Well the only thing I could find was info on M4V files
http://www.fileinfo.com/extension/m4v
MPEG-4 file extension used for videos downloaded from the Apple iTunes store; includes TV episodes, full-length movies, and music videos; similar to an .MP4 file, but may be copy-protected using Apple's FairPlay DRM copyright protection.
To play a protected M4V file, your computer must be authorized (using iTunes) with the account that was used to purchase the video.
Unprotected M4V files may be recognized and played by other video players by changing the file extension from ".m4v" to ".mp4."
Programs that play the files
Mac OS
Apple iTunes
Apple QuickTime Player
RealNetworks RealPlayer
Miro
Windows
Apple iTunes
Apple QuickTime Player
RealNetworks RealPlayer
Media Player Classic
Miro
Linux
Miro