I just installed Ubuntu, and thus I'm unable to play movies. For example, if I run *.mkv file, I get the error of " Gstreamer backend error - Can't play the text file without video or visualization
". If I run *.avi one, it says " Gstreamer backend error -Your Gstream installation is missing a plugin
"
What should I install?
You need to install codecs.
Either you install vlc, this will intern download all codecs or install
Ubuntu restricted extras
from software center.