If you installed Fedora 16 and added the RPM fusion repositories and you still can’t watch .mkv videos because of a missing H.264 decoder plugin.
Here is how to fix it.
You are still missing a required package. Add the following package…and you should be good to go.
sudo yum install gstreamer-ffmpeg
However, If you need full instructions for enabling the RPM fusion repositories here they are also. The first two lines add the necessary repositories. The last line installs the necessary plugins for variety of video formats as well as viewing DVDs.
sudo yum localinstall --nogpgcheck http://download1.rpmfusion.org/free/fedora/rpmfusion-free-release-stable.noarch.rpm sudo yum localinstall --nogpgcheck http://download1.rpmfusion.org/nonfree/fedora/rpmfusion-nonfree-release-stable.noarch.rpm sudo yum install gstreamer gstreamer-plugins-good gstreamer-plugins-bad gstreamer-plugins-ugly gstreamer-ffmpeg libdvdread libdvdnav lsdvd
Alternatively, you can also install and use vlc or smplayer to view mkv videos–both can decode H.254 .