After recently upgrading to Ubuntu 18.10, Firefox isn't playing any embedded MPEG-4 video, there was no issue before the upgrade

e.g. https://twitter.com/Twitter/status/1065406263612399617

The console in dev tools reports this

The video on this page can’t be played. Your system may not have the required video codecs for: video/mp4; codecs="avc1.42E01E mp4a.40.2", video/quicktime; codecs="avc1.42E01E mp4a.40.2", video/x-m4v; codecs="avc1.42E01E mp4a.40.2" 1 1066421472464392192 HTTP “Content-Type” of “video/mp4” is not supported. Load of media resource https://video.twimg.com/tweet_video/DskVIELXgAEDAmP.mp4 failed. 1 twitter

YouTube videos play successfully, and the same link works in Chrome on the same machine. Unfortunately, I'm using 56.0.2 and, due to work restrictions, cannot upgrade to the latest release

Flashplugin-installer and ffmpeg are installed and the latest version

The "Play DRM-controlled content" option is selected

Adding ffmpeg gstreamer and flashplugin-installer has no effect

sudo apt-get install ffmpeg flashplugin-installer gstreamer1.0
Reading package lists... Done
Building dependency tree       
Reading state information... Done
gstreamer1.0-plugins-good is already the newest version (1.14.4-1ubuntu1).
gstreamer1.0-plugins-good set to manually installed.
ffmpeg is already the newest version (7:4.0.2-2).
flashplugin-installer is already the newest version (
0 upgraded, 0 newly installed, 0 to remove and 0 not upgraded.
  • 1
    Plays on my system in FF (also using 18.10). "flashplugin-installer and ffmpeg " eh what do they have to do with playing mp4s in firefox? I would add gstreamer codecs for mpeg if I was you. – Rinzwind Nov 24 '18 at 23:12
  • still not working. All seem to be the latest version, added to the original question – Joseph McCarthy Jan 2 at 16:27

I'm using 56.0.2 and, due to work restrictions, cannot upgrade to the latest release

I thought it's an ESR version, but that was 52 and 60 as it seems. I cannot find it in cosmic (1, 2) either, the current one is labeled as a security update for good reason considering the importance of browser updates (or electron apps) in this day and age.

Moving on, here are things to consider: the Cisco OpenH264 plugin will be downloaded when you first start your browser, it's not included. Your company seems to block certain software updates, check if the plugin is installed via about:addons > plugins. Regarding gstreamer I think the good plugins are not sufficient, you need to install the "bad" (contains: video/x-h264 and h264parse) ones too, if you are allowed to. May be this is helpful: https://askubuntu.com/a/636725/40581

There is also a snap for Firefox but contrary to flatpak you cannot install snaps on a per-user basis. Installing or access to snaps and flatpaks or other sources may be blocked too in this environment.

Your browser is about 8 versions behind, which is about a year (~48 weeks). I don't see how this got into 18.10/cosmic, this is seriously wrong and no wonder why some features may not work properly.

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