getid3_mp3::FreeFormatFrameLength( int $offset, bool $deepscan = false ): int|false

Compatibility

Present in every tracked release (6.7.7 to 7.1.0), and compiles on PHP 7.4 through 8.6-dev.

Parameters

$offsetint

$deepscanbooloptional

Default: false

Return value

int|false

Performance profile

How much work a call to getid3_mp3::FreeFormatFrameLength() does, and what it touches: the algorithmic scaling, the Zend instruction count per call across PHP versions, the hooks it hands control to, and the core code that calls it. Measured from the compiled opcodes, not a stopwatch, so every number is identical on any machine running the same PHP version, and every function in core is ranked by cost.

Cost class

Light

Touches nothing outside its own arguments.

Scaling

Scales with input

The body loops, so the work grows with what you pass in.

Instructions

42–142

Executed per call on PHP 8.5, depending on the branch taken. The body compiles to 184.

Plugin surface

None

Nothing here hands control to plugin code.

Called by

1

1 place in core call this, so the cost is paid more often than your own code shows.

What one call costs · 14 distinct outcomes

One number would be a lie: the work depends on which branch runs. These are every distinct cost getid3_mp3::FreeFormatFrameLength() can have, taken from its control-flow graph on PHP 8.5.

Uses · 5

• getid3_mp3::fseek()
• getid3_mp3::fread()
• getid3_mp3::error()
• getid3_lib::PrintHexBytes()
• getid3_mp3::warning()

Used by · 1

• getid3_mp3::decodeMPEGaudioHeader()

Source code

View on Trac ↗View on GitHub ↗

1220	public function FreeFormatFrameLength($offset, $deepscan=false) {1221		$info = &$this->getid3->info;1222 1223		$this->fseek($offset);1224		$MPEGaudioData = $this->fread(32768);1225 1226		$SyncPattern1 = substr($MPEGaudioData, 0, 4);1227		// may be different pattern due to padding1228		$SyncPattern2 = $SyncPattern1[0].$SyncPattern1[1].chr(ord($SyncPattern1[2]) | 0x02).$SyncPattern1[3];1229		if ($SyncPattern2 === $SyncPattern1) {1230			$SyncPattern2 = $SyncPattern1[0].$SyncPattern1[1].chr(ord($SyncPattern1[2]) & 0xFD).$SyncPattern1[3];1231		}1232 1233		$framelength = false;1234		$framelength1 = strpos($MPEGaudioData, $SyncPattern1, 4);1235		$framelength2 = strpos($MPEGaudioData, $SyncPattern2, 4);1236		if ($framelength1 > 4) {1237			$framelength = $framelength1;1238		}1239		if (($framelength2 > 4) && ($framelength2 < $framelength1)) {1240			$framelength = $framelength2;1241		}1242		if (!$framelength) {1243 1244			// LAME 3.88 has a different value for modeextension on the first frame vs the rest1245			$framelength1 = strpos($MPEGaudioData, substr($SyncPattern1, 0, 3), 4);1246			$framelength2 = strpos($MPEGaudioData, substr($SyncPattern2, 0, 3), 4);1247 1248			if ($framelength1 > 4) {1249				$framelength = $framelength1;1250			}1251			if (($framelength2 > 4) && ($framelength2 < $framelength1)) {1252				$framelength = $framelength2;1253			}1254			if (!$framelength) {1255				$this->error('Cannot find next free-format synch pattern ('.getid3_lib::PrintHexBytes($SyncPattern1).' or '.getid3_lib::PrintHexBytes($SyncPattern2).') after offset '.$offset);1256				return false;1257			} else {1258				$this->warning('ModeExtension varies between first frame and other frames (known free-format issue in LAME 3.88)');1259				$info['audio']['codec']   = 'LAME';1260				$info['audio']['encoder'] = 'LAME3.88';1261				$SyncPattern1 = substr($SyncPattern1, 0, 3);1262				$SyncPattern2 = substr($SyncPattern2, 0, 3);1263			}1264		}1265 1266		if ($deepscan) {1267 1268			$ActualFrameLengthValues = array();1269			$nextoffset = $offset + $framelength;1270			while ($nextoffset < ($info['avdataend'] - 6)) {1271				$this->fseek($nextoffset - 1);1272				$NextSyncPattern = $this->fread(6);1273				if ((substr($NextSyncPattern, 1, strlen($SyncPattern1)) == $SyncPattern1) || (substr($NextSyncPattern, 1, strlen($SyncPattern2)) == $SyncPattern2)) {1274					// good - found where expected1275					$ActualFrameLengthValues[] = $framelength;1276				} elseif ((substr($NextSyncPattern, 0, strlen($SyncPattern1)) == $SyncPattern1) || (substr($NextSyncPattern, 0, strlen($SyncPattern2)) == $SyncPattern2)) {1277					// ok - found one byte earlier than expected (last frame wasn't padded, first frame was)1278					$ActualFrameLengthValues[] = ($framelength - 1);1279					$nextoffset--;1280				} elseif ((substr($NextSyncPattern, 2, strlen($SyncPattern1)) == $SyncPattern1) || (substr($NextSyncPattern, 2, strlen($SyncPattern2)) == $SyncPattern2)) {1281					// ok - found one byte later than expected (last frame was padded, first frame wasn't)1282					$ActualFrameLengthValues[] = ($framelength + 1);1283					$nextoffset++;1284				} else {1285					$this->error('Did not find expected free-format sync pattern at offset '.$nextoffset);1286					return false;1287				}1288				$nextoffset += $framelength;1289			}1290			if (count($ActualFrameLengthValues) > 0) {1291				$framelength = intval(round(array_sum($ActualFrameLengthValues) / count($ActualFrameLengthValues)));1292			}1293		}1294		return $framelength;1295	}

Changelog

Unchanged from 6.7.7 through 7.1.0.

1. 6.7.7
2. 6.8.8
3. 6.9.7
4. 7.0.4
5. 7.1.0

Signature, return type and hooks compared across 5 parsed releases.

About this page

Parsed data

Generated from the wordpress-develop 7.1.0 tag, from src/wp-includes/ID3/module.audio.mp3.php, and regenerated for each WordPress release so it tracks the code rather than a snapshot of it.

Corrections

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