module.audio-video.mpeg.php

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		//But in MPEG-2, this header must immediately be followed by an
		//extension_start_code (0x000001B5) with a sequence_extension ID (1).
		//(This extension contains all the additional MPEG-2 stuff.)
		//MPEG-1 doesn't have this extension, so that's a sure way to tell the
		//difference between MPEG-1 and MPEG-2 video streams.

		if (substr($MPEGstreamData, $VideoChunkOffset, 4) == GETID3_MPEG_VIDEO_EXTENSION_START) {
			$ThisFileInfo['video']['codec'] = 'MPEG-2';
		} else {
			$ThisFileInfo['video']['codec'] = 'MPEG-1';
		}


		$AudioChunkOffset = 0;
		while (true) {
			while (substr($MPEGstreamData, $AudioChunkOffset++, 4) !== GETID3_MPEG_AUDIO_START) {
				if ($AudioChunkOffset >= $MPEGstreamDataLength) {
					break 2;
				}
			}

			for ($i = 0; $i <= 7; $i++) {
				// some files have the MPEG-audio header 8 bytes after the end of the $00 $00 $01 $C0 signature, some have it up to 13 bytes (or more?) after
				// I have no idea why or what the difference is, so this is a stupid hack.
				// If anybody has any better idea of what's going on, please let me know - [e-mail]

				$dummy = $ThisFileInfo;
				if (getid3_mp3::decodeMPEGaudioHeader($fd, ($AudioChunkOffset + 3) + 8 + $i, $dummy, false)) {
					$ThisFileInfo = $dummy;
					$ThisFileInfo['audio']['bitrate_mode']    = 'cbr';
					$ThisFileInfo['audio']['lossless']        = false;
					break 2;

				}
			}
		}

		// Temporary hack to account for interleaving overhead:
		if (!empty($ThisFileInfo['video']['bitrate']) && !empty($ThisFileInfo['audio']['bitrate'])) {
			$ThisFileInfo['playtime_seconds'] = (($ThisFileInfo['avdataend'] - $ThisFileInfo['avdataoffset']) * 8) / ($ThisFileInfo['video']['bitrate'] + $ThisFileInfo['audio']['bitrate']);

			// Interleaved MPEG audio/video files have a certain amount of overhead that varies
			// by both video and audio bitrates, and not in any sensible, linear/logarithmic patter
			// Use interpolated lookup tables to approximately guess how much is overhead, because
			// playtime is calculated as filesize / total-bitrate
			$ThisFileInfo['playtime_seconds'] *= $this->MPEGsystemNonOverheadPercentage($ThisFileInfo['video']['bitrate'], $ThisFileInfo['audio']['bitrate']);

			//switch ($ThisFileInfo['video']['bitrate']) {
			//	case('5000000'):
			//		$multiplier = 0.93292642112380355828048824319889;
			//		break;
			//	case('5500000'):
			//		$multiplier = 0.93582895375200989965359777343219;
			//		break;
			//	case('6000000'):
			//		$multiplier = 0.93796247714820932532911373859139;
			//		break;
			//	case('7000000'):
			//		$multiplier = 0.9413264083635103463010117778776;
			//		break;
			//	default:
			//		$multiplier = 1;
			//		break;
			//}
			//$ThisFileInfo['playtime_seconds'] *= $multiplier;
			//$ThisFileInfo['warning'][] = 'Interleaved MPEG audio/video playtime may be inaccurate. With current hack should be within a few seconds of accurate. Report to [e-mail] if off by more than 10 seconds.';
			if ($ThisFileInfo['video']['bitrate'] < 50000) {
				$ThisFileInfo['warning'][] = 'Interleaved MPEG audio/video playtime may be slightly inaccurate for video bitrates below 100kbps. Except in extreme low-bitrate situations, error should be less than 1%. Report to [e-mail] if greater than this.';
			}
		}

		return true;
	}


	function MPEGsystemNonOverheadPercentage($VideoBitrate, $AudioBitrate) {
		$OverheadPercentage = 0;

		$AudioBitrate = max(min($AudioBitrate / 1000,   384), 32); // limit to range of 32kbps - 384kbps (should be only legal bitrates, but maybe VBR?)
		$VideoBitrate = max(min($VideoBitrate / 1000, 10000), 10); // limit to range of 10kbps -  10Mbps (beyond that curves flatten anyways, no big loss)


		//OMBB[audiobitrate]              = array(video-10kbps,       video-100kbps,      video-1000kbps,     video-10000kbps)
		$OverheadMultiplierByBitrate[32]  = array(0, 0.9676287944368530, 0.9802276264360310, 0.9844916183244460, 0.9852821845179940);
		$OverheadMultiplierByBitrate[48]  = array(0, 0.9779100089209830, 0.9787770035359320, 0.9846738664076130, 0.9852683013799960);
		$OverheadMultiplierByBitrate[56]  = array(0, 0.9731249855367600, 0.9776624308938040, 0.9832606361852130, 0.9843922606633340);
		$OverheadMultiplierByBitrate[64]  = array(0, 0.9755642683275760, 0.9795256705493390, 0.9836573009193170, 0.9851122539404470);
		$OverheadMultiplierByBitrate[96]  = array(0, 0.9788025247497290, 0.9798553314148700, 0.9822956869792560, 0.9834815119124690);
		$OverheadMultiplierByBitrate[128] = array(0, 0.9816940050925480, 0.9821675936072120, 0.9829756927470870, 0.9839763420152050);
		$OverheadMultiplierByBitrate[160] = array(0, 0.9825894094561180, 0.9820913399073960, 0.9823907143253970, 0.9832821783651570);
		$OverheadMultiplierByBitrate[192] = array(0, 0.9832038474336260, 0.9825731694317960, 0.9821028622712400, 0.9828262076447620);
		$OverheadMultiplierByBitrate[224] = array(0, 0.9836516298538770, 0.9824718601823890, 0.9818302180625380, 0.9823735101626480);
		$OverheadMultiplierByBitrate[256] = array(0, 0.9845863022094920, 0.9837229411967540, 0.9824521662210830, 0.9828645172100790);
		$OverheadMultiplierByBitrate[320] = array(0, 0.9849565280263180, 0.9837683142805110, 0.9822885275960400, 0.9824424382727190);
		$OverheadMultiplierByBitrate[384] = array(0, 0.9856094774357600, 0.9844573394432720, 0.9825970399837330, 0.9824673808303890);

		$BitrateToUseMin = 32;
		$BitrateToUseMax = 32;
		$previousBitrate = 32;
		foreach ($OverheadMultiplierByBitrate as $key => $value) {
			if ($AudioBitrate >= $previousBitrate) {
				$BitrateToUseMin = $previousBitrate;
			}
			if ($AudioBitrate < $key) {
				$BitrateToUseMax = $key;
				break;
			}
			$previousBitrate = $key;
		}
		$FactorA = ($BitrateToUseMax - $AudioBitrate) / ($BitrateToUseMax - $BitrateToUseMin);

		$VideoBitrateLog10 = log10($VideoBitrate);
		$VideoFactorMin1 = $OverheadMultiplierByBitrate[$BitrateToUseMin][floor($VideoBitrateLog10)];
		$VideoFactorMin2 = $OverheadMultiplierByBitrate[$BitrateToUseMax][floor($VideoBitrateLog10)];
		$VideoFactorMax1 = $OverheadMultiplierByBitrate[$BitrateToUseMin][ceil($VideoBitrateLog10)];
		$VideoFactorMax2 = $OverheadMultiplierByBitrate[$BitrateToUseMax][ceil($VideoBitrateLog10)];
		$FactorV = $VideoBitrateLog10 - floor($VideoBitrateLog10);

		$OverheadPercentage  = $VideoFactorMin1 *      $FactorA  *      $FactorV;
		$OverheadPercentage += $VideoFactorMin2 * (1 - $FactorA) *      $FactorV;
		$OverheadPercentage += $VideoFactorMax1 *      $FactorA  * (1 - $FactorV);
		$OverheadPercentage += $VideoFactorMax2 * (1 - $FactorA) * (1 - $FactorV);

		return $OverheadPercentage;
	}


	function MPEGvideoFramerateLookup($rawframerate) {
		$MPEGvideoFramerateLookup = array(0, 23.976, 24, 25, 29.97, 30, 50, 59.94, 60);
		return (isset($MPEGvideoFramerateLookup[$rawframerate]) ? (float) $MPEGvideoFramerateLookup[$rawframerate] : (float) 0);
	}

	function MPEGvideoAspectRatioLookup($rawaspectratio) {
		$MPEGvideoAspectRatioLookup = array(0, 1, 0.6735, 0.7031, 0.7615, 0.8055, 0.8437, 0.8935, 0.9157, 0.9815, 1.0255, 1.0695, 1.0950, 1.1575, 1.2015, 0);
		return (isset($MPEGvideoAspectRatioLookup[$rawaspectratio]) ? (float) $MPEGvideoAspectRatioLookup[$rawaspectratio] : (float) 0);
	}

	function MPEGvideoAspectRatioTextLookup($rawaspectratio) {
		$MPEGvideoAspectRatioTextLookup = array('forbidden', 'square pixels', '0.6735', '16:9, 625 line, PAL', '0.7615', '0.8055', '16:9, 525 line, NTSC', '0.8935', '4:3, 625 line, PAL, CCIR601', '0.9815', '1.0255', '1.0695', '4:3, 525 line, NTSC, CCIR601', '1.1575', '1.2015', 'reserved');
		return (isset($MPEGvideoAspectRatioTextLookup[$rawaspectratio]) ? $MPEGvideoAspectRatioTextLookup[$rawaspectratio] : '');
	}

}


?>