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).