Arch Linux - Firefox H.264 Playback
Jul 16, 2015
When you first install Firefox on Arch it does not come with the packages necessary to playback H.264 video on YouTube (HTML5).
First off I recommend installing every possible gstreamer plugin.
sudo pacman -Ss gstreamer0.10
Next install the optional Firefox packages.
sudo pacman -S gst-libav gst-plugins-good
Restart Firefox and H.264 HTML5 playback should work.