GStreamer isn't used on Firefox OS. We use libstagefright and vendor supplied binaries for decoding.

None of those bugs are resolved, so where was I wrong?

In fact, there's this bug for H.264 support: https://bugzilla.mozilla.org/show_bug.cgi?id=541286

It was raised in January, and it's status is: "RESOLVED WONTFIX"

The stable Firefox build, as of today(12/19/2012) does not support those codecs.

We are implementing support on desktop using OS frameworks where we can. So far we have:

- support for Linux via GStreamer landed but not built by default. It needs a bit more work.

- support for Windows 7 and above which the OP post is about

- Mac OS X is not yet underway but is planned.

- Hardware H.264 decoding on Android phones via libstagefright. Some phones supported and enabled by default. Some supported but disabled at the moment. Some unsupported.

- Hardware H.264 decoding on Firefox OS/B2G enabled by default, implemented via libstagefright. Phone vendors provide the binary blobs to do the decoding.

will you enable H.264 support only on desktops once you have working backends for Windows/Linux/OS X or will they be enabled by default as they are working? Just wondering if there will be stable releases of Firefox where some platforms have H.264 decodes and some don't.

They will be enabled by default as they are working. We already have the issue of some platforms having it and others not. Some Android devices have it with Firefox for Android and some don't for example. Linux distro's could enable the GStreamer backend and gain it while others don't as another.

For detection sites should use the API "canPlayType" and similar functionality to detect if the browser supports playback.