protected function leadMP4()
	{
		$lead = $this->ffprobeFormat("mp4", "m4a");

		if ($lead === true)
		{
			if ($this->ffprobeHasVideo() !== false)
			{
				return $this->closeCase("mp4", "video/mp4", $this->metadata);
			}
			else if ($this->ffprobeHasAudio() !== false)
			{
				return $this->closeCase("mp4", "audio/mp4", $this->metadata);
			}
			else
			{
				return false;
			}
		}

		return null;
	}