The M4P format file is a proprietary version of advanced audio coding (AAC) for MP4 format with DRM designed and developed by Apple. They are used in music which can be downloaded from the Apple iTunes music store. M4P format files are typically audio files purchased from iTunes and protected by FairPlay digital rights management (DRM), which limits the number of computers that the file can be played on (usually, no more than five).
To play protected M4P files, you need Apple iTunes software. Furthermore, DRM protection ensures that M4P files will only play on computers authorized to play them. To authorize a computer, you have to enter correct credentials such as username and password for that account for which the audio was downloaded. The M4P format is generally used for the exchange of films and videos on the Internet. The format uses two different compressions for video and audio. Audio tracks are compressed with AAC compression and the video files with MPEG-4 video technology.
3GP is a multimedia container format defined by the 3rd Generation Partnership Project (3GPP). 3GP is a simplified version of the MP4 format and was designed to make file sizes smaller so mobile phones could support it. 3GP files can be also viewed on computer with RealPlayer or QuickTime.
To convert other video format to 3GP files that can be watched on mobile phone, you can use BlazeVideo 3GP video converter. This 3GP video converter can convert all popular video files to 3GP including HD videos.
The biggest difference between M4P and 3GP is that M4P can only played on computer but 3GP is mainly designed for mobile phones.