Recently, my computer stopped being able to play mp4, 3pg, avi, mkv, and more media. VLC will get it to work, nothing else does, and when I try to play it with the normal player it always tries to find codecs to install, when just yesterday everything worked fine
SnapOverflow
Make sure you have the ubuntu-restricted-extras package installed, as well as the gstreamer0.10-plugins-ugly-multiverse and gstreamer0.10-plugins-bad-multiverse packages. You can find them in Software Center; if they don't show up there go to edit->Software Sources and make sure you have Multiverse enabled.