From Just Solve the File Format Problem
3GP, but with some extensions and limitations that differ from that format.3G2 (or "3GPP2 file format") is a video or audio container format from the Third Generation Partnership Project (3GPP), intended for use on mobile devices. It is related to
It is based on MPEG-4 Part 12.
3G2 files can be identified by the presence of a 3G2 brand in the "ftyp" box (see boxes/atoms format for information about brands). The following brands are known: