I am trying to record audio using the media recorder class, in 3gp
format and then later split this recorded file into 2 or more pieces.

I have a way to extract the AMR core and parse it and split it into
the desired AMR files.
But I am not sure how to wrap it into a 3gp container. Can somebody
please share information on this.

Right now when i record audio in android there seems to be more than
one box of data. the ftype box, and then a few more mdat boxes
etc...where can i find info on how android wraps AMR data into 3gp..
does it add any padding data?