Firefox sound issue on build 17063 should be fixed with today's Nightly
Just thought I'd put it out there. The changes are now being merged, and should be coming with today's Nightly build. There's some discussion about backporting the change to the next stable release (58, coming in about a month) and the ESR version as well.
Posted Dec 21, 2017, 8:29 PM UTC
Just installed the latest Nightly Firefox update and Video sound is back working (version 59.0a.1(2017-12-22) (64-bit)