Moves:
1. install VirtualBox: sudo apt-get install virtualbox and configure it.
2. install gimp and inkscape inside application center.
3. transfer to the “universe source” by search the ffmpeg in application center and the using the source
4. try to play a rmvb video file and install the rm decoder according to the prompt.
The stuck problem:
Kill the dpkg process
and run: sudo dpkg –configure -a