M4V is a video container that stores audio and video data used for iTunes files. Files of this type may be protected from illegal viewing and copying with Apple FairPlay DRM. In this case audio or video files should be bought in iTunes store. Not protected files can be viewed almost in any modern player because the format is based on MPEG-4 structure.

AVI is a multimedia container that is very popular among PC and Mac users. The format was developed by Microsoft in 1992. Usually AVI is used as a video format but unlike other formats of that time, AVI may contain both audio and video data compressed with a use of different combinations of codecs. More often such video codecs as DivX and XVID are used with .avi files. For audio playback such codecs as MP3, AC3 and PCM are used. It is possible to play AVI files with Windows Media Player or other similar programs.