Missing H.264 codecs for Flatpak on Firefox and VLC on Kinoite/Silverblue

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1

I can’t get H.264 video to play in Firefox or VLC from the Flatpaks on neither Kinoite nor Silverblue.

Firefox flatpak tosses:

Couldn’t open avcodec

VLC flatpak (3.0.21 Vetinari) barks:

Codec not supported:
VLC could not decode the format "h264" (H264 - MPEG-4 AVC (part 10))

By contrast, if I do a “dnf install vlc” in a toolbox and run vlc, it plays the video fine. LosslessCut from flatpak also imports and plays the video just fine.

“Discover–Software Center” claims that I have installed the “Codecs Extra Extension”, the “FFmpeg extension with extra codecs” and “org.freedesktop.Paltform.codecs_extra.i386”.

Any suggestions for how to get the Flatpaks to install/recognize the codec?

Thanks.

Edit: This is Fedora 42-based so …

% uname -a
Linux fedora 6.17.7-200.fc42.x86_64 #1 SMP PREEMPT_DYNAMIC Sun Nov  2 17:43:34 UTC 2025 x86_64 GNU/Linux
3

Most Flatpaks have a dep on org.freedesktop.Platform.ffmpeg-full. Can you check if that’s installed?

4

You can either go with Flatpaks from Flathub, which brings the appropriate runtime extensions, or, if you’d want to use Flatpaks from Fedora, then you’d have to layer packages from RPMFusion:

rpm-ostree install libavcodec-freeworld

(See also how to add the RPMFusion repos to atomic desktop, if not already done, by following the corresponding instructions.)

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5

org.freedesktop.Platform.ffmpeg-full.

That does not appear to be installed and I don’t even see anything like it listed from search.

6

VLC is showing as installed from Flathub and still does not have the codec.

7

perhaps you could try my script which installs all extra coders (except experimental vulcan) that should be sufficient for most videos:

it was originally designed for another issue, but it installs all the codecs that are usually missing.

9

This appears to be a bug in “Discover” managing the software. It claimed that things were installed from Flathub, but flatpak list showed otherwise.

Once I used the command line to force everything to be actually installed from Flathub, the codecs are fine.

Thanks for all the help.

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