($hasCRC) { $CRCPadding = 2; }; 
			$frameLength = intval((144 * $bitrate / 44100)) + $padding + $CRCPadding;
			$readHead += $frameLength;
			if ($remainingLength < $frameLength) {
				break;
			}
			$parsedFrameCount++;
		}
		print "parsedFrameCount:".$parsedFrameCount."\n";
		print "skippedByteCount:".$skippedByteCount."\n";
		return True;
	}

	$handle = fopen($mp3file, "rb");
	$size = filesize($mp3file);
	$data = fread($handle, $size);
	$readHead = 0;
	$tags = NULL;
	if ($data[0] == 'I' && $data[1] == 'D' && $data[2] == '3') {
		$result = _parseID3TagsV2($data);
		$tags = $result[0];
		$readHead = $result[1];
	}
	return array(_parseMP3Data($data, $size, 0), $tags);
}

?>

zonble 大
line 42 should be:
$readHead += FRAME_HEADER_LENGTH + $frameBodyLength;

you have an additional '$' for FRAME_HEADER_LENGTH