File Extension M4P
File extension M4P is most commonly associated with Apple iTunes audio files. M4P files are similar to both the M4A and M4B file format in that they are MPEG-4 containers capable of storing an audio stream. However, M4P files have one key difference in that they are protected by a Digital Rights Management (DRM) scheme, which prevents them being played by unauthorised users.
The vast majority of M4P files are audio tracks purchased online from Apple's iTunes music store, and are commonly encoded using AAC (Advanced Audio Coding), which is a follow-on format to MP3 offering superior sound quality at similar file sizes. M4P files incorporate Apple's FairPlay DRM copy protection, which prevents the distribution of purchased audio tracks by limiting the number of machines that the file will play on. In order to play an M4P file, the computer must be authorised via iTunes, which is done by entering the username and password of the account from which the file was downloaded. A maximum of five computers can be associated with an account at any one time, which prevents users illegally distributing content purchased from iTunes.
Files downloaded from the iTunes store are generally in M4P format, though the File extension M4A and File extension M4B extensions are also used. These are essentially the same MPEG-4 container format, albeit without DRM protection. M4A files are usually used to signify music tracks, whereas M4B files also have support for bookmarking, which allows users to record the point at which they stopped playing the file. This format is used more commonly for audio books.
M4P files can be opened on the Windows and Mac platforms using either Apple iTunes or QuickTime Player, though Apple's proprietary FairPlay DRM encryption prevents widespread support by other media playing software. Utilities make it possible to convert protected M4P files into other, more widely supported formats such as File extension MP3 or File extension WMA, though there are questions about the legality of circumventing Apple's FairPlay DRM protection system.