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Created August 9, 2026 00:13
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Fixing Firefox H.264/AAC playback issues after the FFmpeg upgrade on Arch Linux using ffmpeg4.4
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firefox-ffmpeg9-arch-video-playback.md

Firefox video playback broken after FFmpeg 9 on Arch Linux

Date: 2026-08-09
Affected setup: Arch/EndeavourOS, Firefox/Firefox Developer Edition, FFmpeg 9

Symptoms

After Arch upgraded FFmpeg from 8.x to 9.0, Firefox could no longer play some H.264/AAC video streams. Twitch, for example, could fail with:

This video is either unavailable or not supported in this browser. (Error #4000)

In about:support → Codec Support Information, H.264 and AAC software decoding showed as unsupported:

H264  Software Decoding: Unsupported
AAC   Software Decoding: Unsupported

Installing Arch's compatibility package fixed it:

sudo pacman -S ffmpeg4.4

After restarting Firefox:

H264  Software Decoding: Supported
AAC   Software Decoding: Supported
HEVC  Software Decoding: Supported

Video playback then worked again.

What happened?

Arch moved to FFmpeg 9.0 on 2026-08-04. This was an ABI transition: for example, libavcodec.so.62 became libavcodec.so.63, along with similar SONAME bumps for the other FFmpeg libraries.

Some Firefox-family builds were temporarily incompatible with the new FFmpeg libraries. A nearly identical report appeared on the Arch forum immediately after the FFmpeg 9 update: LibreWolf lost H.264/AAC playback, ffmpeg4.4 restored it, and a later LibreWolf rebuild fixed the problem without the compatibility package.

This is not unprecedented. Mozilla tracked essentially the same failure during the FFmpeg 7 → 8 transition in 2025; installing ffmpeg4.4 also restored playback there.

Why does ffmpeg4.4 exist?

ffmpeg4.4 is an official Arch compatibility package. It dates back to the FFmpeg 5.0 transition in January 2022, when FFmpeg removed old APIs and some applications were not yet compatible. Arch explicitly recommended ffmpeg4.4 as a fallback while upstream projects caught up.

It can coexist with the current FFmpeg package because it provides older versioned shared libraries such as:

/usr/lib/libavcodec.so.58
/usr/lib/libavformat.so.58

while current FFmpeg 9 provides newer ABI versions.

Arch intended to progressively phase ffmpeg4.4 out, but the removal task created in February 2022 is still incomplete. The package remains useful for compatibility problems like this one.

Fix

For an affected Arch/EndeavourOS system:

sudo pacman -S ffmpeg4.4

Completely restart Firefox and check:

about:support → Codec Support Information

H.264 and AAC should show Supported.

This should be treated as a compatibility workaround. Once the affected browser package is rebuilt/fixed for the current FFmpeg ABI, ffmpeg4.4 may no longer be necessary.

Sources

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