Adding a TV tuner requires a different FBAS control head. If you look at the TV uner module, it has 4 antenna connections and the a green fakra out. This is what sends video from the tuner to the display controller, yes composite video.
If your car is not equipped with TV, you will need to add the TV tuner and control module equipped for TV, if you really want to receive stations, then you also need a rear window antenna (kompensor) module. That is if your rear window supports TV.
But just to get an AV input, then just add the adaptor to the tuner and poke your DVD player into that.
TV in motion is also easily done with a tool that enables it and doesn't break the navigation. This seems to work on all can gateway equipped cars although I've yet to try it on an A3.