Firefox Can Only Play a Still Frame of Video

[ElliotKillick]

Firefox only seems to be able to play a single frame of video. I've already diagnosed why this is happening with both GStreamer and FFmpeg test commands leading to the same root issue.

Firefox doesn't seem to like the YUV video format but when I tried an MJPEG stream (stream of JPEG images, which is a common format for webcams) it works fine and plays the video back seamlessly.

We could add a conversion to the MJPEG format but I tested that and it results in big latency increase (not to mention the added attack surface). Additionally, to do that GStreamer actually relies on a libav (fork of FFmpeg) conversion algorithm that got bindings added to it for GStreamer. This is the element in question: https://gstreamer.freedesktop.org/documentation/libav/avenc_mjpeg.html. This means it's not packaged in Fedora due to the patent issues with FFmpeg.

So, with the problem diagnosed I'm going to try and make quick work on finding where the bug is so it can be patched. Firefox is the only application I've tested that has had problems so it may be a Firefox bug with YUV formats. I looked it up and Firefox should have full support for YUV webcam video just like Chromium but that doesn't appear to be the case.

Going to try and fix this ASAP because I hate to leave Firefox at a disadvantage.