I am new to all this and don't understand everything yet. In tmpg there is 4 different modes to encode that I am unclear on. Audio,Video,System Audio, System Video. What is the difference between "Audio" and "System Audio"?? And likewise, the difference between. "Video" and "System Video"? And I am confused on the difference between "Multiplex" and "Simple Multiplex" Same for the "Demultiplex" and "Simple Multiplex"