[wjoe]

They work for me, Firefox 32.0.3 on Arch Linux. You'll likely need some gstreamer packages installed (I think the package on Arch is gst-plugins-good for h264), same as for watching YouTube videos in HTML5 mode rather than Flash.

There's also an about:config option "media.gstreamer.enabled" which needs to be set to true, but I don't remember ever having to set this myself.

[ssalenik]

I'm also on Arch. I had to install the 'gst-libav' package (possibly in adition to the gst-plugins-good?) for it to work. Thanks.