$ sudo apt-get update
$ sudo apt-get install gstreamer0.10-ffmpeg 

gstreamer0.10-ffmpeg is installed in your system.

Make ensure the gstreamer0.10-ffmpeg package were installed using the commands given below,

$ sudo dpkg-query -l | grep gstreamer0.10-ffmpeg *

You will get with gstreamer0.10-ffmpeg package name, version, architecture and description in a table

gstreamer0.10-ffmpeg package basic information: