Firefox uses openh264 by default which sometimes stutters on videos; it can also use ffmpeg libraries to provide somewhat better experience but it's patent encumbered. Firefox Flatpak should use it only when user explicitly installed ffmpeg-full extension.

Comment on attachment 9150425 [details]
Bug 1639531 - make flatpak aware of optional ffmpeg-full extension r=mtabara

Beta/Release Uplift Approval Request

• User impact if declined: Flatpak users have poor video experience.
• Is this code covered by automated tests?: No
• Has the fix been verified in Nightly?: No
• Needs manual test from QE?: No
• If yes, steps to reproduce:
• List of other uplifts needed: None
• Risk to taking this patch: Low
• Why is the change risky/not risky? (and alternatives if risky):
• String changes made/needed:

https://hg.mozilla.org/mozilla-central/rev/e2595b61fb38

Comment on attachment 9150425 [details]
Bug 1639531 - make flatpak aware of optional ffmpeg-full extension r=mtabara

Fix video for Linux Flatpak users, the impacted population is very low but the impact for them is important, uplift approved for our last beta thanks.

https://hg.mozilla.org/releases/mozilla-beta/rev/bb2ce87358c1

Is there a way we can make it required instead of optional?

Yes; https://hg.mozilla.org/mozilla-central/file/tip/taskcluster/docker/firefox-flatpak/runme.sh#l100 should be changed to false. My understanding is that Mihai couldn't get a "clearance" for making it installed automatically due to patents, even though it's Flathub that ships the patent-encumbered extension, not Mozilla.

Note that bug 1619988 might make it unnecessary to get these to get decent performance H264 playback.

OpenH264 still has bad performance, but at least now it decodes things properly.