change mp4 `ftyp` from `isom` to `mp42`

Question

Will I be able to change the ftyp of an mp4 file?

I have two mp4 files and placed it unto media info to see what is the difference. The other mp4 plays on my SanDisk Sansa Fuze device while the other does not. The one that is playing has an ftyp of mp42. The one I encoded using megui uses isom as its codec id.

Answer 1

ffmpeg could do the job.

ffmpeg -i isom.mp4 -brand mp42 mp42.mp4

Answer 2

Try using something like WinFF to convert the files for you, it has quite a few low-level functions you may be looking for.