I've found another program that is like a front end for ffmpeg.
http://www.kde-apps.org/content/show.ph ... tent=50959
It actually installs service menus so If you right click on the movie file then you can convert it to what ever you like.
If you install it then you need to modify the ./install.sh script else it won't install. It needs to read like this:
cp src/kvm*.desktop /usr/kde/3.5/share/apps/konqueror/servicemenus/
cp src/kvm /usr/kde/3.5/bin/
chmod a+rx /usr/kde/3.5/bin/kvm
chmod a+r /usr/kde/3.5/share/apps/konqueror/servicemenus/kvm*.desktop
echo "Installation completed. Good bye."
All the best
p.s. This might be useful for figuring out how to use ffmpeg http://ffmpeg.mplayerhq.hu/ffmpeg-doc.html