The only option is to install a video-in capable system such as the Audi factory TV module (or some after-market solution). Then you could just plug the iPod Movie composite video out to the Audi TV module video-in:
Notes on retrofitting TV module Audi A6/Q7/A8 (should be same for A5)
http://www.geocities.com/a6retrofit/articles/a6tvmodule.html
Audi Music Interface won't help you, it is for audio only.
For the TV module to work the car has to have the full MMI (i.e. has to have navi):
Difference between standard radio Concert/Symphony and the optional DVD navigation's MMI controls in B8 platform Audi A4 and A5
http://www.geocities.com/a6retrofit/articles/a4a5realmmi.html