3GPP is a global standards for the creation, delivery and playback of multimedia over
3rd generation, wireless networks, cell phones, etc. It's based on a simplified MP4 container.
Here's a sample .3gp file and the corresponding hexadecimal dump of its header (first 256 bytes):
Marked in yellow are the patterns used by
TrID to identify a 3GPP file.
Check the MiniDumper tool to obtain an hexdump from a file in an easy way!