writes As promised, version 33 of the Firefox browser will fetch the OpenH264 module from Cisco, which enables Firefox to decode and encode H.264 video, for both the <video> tag and WebRTC, which has a codec war on this matter. The module won't be a traditional NPAPI plugin, but a so-called Gecko Media Plugin (GMP), Mozilla's answer to the disliked Pepper API. Firefox had no cross-platform support for H.264 before.
Note that only the particular copy of the implementation
built and blessed by Cisco is licensed to use the h.264 patents.