Solve Firefox problems

No audio with youtube videos under centos

firefox web browser plays video output without sound
Centos plays video sound ok with other applications, eg VLC.
No error messages.

Solution

Problem has nothing to do with firefox! Fiddling with firefox settings does not help.

Goto Centos Settings | sound | applications
Ensure sound volume slider for firefox is not 0 (i.e. drag it to right)

This causes check box to change to "on" and firefox can now play audio track on videos ok. (No need to restart firefox.)

W.B.Langdon 8 Nov 2021