Sound problem in Firefox after upgrade to 18.04
After upgrading Ubuntu to Version 18.04 Firefox 60 has no sound when playing an mp4 video.
- The same video has audio when played in Chrome.
- Youtube videos have sound in Firefox.
The speaker symbol on the video screen is x-ed out and can not be changed.
Firefox is not shown as an Application in PulseAudio when the mp4 video is played.