Firefox audio issue with 6 channel selection


Jun 12, 2016

I have an audio problem with Firefox. Version is 60.0.1 , 64bit. Setup Win 7x64, xonar dgx sound card. This is a recent issue, from 60.0 I think.

On some youtube/twitter videos I only get sound in the left speaker if I select the 6 channel option. The selected output is headphones, but the card allows me to select from 2 to 8 input channels (which I use for 5.1/7.1 sources with dolby headphone (virtualization).
If I select the 2 channel option then it works fine. I have tried it both with IE 11 and Opera and the sound is fine when 6 channel is selected.
I have tried disabling all the addons, same issue.

Below are 2 links of videos in which the problem manifests itself (the subject of the videos is not relevant, they are just an example):

2 links of videos that work fine with 6 channel enabled: