ID3::parseMP3FrameHeader() - Code Metrics - chillerlan/php-id3tag - Measure and Improve Code Quality continuously with Scrutinizer

ID3::parseMP3FrameHeader() D
last analyzed 2021-05-10 10:21 UTC

↳ Parent: ID3

Complexity

Conditions	19
Paths	59

Size

Total Lines	107
Code Lines	53

Duplication

Lines	0
Ratio	0 %

Importance

Changes	1
Bugs	0	Features	0

Metric	Value
cc	19
eloc	53
c	1
b	0
f	0
nc	59
nop	1
dl	0
loc	107
rs	4.5166

How to fix Long Method Complexity

<?php
/**
 * Class ID3
 *
 * @created      22.09.2018
 * @author       smiley <[email protected]>
 * @copyright    2018 smiley
 * @license      MIT
 */

namespace chillerlan\ID3Tag;

use stdClass;

use function fclose, file_exists, floor, fopen, fread, fseek, ftell, in_array, is_file,
	is_readable, is_resource, ord, realpath, round, sprintf, strlen, strtolower, substr, unpack;

use const PHP_INT_MAX, SEEK_END, SEEK_SET;

/**
 * @link http://id3.org/id3guide
 * @link http://www.mp3-tech.org/
 * @link https://en.wikipedia.org/wiki/ID3
 * @link https://docs.microsoft.com/windows/desktop/wmformat/id3-tag-support
 * @link https://github.com/brokencube/id3
 * @link http://www.zedwood.com/article/php-calculate-duration-of-mp3
 * @link https://www.mp3tag.de/en/
 * @link https://github.com/taglib/taglib/tree/master/tests
 */
final class ID3{

	private const BITRATES = [
		0b0000 => [  0,   0,   0,   0,   0],
		0b0001 => [ 32,  32,  32,  32,   8],
		0b0010 => [ 64,  48,  40,  48,  16],
		0b0011 => [ 96,  56,  48,  56,  24],
		0b0100 => [128,  64,  56,  64,  32],
		0b0101 => [160,  80,  64,  80,  40],
		0b0110 => [192,  96,  80,  96,  48],
		0b0111 => [224, 112,  96, 112,  56],
		0b1000 => [256, 128, 112, 128,  64],
		0b1001 => [288, 160, 128, 144,  80],
		0b1010 => [320, 192, 160, 160,  96],
		0b1011 => [352, 224, 192, 176, 112],
		0b1100 => [384, 256, 224, 192, 128],
		0b1101 => [416, 320, 256, 224, 144],
		0b1110 => [448, 384, 320, 256, 160],
		0b1111 => [ -1,  -1,  -1,  -1,  -1],
	];

	private const SAMPLE_RATES = [
		0b00 => [
			0b00 => 11025,
			0b01 => 12000,
			0b10 => 8000,
			0b11 => 0,
		],
		0b10 => [
			0b00 => 22050,
			0b01 => 24000,
			0b10 => 16000,
			0b11 => 0,
		],
		0b11 => [
			0b00 => 44100,
			0b01 => 48000,
			0b10 => 32000,
			0b11 => 0,
		],
	];

	/**
	 * "Xing"/"Info" identification string at 0x0D (13), 0x15 (21) or 0x24 (36)
	 */
	private const VBR_ID_STRING_POS = [
		// v2.5
		0b00 => [
			0b00 => 21, // stereo
			0b01 => 21, // jntstereo
			0b10 => 21, // dual channel
			0b11 => 21, // mono
		],
		// v2
		0b10 => [
			0b00 => 21,
			0b01 => 21,
			0b10 => 21,
			0b11 => 13,
		],
		// v1
		0b11 => [
			0b00 => 36,
			0b01 => 36,
			0b10 => 36,
			0b11 => 21,
		],
	];

	/**
	 * @var resource
	 */
	private $fh;

	/**
	 * @return void
	 */
	public function __destruct(){

		if(is_resource($this->fh)){
			fclose($this->fh); // @codeCoverageIgnore
		}

	}

	/**
	 * @throws \chillerlan\ID3Tag\ID3Exception
	 */
	public function read(string $filename):ID3Data{
		$file = realpath($filename);

		if(!$file || !file_exists($file) || !is_file($file) || !is_readable($file)){
			throw new ID3Exception(sprintf('invalid file: %s', $filename));
		}

		$data     = new ID3Data($file);
		$this->fh = fopen($file, 'rb');

		// invalid resource or 2GB limit on 32-bit
		if(!$this->fh || $data->filesize > PHP_INT_MAX){
			return $data; // @codeCoverageIgnore
		}

		// check for an ID3v1 tag
		fseek($this->fh, -128, SEEK_END);

		if(fread($this->fh, 3) === 'TAG'){
			fseek($this->fh, -256, SEEK_END);

			$properties = [
				'id3v1'     => (new ID3v1)->parse(fread($this->fh, 256)),
				'v1tagsize' => 256,
			];

			$data->setProperties($properties);
		}

		// check for an id3v2 tag
		fseek($this->fh, 0, SEEK_SET);

		if(fread($this->fh, 3) === 'ID3'){
			fseek($this->fh, 6, SEEK_SET);
			$tagsize = ID3Helpers::syncSafeInteger(unpack('N', fread($this->fh, 4))[1]);
			fseek($this->fh, 0, SEEK_SET);

			$properties = [
				'id3v2'     => $this->readID3v2Tag(fread($this->fh, $tagsize)),
				'v2tagsize' => $tagsize + 10,
			];

			$data->setProperties($properties);
		}

		$data->setProperties($this->getMP3Stats($data->filesize, $data->v1tagsize, $data->v2tagsize));

		fclose($this->fh);

		return $data;
	}

	/**
	 *
	 * @noinspection PhpUnusedLocalVariableInspection
	 */
	private function readID3v2Tag(string $rawdata):?array{

		/**
		 * 3.1. ID3v2 header
		 *
		 * The ID3v2 tag header, which should be the first information in the
		 * file, is 10 bytes as follows:
		 *
		 * ID3v2/file identifier      "ID3"
		 * ID3v2 version              $03 00
		 * ID3v2 flags                %abc00000
		 * ID3v2 size             4 * %0xxxxxxx
		 *
		 * @link http://id3.org/id3v2.3.0#ID3v2_header
		 */
		$id3version = ord(substr($rawdata, 3, 1));

		if(!in_array($id3version, [2, 3, 4], true)){
#			throw new ID3Exception('invalid id3 version');
			return null;
		}

		$flags = ord(substr($rawdata, 5, 1));

		$compression  = false;

		$exthead      = false;
		$experimental = false;

		$hasfooter    = false;


		/**
		 * a - Unsynchronisation
		 *
		 * Bit 7 in the 'ID3v2 flags' indicates whether or not
		 * unsynchronisation is used (see section 5 for details); a set bit
		 * indicates usage.
		 */
		$unsync = (bool)($flags & 0b10000000);

		if($id3version === 2){

			/**
			 * b - Compression
			 *
			 * Bit 6 is indicating whether or not compression is used;
			 * a set bit indicates usage. Since no compression scheme has been
			 * decided yet, the ID3 decoder (for now) should just ignore the entire
			 * tag if the compression bit is set.
			 */
			$compression = (bool)($flags & 0b01000000);
		}

		if($id3version === 3 || $id3version === 4){

			/**
			 * b - Extended header
			 *
			 * Bit 6 indicates whether or not the header is followed by an
			 * extended header. The extended header is described in section 3.2.
			 */
			$exthead = (bool)($flags & 0b01000000);

			/**
			 * c - Experimental indicator
			 *
			 * Bit 5 should be used as an 'experimental indicator'.
			 * This flag should always be set when the tag is in an experimental stage.
			 */
			$experimental = (bool)($flags & 0b00100000);
		}

		if($id3version === 4){

			/**
			 * d - Footer present
			 *
			 * Bit 4 indicates that a footer (section 3.4) is present at the very
			 * end of the tag. A set bit indicates the presence of a footer.
			 */
			$hasfooter = (bool)($flags & 0b00010000);
		}

		$start = 10;

		/**
		 * 3.2. ID3v2.3 extended header
		 *
		 * @link http://id3.org/id3v2.3.0#ID3v2_extended_header
		 *
		 * Extended header size   $xx xx xx xx
		 * Extended Flags         $xx xx
		 * Size of padding        $xx xx xx xx
		 */
		if($exthead){
			$extHeaderSize = ID3Helpers::syncSafeInteger(unpack('N', substr($rawdata, $start, 4))[1]);
			$start         += 4;
			// @todo (skipping the extended header for now...)
			/** @noinspection PhpUnusedLocalVariableInspection */
			$extHeader = substr($rawdata, $start, $extHeaderSize);

			$start     += $extHeaderSize;
		}

		$tagdata = substr($rawdata, $start);

		if($unsync && $id3version <= 3){
			$tagdata = ID3Helpers::unsyncString($tagdata);
		}

		$parser = __NAMESPACE__.'\\ID3v2'.$id3version;

		return (new $parser)->parse($tagdata);
	}

	/**
	 *
	 */
	private function getMP3Stats(int $filesize, int $v1Tagsize, int $v2Tagsize):array{
		$offset     = $this->getMP3FrameStart($filesize, $v1Tagsize, $v2Tagsize);
		$framecount = 0;
		$duration   = 0.0;
		$bitrate    = 0;

		if($offset === null){
			return [];
		}

		while($offset < $filesize){
			$frame = $this->parseMP3FrameHeader($offset);

			if($frame === null){
				$offset = $this->getMP3FrameStart($filesize, $v1Tagsize, $offset);

				if($offset !== null){
					continue;
				}

				break;
			}

			/**
			 * In the Info Tag, the "Xing" identification string at 0x0D (13),
			 * 0x15 (21) or 0x24 (36) (depending on MPEG layer and number of channels)
			 * of the header is replaced by "Info" in case of a CBR file.
			 *
			 * This was done to avoid CBR files to be recognized as traditional
			 * Xing VBR files by some decoders. Although the two identification
			 * strings "Xing" and "Info" are both valid, it is suggested that you
			 * keep the identification string "Xing" in case of VBR bistream
			 * in order to keep compatibility.
			 *
			 * @link http://gabriel.mp3-tech.org/mp3infotag.html
			 */
			if($framecount === 0){
				$pos = $this::VBR_ID_STRING_POS[$frame->version][$frame->channelmode] ?? 36;
				fseek($this->fh, $offset + $pos, SEEK_SET);

				if(strtolower(fread($this->fh, 4)) !== 'xing'){ // lower just in case someone thinks they're special

					return [
						'duration' => (int)round(($filesize - $v1Tagsize - $v2Tagsize) / (($frame->bitrate * 1000) / 8)),
						'bitrate'  => $frame->bitrate,
					];
				}

			}

			$duration += $frame->duration;
			$offset   += $frame->length;
			$bitrate  += $frame->bitrate;

			$framecount++;
		}

		return [
			'duration'   => (int)round($duration),
			'bitrate'    => (int)round($bitrate / $framecount),
			'framecount' => $framecount,
		];
	}

	/**
	 *
	 */
	private function getMP3FrameStart(int $filesize, int $v1Tagsize, int $offset):?int{
		fseek($this->fh, $offset, SEEK_SET);
		$size = $filesize - $v1Tagsize;

		while($offset < $size){
			$offset++;

			$byte = fread($this->fh, 1);

			if($byte === false){
				return null;
			}

			if($byte === "\xff"){
				$byte = fread($this->fh, 1);

				if($byte === "\xf3" ||$byte === "\xfa" || $byte === "\xfb"){//
					$offset = ftell($this->fh) - 2;
					fseek($this->fh, $offset, SEEK_SET);

					return $offset;
				}

			}

		}

		return null;
	}

	/**
	 *
	 */
	private function parseMP3FrameHeader(int $offset):?stdClass{
		fseek($this->fh, $offset, SEEK_SET);

		$headerBytes = fread($this->fh, 4);

		if(strlen($headerBytes) !== 4 || !($headerBytes[0] === "\xff" && (ord($headerBytes[1]) & 0xe0))){
			return null;
		}

		$b1 = ord($headerBytes[1]);
		$b2 = ord($headerBytes[2]);
		$b3 = ord($headerBytes[3]);

		$info = new stdClass;

		/**
		 * http://www.mp3-tech.org/programmer/frame_header.html
		 * AAAA AAAA  AAAB BCCD  EEEE FFGH  IIJJ KLMM
		 * A - Frame sync (all bits set)
		 * B - MPEG Audio version ID
		 * C - Layer description
		 * D - Protection bit
		 * E - Bitrate index
		 * F - Sampling rate frequency index
		 * G - Padding bit
		 * H - Private bit
		 * I - Channel Mode
		 * J - Mode extension (Only if Joint stereo)
		 * K - Copyright
		 * L - Original
		 * M - Emphasis
		 */
#		$info->sync          = (bigEndian2Int(substr($headerBytes, 0, 2)) & 0xFFE0) >> 4;
		$info->version       = ($b1 & 0x18) >> 3;         //    BB
		$info->layer         = ($b1 & 0x06) >> 1;         //      CC
#		$info->protection    = (bool)($b1 & 0x01);        //        D
		$info->bitrateIndex  = ($b2 & 0xF0) >> 4;         // EEEE
		$info->samplerate    = ($b2 & 0x0C) >> 2;         //     FF
		$info->padding       = (bool)(($b2 & 0x02) >> 1); //       G
#		$info->private       = (bool)($b2 & 0x01);        //        H
		$info->channelmode   = ($b3 & 0xC0) >> 6;         // II
#		$info->modeextension = ($b3 & 0x30) >> 4;         //   JJ
#		$info->copyright     = (bool)(($b3 & 0x08) >> 3); //     K
#		$info->original      = (bool)(($b3 & 0x04) >> 2); //      L
#		$info->emphasis      = ($b3 & 0x03);              //       MM

		if(!in_array($info->version, [0b00, 0b10, 0b11]) || !in_array($info->layer, [0b01, 0b10, 0b11])){
			return null;
		}

		$sampleRate = $this::SAMPLE_RATES[$info->version][$info->samplerate];

		if($sampleRate <= 0){
			// Invalid sample rate value
			return null;
		}

		$bitRate = 0;

		if($info->version === 0b11){
			switch($info->layer){
				case 0b11:
					$bitRate = $this::BITRATES[$info->bitrateIndex][0];
					break;
				case 0b10:
					$bitRate = $this::BITRATES[$info->bitrateIndex][1];
					break;
				case 0b01:
					$bitRate = $this::BITRATES[$info->bitrateIndex][2];
					break;
			}
		}
		else{
			switch($info->layer){
				case 0b11:
					$bitRate = $this::BITRATES[$info->bitrateIndex][3];
					break;
				case 0b10:
				case 0b01:
					$bitRate = $this::BITRATES[$info->bitrateIndex][4];
					break;
			}
		}

		if($bitRate <= 0){
			return null; // bitrate "free"
		}

		$info->bitrate = $bitRate;
		$bitRate *= 1000;

		if($info->layer === 0b11){
			$info->length = (((12 * $bitRate) / $sampleRate) + (int)$info->padding) * 4;
		}
		elseif($info->layer === 0b10 || $info->layer === 0b01){
			$info->length = ((144 * $bitRate) / $sampleRate) + (int)$info->padding;
		}

		$info->length = floor($info->length);

		if($info->length <= 0){
			return null;
		}

		$info->duration = $info->length * 8 / $bitRate;

		return $info;
	}

	/**
	 * @todo
	 */
#	public function write(iterable $data):bool{
#		return false;
#	}

}


1			<?php
2			/**
3			* Class ID3
4			*
5			* @created 22.09.2018
6			* @author smiley <[email protected]>
7			* @copyright 2018 smiley
8			* @license MIT
9			*/
10
11			namespace chillerlan\ID3Tag;
12
13			use stdClass;
14
15			use function fclose, file_exists, floor, fopen, fread, fseek, ftell, in_array, is_file,
16			is_readable, is_resource, ord, realpath, round, sprintf, strlen, strtolower, substr, unpack;
17
18			use const PHP_INT_MAX, SEEK_END, SEEK_SET;
19
20			/**
21			* @link http://id3.org/id3guide
22			* @link http://www.mp3-tech.org/
23			* @link https://en.wikipedia.org/wiki/ID3
24			* @link https://docs.microsoft.com/windows/desktop/wmformat/id3-tag-support
25			* @link https://github.com/brokencube/id3
26			* @link http://www.zedwood.com/article/php-calculate-duration-of-mp3
27			* @link https://www.mp3tag.de/en/
28			* @link https://github.com/taglib/taglib/tree/master/tests
29			*/
30			final class ID3{
31
32			private const BITRATES = [
33			0b0000 => [ 0, 0, 0, 0, 0],
34			0b0001 => [ 32, 32, 32, 32, 8],
35			0b0010 => [ 64, 48, 40, 48, 16],
36			0b0011 => [ 96, 56, 48, 56, 24],
37			0b0100 => [128, 64, 56, 64, 32],
38			0b0101 => [160, 80, 64, 80, 40],
39			0b0110 => [192, 96, 80, 96, 48],
40			0b0111 => [224, 112, 96, 112, 56],
41			0b1000 => [256, 128, 112, 128, 64],
42			0b1001 => [288, 160, 128, 144, 80],
43			0b1010 => [320, 192, 160, 160, 96],
44			0b1011 => [352, 224, 192, 176, 112],
45			0b1100 => [384, 256, 224, 192, 128],
46			0b1101 => [416, 320, 256, 224, 144],
47			0b1110 => [448, 384, 320, 256, 160],
48			0b1111 => [ -1, -1, -1, -1, -1],
49			];
50
51			private const SAMPLE_RATES = [
52			0b00 => [
53			0b00 => 11025,
54			0b01 => 12000,
55			0b10 => 8000,
56			0b11 => 0,
57			],
58			0b10 => [
59			0b00 => 22050,
60			0b01 => 24000,
61			0b10 => 16000,
62			0b11 => 0,
63			],
64			0b11 => [
65			0b00 => 44100,
66			0b01 => 48000,
67			0b10 => 32000,
68			0b11 => 0,
69			],
70			];
71
72			/**
73			* "Xing"/"Info" identification string at 0x0D (13), 0x15 (21) or 0x24 (36)
74			*/
75			private const VBR_ID_STRING_POS = [
76			// v2.5
77			0b00 => [
78			0b00 => 21, // stereo
79			0b01 => 21, // jntstereo
80			0b10 => 21, // dual channel
81			0b11 => 21, // mono
82			],
83			// v2
84			0b10 => [
85			0b00 => 21,
86			0b01 => 21,
87			0b10 => 21,
88			0b11 => 13,
89			],
90			// v1
91			0b11 => [
92			0b00 => 36,
93			0b01 => 36,
94			0b10 => 36,
95			0b11 => 21,
96			],
97			];
98
99			/**
100			* @var resource
101			*/
102			private $fh;
103
104			/**
105			* @return void
106			*/
107			public function __destruct(){
108
109			if(is_resource($this->fh)){
110			fclose($this->fh); // @codeCoverageIgnore
111			}
112
113			}
114
115			/**
116			* @throws \chillerlan\ID3Tag\ID3Exception
117			*/
118			public function read(string $filename):ID3Data{
119			$file = realpath($filename);
120
121			if(!$file \|\| !file_exists($file) \|\| !is_file($file) \|\| !is_readable($file)){
122			throw new ID3Exception(sprintf('invalid file: %s', $filename));
123			}
124
125			$data = new ID3Data($file);
126			$this->fh = fopen($file, 'rb');
127
128			// invalid resource or 2GB limit on 32-bit
129			if(!$this->fh \|\| $data->filesize > PHP_INT_MAX){
130			return $data; // @codeCoverageIgnore
131			}
132
133			// check for an ID3v1 tag
134			fseek($this->fh, -128, SEEK_END);
135
136			if(fread($this->fh, 3) === 'TAG'){
137			fseek($this->fh, -256, SEEK_END);
138
139			$properties = [
140			'id3v1' => (new ID3v1)->parse(fread($this->fh, 256)),
141			'v1tagsize' => 256,
142			];
143
144			$data->setProperties($properties);
145			}
146
147			// check for an id3v2 tag
148			fseek($this->fh, 0, SEEK_SET);
149
150			if(fread($this->fh, 3) === 'ID3'){
151			fseek($this->fh, 6, SEEK_SET);
152			$tagsize = ID3Helpers::syncSafeInteger(unpack('N', fread($this->fh, 4))[1]);
153			fseek($this->fh, 0, SEEK_SET);
154
155			$properties = [
156			'id3v2' => $this->readID3v2Tag(fread($this->fh, $tagsize)),
157			'v2tagsize' => $tagsize + 10,
158			];
159
160			$data->setProperties($properties);
161			}
162
163			$data->setProperties($this->getMP3Stats($data->filesize, $data->v1tagsize, $data->v2tagsize));
164
165			fclose($this->fh);
166
167			return $data;
168			}
169
170			/**
171			*
172			* @noinspection PhpUnusedLocalVariableInspection
173			*/
174			private function readID3v2Tag(string $rawdata):?array{
175
176			/**
177			* 3.1. ID3v2 header
178			*
179			* The ID3v2 tag header, which should be the first information in the
180			* file, is 10 bytes as follows:
181			*
182			* ID3v2/file identifier "ID3"
183			* ID3v2 version $03 00
184			* ID3v2 flags %abc00000
185			* ID3v2 size 4 * %0xxxxxxx
186			*
187			* @link http://id3.org/id3v2.3.0#ID3v2_header
188			*/
189			$id3version = ord(substr($rawdata, 3, 1));
190
191			if(!in_array($id3version, [2, 3, 4], true)){
192			# throw new ID3Exception('invalid id3 version');
193			return null;
194			}
195
196			$flags = ord(substr($rawdata, 5, 1));
197
198			$compression = false;
			0 ignored issues – show Unused Code introduced 2021-05-08 22:35 UTC by Report Bug Copy Issue Report The assignment to `$compression` is dead and can be removed. Loading history...
199			$exthead = false;
200			$experimental = false;
			0 ignored issues – show Unused Code introduced 2021-05-08 22:35 UTC by Report Bug Copy Issue Report The assignment to `$experimental` is dead and can be removed. Loading history...
201			$hasfooter = false;
			0 ignored issues – show Unused Code introduced 2021-05-08 22:35 UTC by Report Bug Copy Issue Report The assignment to `$hasfooter` is dead and can be removed. Loading history...
202
203			/**
204			* a - Unsynchronisation
205			*
206			* Bit 7 in the 'ID3v2 flags' indicates whether or not
207			* unsynchronisation is used (see section 5 for details); a set bit
208			* indicates usage.
209			*/
210			$unsync = (bool)($flags & 0b10000000);
211
212			if($id3version === 2){
213
214			/**
215			* b - Compression
216			*
217			* Bit 6 is indicating whether or not compression is used;
218			* a set bit indicates usage. Since no compression scheme has been
219			* decided yet, the ID3 decoder (for now) should just ignore the entire
220			* tag if the compression bit is set.
221			*/
222			$compression = (bool)($flags & 0b01000000);
223			}
224
225			if($id3version === 3 \|\| $id3version === 4){
226
227			/**
228			* b - Extended header
229			*
230			* Bit 6 indicates whether or not the header is followed by an
231			* extended header. The extended header is described in section 3.2.
232			*/
233			$exthead = (bool)($flags & 0b01000000);
234
235			/**
236			* c - Experimental indicator
237			*
238			* Bit 5 should be used as an 'experimental indicator'.
239			* This flag should always be set when the tag is in an experimental stage.
240			*/
241			$experimental = (bool)($flags & 0b00100000);
242			}
243
244			if($id3version === 4){
245
246			/**
247			* d - Footer present
248			*
249			* Bit 4 indicates that a footer (section 3.4) is present at the very
250			* end of the tag. A set bit indicates the presence of a footer.
251			*/
252			$hasfooter = (bool)($flags & 0b00010000);
253			}
254
255			$start = 10;
256
257			/**
258			* 3.2. ID3v2.3 extended header
259			*
260			* @link http://id3.org/id3v2.3.0#ID3v2_extended_header
261			*
262			* Extended header size $xx xx xx xx
263			* Extended Flags $xx xx
264			* Size of padding $xx xx xx xx
265			*/
266			if($exthead){
267			$extHeaderSize = ID3Helpers::syncSafeInteger(unpack('N', substr($rawdata, $start, 4))[1]);
268			$start += 4;
269			// @todo (skipping the extended header for now...)
270			/** @noinspection PhpUnusedLocalVariableInspection */
271			$extHeader = substr($rawdata, $start, $extHeaderSize);
			0 ignored issues – show Unused Code introduced 2021-05-08 22:35 UTC by Report Bug Copy Issue Report The assignment to `$extHeader` is dead and can be removed. Loading history...
272			$start += $extHeaderSize;
273			}
274
275			$tagdata = substr($rawdata, $start);
276
277			if($unsync && $id3version <= 3){
278			$tagdata = ID3Helpers::unsyncString($tagdata);
279			}
280
281			$parser = __NAMESPACE__.'\\ID3v2'.$id3version;
282
283			return (new $parser)->parse($tagdata);
284			}
285
286			/**
287			*
288			*/
289			private function getMP3Stats(int $filesize, int $v1Tagsize, int $v2Tagsize):array{
290			$offset = $this->getMP3FrameStart($filesize, $v1Tagsize, $v2Tagsize);
291			$framecount = 0;
292			$duration = 0.0;
293			$bitrate = 0;
294
295			if($offset === null){
296			return [];
297			}
298
299			while($offset < $filesize){
300			$frame = $this->parseMP3FrameHeader($offset);
301
302			if($frame === null){
303			$offset = $this->getMP3FrameStart($filesize, $v1Tagsize, $offset);
304
305			if($offset !== null){
306			continue;
307			}
308
309			break;
310			}
311
312			/**
313			* In the Info Tag, the "Xing" identification string at 0x0D (13),
314			* 0x15 (21) or 0x24 (36) (depending on MPEG layer and number of channels)
315			* of the header is replaced by "Info" in case of a CBR file.
316			*
317			* This was done to avoid CBR files to be recognized as traditional
318			* Xing VBR files by some decoders. Although the two identification
319			* strings "Xing" and "Info" are both valid, it is suggested that you
320			* keep the identification string "Xing" in case of VBR bistream
321			* in order to keep compatibility.
322			*
323			* @link http://gabriel.mp3-tech.org/mp3infotag.html
324			*/
325			if($framecount === 0){
326			$pos = $this::VBR_ID_STRING_POS[$frame->version][$frame->channelmode] ?? 36;
327			fseek($this->fh, $offset + $pos, SEEK_SET);
328
329			if(strtolower(fread($this->fh, 4)) !== 'xing'){ // lower just in case someone thinks they're special
330
331			return [
332			'duration' => (int)round(($filesize - $v1Tagsize - $v2Tagsize) / (($frame->bitrate * 1000) / 8)),
333			'bitrate' => $frame->bitrate,
334			];
335			}
336
337			}
338
339			$duration += $frame->duration;
340			$offset += $frame->length;
341			$bitrate += $frame->bitrate;
342
343			$framecount++;
344			}
345
346			return [
347			'duration' => (int)round($duration),
348			'bitrate' => (int)round($bitrate / $framecount),
349			'framecount' => $framecount,
350			];
351			}
352
353			/**
354			*
355			*/
356			private function getMP3FrameStart(int $filesize, int $v1Tagsize, int $offset):?int{
357			fseek($this->fh, $offset, SEEK_SET);
358			$size = $filesize - $v1Tagsize;
359
360			while($offset < $size){
361			$offset++;
362
363			$byte = fread($this->fh, 1);
364
365			if($byte === false){
366			return null;
367			}
368
369			if($byte === "\xff"){
370			$byte = fread($this->fh, 1);
371
372			if($byte === "\xf3" \|\|$byte === "\xfa" \|\| $byte === "\xfb"){//
373			$offset = ftell($this->fh) - 2;
374			fseek($this->fh, $offset, SEEK_SET);
375
376			return $offset;
377			}
378
379			}
380
381			}
382
383			return null;
384			}
385
386			/**
387			*
388			*/
389			private function parseMP3FrameHeader(int $offset):?stdClass{
390			fseek($this->fh, $offset, SEEK_SET);
391
392			$headerBytes = fread($this->fh, 4);
393
394			if(strlen($headerBytes) !== 4 \|\| !($headerBytes[0] === "\xff" && (ord($headerBytes[1]) & 0xe0))){
395			return null;
396			}
397
398			$b1 = ord($headerBytes[1]);
399			$b2 = ord($headerBytes[2]);
400			$b3 = ord($headerBytes[3]);
401
402			$info = new stdClass;
403
404			/**
405			* http://www.mp3-tech.org/programmer/frame_header.html
406			* AAAA AAAA AAAB BCCD EEEE FFGH IIJJ KLMM
407			* A - Frame sync (all bits set)
408			* B - MPEG Audio version ID
409			* C - Layer description
410			* D - Protection bit
411			* E - Bitrate index
412			* F - Sampling rate frequency index
413			* G - Padding bit
414			* H - Private bit
415			* I - Channel Mode
416			* J - Mode extension (Only if Joint stereo)
417			* K - Copyright
418			* L - Original
419			* M - Emphasis
420			*/
421			# $info->sync = (bigEndian2Int(substr($headerBytes, 0, 2)) & 0xFFE0) >> 4;
422			$info->version = ($b1 & 0x18) >> 3; // BB
423			$info->layer = ($b1 & 0x06) >> 1; // CC
424			# $info->protection = (bool)($b1 & 0x01); // D
425			$info->bitrateIndex = ($b2 & 0xF0) >> 4; // EEEE
426			$info->samplerate = ($b2 & 0x0C) >> 2; // FF
427			$info->padding = (bool)(($b2 & 0x02) >> 1); // G
428			# $info->private = (bool)($b2 & 0x01); // H
429			$info->channelmode = ($b3 & 0xC0) >> 6; // II
430			# $info->modeextension = ($b3 & 0x30) >> 4; // JJ
431			# $info->copyright = (bool)(($b3 & 0x08) >> 3); // K
432			# $info->original = (bool)(($b3 & 0x04) >> 2); // L
433			# $info->emphasis = ($b3 & 0x03); // MM
434
435			if(!in_array($info->version, [0b00, 0b10, 0b11]) \|\| !in_array($info->layer, [0b01, 0b10, 0b11])){
436			return null;
437			}
438
439			$sampleRate = $this::SAMPLE_RATES[$info->version][$info->samplerate];
440
441			if($sampleRate <= 0){
442			// Invalid sample rate value
443			return null;
444			}
445
446			$bitRate = 0;
447
448			if($info->version === 0b11){
449			switch($info->layer){
450			case 0b11:
451			$bitRate = $this::BITRATES[$info->bitrateIndex][0];
452			break;
453			case 0b10:
454			$bitRate = $this::BITRATES[$info->bitrateIndex][1];
455			break;
456			case 0b01:
457			$bitRate = $this::BITRATES[$info->bitrateIndex][2];
458			break;
459			}
460			}
461			else{
462			switch($info->layer){
463			case 0b11:
464			$bitRate = $this::BITRATES[$info->bitrateIndex][3];
465			break;
466			case 0b10:
467			case 0b01:
468			$bitRate = $this::BITRATES[$info->bitrateIndex][4];
469			break;
470			}
471			}
472
473			if($bitRate <= 0){
474			return null; // bitrate "free"
475			}
476
477			$info->bitrate = $bitRate;
478			$bitRate *= 1000;
479
480			if($info->layer === 0b11){
481			$info->length = (((12 * $bitRate) / $sampleRate) + (int)$info->padding) * 4;
482			}
483			elseif($info->layer === 0b10 \|\| $info->layer === 0b01){
484			$info->length = ((144 * $bitRate) / $sampleRate) + (int)$info->padding;
485			}
486
487			$info->length = floor($info->length);
488
489			if($info->length <= 0){
490			return null;
491			}
492
493			$info->duration = $info->length * 8 / $bitRate;
494
495			return $info;
496			}
497
498			/**
499			* @todo
500			*/
501			# public function write(iterable $data):bool{
502			# return false;
503			# }
504
505			}
506

chillerlan / php-id3tag

ID3::parseMP3FrameHeader() D last analyzed 2021-05-10 10:21 UTC

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ID3::parseMP3FrameHeader() D
last analyzed 2021-05-10 10:21 UTC