I've been trying to find the answer to this for a while and turned up nothing. I've rented a couple of movies from the Play store that were listed as supporting 5.1 audio but they all played back in stereo. This is in Chrome v51.0.2704 on a Windows 10 PC with fully functioning multi-channel audio via HDMI to my receiver. Games, native apps etc. all output in 5.1.
I've seen a few suggestions to try disabling the Flash plugin but this wasn't successful. If Chrome/Chromium does indeed support 5.1, any ideas how to begin troubleshooting the issue?
Many thanks.