With MPMoviePlayerControllers's, scaling a movie is easy with setting MPMovieScalingMode. (like MPMovieScalingModeFill, MPMovieScalingModeAspectFill)
With AVPlayer/AVPlayerLayer I can't seem to find anything like that. Do I have to do this myself? If so, how do I start on this?
Take a look at videoGravity
property in AVPlayerLayer, looks like it is what you need.