3GP files can be corrupted for several reasons. This page will describe some of the common reasons, and how they can be reconstructed.
Reconstruction after file deletion
Video camera files are not typically found unfinalised, but it could happen if there was a camera failure, or maybe the memory chip or battery was removed before completion. The most likely indication of this would be 'mdat' segement length is zero. This means that it is very likely that the 'moov' segment has not been written.
The solution to the above is to create a new moov segment. As the possible variations are very large, the approach does require a sample valid file, from which the moov parameters can be analysed and used. CnW software will automatically scan the media for a suitable file and use it. The approach does require the locations of each frame to be found by parsing the mdat segment. Frames are indicated in several ways depending on which codec has been used to record the video. The codec will be determined from the sample moov segemnt is the sample file.