User Agent: Mozilla/5.0 (X11; Linux x86_64; rv:81.0) Gecko/20100101 Firefox/81.0

Steps to reproduce:

The Firefox 81.0 Flatpak plays videos on certain websites in a manner that looks like up to half the number of frames per second is being dropped. I've experienced this issue when playing videos from every public instance of Invidious (https://github.com/iv-org/invidious/wiki/Invidious-Instances) and every public instance of Nitter (https://github.com/zedeus/nitter/wiki/Instances).

I've attached a copy of my system's Flatpak Firefox troubleshooting report to this bug report. My system is running Debian 10.5 and Flatpak 1.8.2-1~bpo10+1.

Actual results:

Videos from every public instance of Invidious and every public instance of Nitter play back in a manner that looks like up to half the number of frames per second is being dropped. Audio is unaffected and plays back normally.

However, videos from YouTube are not affected by this issue.

Expected results:

Videos from all websites should play back normally, with no dropped frames. The Snap versions of Firefox that I previously used (80.0.1 and earlier) on the same system did not exhibit this issue.

Hi,

I wasn't able to reproduce the bug but I've chosen a component for this bug in hope that someone with more expertise may look at it. We'll await for their answer. If you consider that there's another component that's more proper for this case you may change it. I think this would be a priority S2.

Regards, Flor.

Hi, as you said, this issue is a recent regression, would you mind to use mozregression to find the culprit?

In addition, I've tried to play a video from one of those public instances, the video format is H.264/AVC, which would be decoded by OpenH264. If the problem is inside the package of openH264 used by flatpack, then we can almost do nothing to help. In addition, we have a similar problem which is also related with video decoding issue on flatpak (1633341).

Currently all flatpak related issues would be marked as P5.

Thank you.

[1] https://mozilla.github.io/mozregression/
[2] https://yewtu.be/watch?v=HwOmqeZua0k

I think I've found the root cause of this issue. The org.freedesktop.Platform.ffmpeg-full//19.08 extension was not installed on my system. Manually installing the extension fixed the issue. The Firefox Flatpak on my system now plays H.264 videos smoothly, with no apparent missing frames. It seems that the org.freedesktop.Platform.openh264 extension that was installed alongside org.mozilla.firefox has some major bugs that have not been ironed out yet. (I'm assuming that Firefox was using the openh264 extension before I installed ffmpeg-full.)

Looking at the metadata for org.mozilla.firefox, I noticed that the [Extension org.freedesktop.Platform.ffmpeg-full] section has no-autodownload set to true. This explains why the extension was not installed on my system when I first installed org.mozilla.firefox.

I think that no-autodownload should be set to false in future Firefox Flatpak releases. It's unreasonable to expect Firefox Flatpak users to be aware of the need to manually install the ffmpeg-full extension for Firefox to play H.264 videos smoothly. Users expect video playback on a modern web browser to work well out of the box, and I think that's reasonable. After all, video playback is today a core browser feature. Also, all relevant Firefox and Flatpak documentation currently does not mention anything about this need to install the extension. I was made aware of such a need only after stumbling upon TIZ's topic on the Flathub forum regarding this same issue.

That is an interesting topic. On other platforms, we have platform native decoders which can be used to decode h264. However, on Linux, we don't have that. According to our policy (), we can't encourage users to download or use ffmpeg, but if it's already installed in users' computers, then we would use ffmpeg to decode h264 which is the only way to play h264 on linux.

As this issue is fixed after reporter installed ffmpeg, I'm going to close this bug.