I have Ubuntu 18.04.3 LTS installed on by Dell with firefox 68.0.2 (64-bit). ubuntu-restricted-extras is installed and several option in the about:config are enabled for mp4. A few days ago MP4 did work on firefox. After some updated from Ubuntu, it stopped working. I reinstalled ubuntu-restricted-extras abd firefox (options about:config enabled after reinstall).

Also note the VLC is installed and can play MP4 files.

https://html5test.com/ report for video codecs:

  • MP4 with H.264 support: No
  • MP4 with H.265 support: No
  • TS with H.264 support: No
  • TS with H.265 support: No
  • WebM with VP8 support: Yes
  • WebM with VP9 support: Yes

Does anyone know how to fix this, or know how to let firefox log why it can't play mp4 (and where to find those logs).

  • 1
    Check how to install H.264 for possible solution. – Michal Przybylowicz Sep 3 '19 at 9:58
  • Followed all those steps but firefox is still unable to play mp4. Also VLC can play an mp4 (H264 MPEG-4) video. So I think is something with firefox (but correct if I'm wrong). – David Sep 3 '19 at 16:23
  • It would be interesting to see how Chromium on your system performed with the same test? If Chromium is ok I suspect that you need to install the stock FFmpeg from the Ubuntu repositories... – andrew.46 Sep 4 '19 at 1:37
  • Chromium can play MP4 with H.264. However, when I run apt install ffmpeg (as sudo), it report that it has the newest version installed. Am I installing the correct package, or has the stock ffmpeg another name? – David Sep 4 '19 at 9:16

After a while resting it, I decided to try again. First post says again to install ffmpeg package. Instead of trying installing it by apt, I tried ffmpeg -version. This showed me an error that libva.so.1 was not found. libva.so.2 was available. Making a symbolic link named libva.so.1 (to libva.so) and doing this for couple other libraries worked for me.


This was the issue that came up when I was looking for solutions to why firefox was not playing mp4s.

@michals comment on the question above led me to the solution I needed: https://askubuntu.com/a/1072894/363742

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