getID3::CalculateCompressionRatioVideo

	public function ChannelsBitratePlaytimeCalculations() {

		// set channelmode on audio
		if (!empty($this->info['audio']['channelmode']) || !isset($this->info['audio']['channels'])) {
			// ignore
		} elseif ($this->info['audio']['channels'] == 1) {
			$this->info['audio']['channelmode'] = 'mono';
		} elseif ($this->info['audio']['channels'] == 2) {
			$this->info['audio']['channelmode'] = 'stereo';
		}

		// Calculate combined bitrate - audio + video
		$CombinedBitrate  = 0;
		$CombinedBitrate += (isset($this->info['audio']['bitrate']) ? $this->info['audio']['bitrate'] : 0);
		$CombinedBitrate += (isset($this->info['video']['bitrate']) ? $this->info['video']['bitrate'] : 0);
		if (($CombinedBitrate > 0) && empty($this->info['bitrate'])) {
			$this->info['bitrate'] = $CombinedBitrate;
		}
		//if ((isset($this->info['video']) && !isset($this->info['video']['bitrate'])) || (isset($this->info['audio']) && !isset($this->info['audio']['bitrate']))) {
		//	// for example, VBR MPEG video files cannot determine video bitrate:
		//	// should not set overall bitrate and playtime from audio bitrate only
		//	unset($this->info['bitrate']);
		//}

		// video bitrate undetermined, but calculable
		if (isset($this->info['video']['dataformat']) && $this->info['video']['dataformat'] && (!isset($this->info['video']['bitrate']) || ($this->info['video']['bitrate'] == 0))) {
			// if video bitrate not set
			if (isset($this->info['audio']['bitrate']) && ($this->info['audio']['bitrate'] > 0) && ($this->info['audio']['bitrate'] == $this->info['bitrate'])) {
				// AND if audio bitrate is set to same as overall bitrate
				if (isset($this->info['playtime_seconds']) && ($this->info['playtime_seconds'] > 0)) {
					// AND if playtime is set
					if (isset($this->info['avdataend']) && isset($this->info['avdataoffset'])) {
						// AND if AV data offset start/end is known
						// THEN we can calculate the video bitrate
						$this->info['bitrate'] = round((($this->info['avdataend'] - $this->info['avdataoffset']) * 8) / $this->info['playtime_seconds']);
						$this->info['video']['bitrate'] = $this->info['bitrate'] - $this->info['audio']['bitrate'];
					}
				}
			}
		}

		if ((!isset($this->info['playtime_seconds']) || ($this->info['playtime_seconds'] <= 0)) && !empty($this->info['bitrate'])) {
			$this->info['playtime_seconds'] = (($this->info['avdataend'] - $this->info['avdataoffset']) * 8) / $this->info['bitrate'];
		}

		if (!isset($this->info['bitrate']) && !empty($this->info['playtime_seconds'])) {