Thats what video compositing is for I am not a QTKit expert but just quick glance over the documentation they offer QTMovieLayer which allows you to have multip

Thats what video compositing is for I am not a QTKit expert but just quick glance over the documentation they offer QTMovieLayer which allows you to have multiple layers of media which will be composited later ( i.e. one for video, one for the media controls, etc )