You can use mplayer to give you information about what codecs the file is using:
Code:
mplayer -identify -frames 0 file.3gp
A typical problem is the use of the AMR audio codec, which cannot be freely distributed. One solution is to use the debian-multimedia repository to update ffmpeg so that players based on this will handle AMR:
Code:
vi /etc/apt/sources.list
(add in the following line)
deb http://www.debian-multimedia.org stable main
apt-get update
apt-get dist-upgrade
