getid3_mp3::FreeFormatFrameLength

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Syntax Syntax

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

Parameters Parameters

$offset

(int) (Required)

$deepscan

(bool) (Optional)

Default value: false

Return Return

(int|false)

Source Source

File: wp-includes/ID3/module.audio.mp3.php

				return false;
			}
		}
		return true;
	}

	/**
	 * @param int  $offset
	 * @param bool $deepscan
	 *
	 * @return int|false
	 */
	public function FreeFormatFrameLength($offset, $deepscan=false) {
		$info = &$this->getid3->info;

		$this->fseek($offset);
		$MPEGaudioData = $this->fread(32768);

		$SyncPattern1 = substr($MPEGaudioData, 0, 4);
		// may be different pattern due to padding
		$SyncPattern2 = $SyncPattern1[0].$SyncPattern1[1].chr(ord($SyncPattern1[2]) | 0x02).$SyncPattern1[3];
		if ($SyncPattern2 === $SyncPattern1) {
			$SyncPattern2 = $SyncPattern1[0].$SyncPattern1[1].chr(ord($SyncPattern1[2]) & 0xFD).$SyncPattern1[3];
		}

		$framelength = false;
		$framelength1 = strpos($MPEGaudioData, $SyncPattern1, 4);
		$framelength2 = strpos($MPEGaudioData, $SyncPattern2, 4);
		if ($framelength1 > 4) {
			$framelength = $framelength1;
		}
		if (($framelength2 > 4) && ($framelength2 < $framelength1)) {
			$framelength = $framelength2;
		}
		if (!$framelength) {

			// LAME 3.88 has a different value for modeextension on the first frame vs the rest
			$framelength1 = strpos($MPEGaudioData, substr($SyncPattern1, 0, 3), 4);
			$framelength2 = strpos($MPEGaudioData, substr($SyncPattern2, 0, 3), 4);

			if ($framelength1 > 4) {
				$framelength = $framelength1;
			}
			if (($framelength2 > 4) && ($framelength2 < $framelength1)) {
				$framelength = $framelength2;
			}
			if (!$framelength) {
				$this->error('Cannot find next free-format synch pattern ('.getid3_lib::PrintHexBytes($SyncPattern1).' or '.getid3_lib::PrintHexBytes($SyncPattern2).') after offset '.$offset);
				return false;
			} else {
				$this->warning('ModeExtension varies between first frame and other frames (known free-format issue in LAME 3.88)');
				$info['audio']['codec']   = 'LAME';
				$info['audio']['encoder'] = 'LAME3.88';
				$SyncPattern1 = substr($SyncPattern1, 0, 3);
				$SyncPattern2 = substr($SyncPattern2, 0, 3);
			}
		}

		if ($deepscan) {

			$ActualFrameLengthValues = array();
			$nextoffset = $offset + $framelength;
			while ($nextoffset < ($info['avdataend'] - 6)) {
				$this->fseek($nextoffset - 1);
				$NextSyncPattern = $this->fread(6);
				if ((substr($NextSyncPattern, 1, strlen($SyncPattern1)) == $SyncPattern1) || (substr($NextSyncPattern, 1, strlen($SyncPattern2)) == $SyncPattern2)) {
					// good - found where expected
					$ActualFrameLengthValues[] = $framelength;
				} elseif ((substr($NextSyncPattern, 0, strlen($SyncPattern1)) == $SyncPattern1) || (substr($NextSyncPattern, 0, strlen($SyncPattern2)) == $SyncPattern2)) {
					// ok - found one byte earlier than expected (last frame wasn't padded, first frame was)
					$ActualFrameLengthValues[] = ($framelength - 1);
					$nextoffset--;
				} elseif ((substr($NextSyncPattern, 2, strlen($SyncPattern1)) == $SyncPattern1) || (substr($NextSyncPattern, 2, strlen($SyncPattern2)) == $SyncPattern2)) {
					// ok - found one byte later than expected (last frame was padded, first frame wasn't)
					$ActualFrameLengthValues[] = ($framelength + 1);
					$nextoffset++;

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