3GP (or Third Generation Partnership Project) is one of the most common video formats capable of playback on standard mobile devices. These are typically low-to-mid grade phones, while SmartPhones tend to be capable of playing higher quality and higher frame rate MP4 and other video formats.
It is important for any video message designed for widespread distribution to also be converted into this format, as for the foreseeable future, it will be the dominant choice of video playback formats for Mobile Phones worldwide (though MP4 is slowly gaining dominance and adoption).
- wikipedia: 3GP
- 3GPConverter Project: http://sourceforge.net/project/showfiles.php?group_id=192375
- AMR Audio Codec for 3GP video and Mobile audio files: http://www.penguin.cz/~utx/amr
- Ubuntu Forums section on how to compile ffmpeg with AMR support to ensure 3GP conversion/streaming capabilities: http://ubuntuforums.org/showthread.php?p=2960258