Thank you for your reply, AndyClift. I'm converting mostly from AVI to MP4 - the files are all converting perfectly fine, and everything plays via Apple TV, my issue is with the video files I have that are not in the widescreen format. I have several that I converted and it's only now that I've played them through Apple TV that I've realised they don't play full screen. I'm looking for a solution to make all my files the same aspect ratio - I don't mind if they're widescreen (although preferably I'd like them to play full screen) but the ones that play with the huge black gaps at either side of the picture are bothering me. Any suggestions much appreciated.