Apple uses M4V to encode video files in its iTunes Store. The primary difference is that M4V files may optionally be protected by DRM copy protection. The M4V file format is a video container format developed by Apple and is very similar to the MP4 format. It is intended to serve as a universal format for storing common multimedia content, like movies or TV shows.
The Matroska Multimedia Container is an open standard free container format, a file format that can hold an unlimited number of video, audio, picture, or subtitle tracks in one file.
