Apologies if this is the wrong place to put this but I've recently built a custom gaming HTPC and everything's working well apart from I can't get 5.1 over HDMI from my AMD 7770. If I right-click the volume icon and attempt to configure the listed device it only ever gives me the option of 2 channel stereo.
In terms of setup, the 7770 goes into a Sony STR DH800 receiver via hdmi and i'm running the 64-bit Win8 preview. I'm fairly certain the issue isn't with the receiver as I used it with a laptop previously to get 5.1 via hdmi with no issues.
I'm wondering if it may be a driver issue. I've tried Catalyst 12.6 + 12.7 beta to no avail but have noticed that rather than being listed as an AMD High Definition HDMI device, it appears as a generic High Definition HDMI device, i.e. no mention of AMD and when probing further the drivers seem to be Microsoft, suggesting that maybe the AMD audio component of the catalyst suite isn't installing. Perhaps this relates to the issue?
This used to be a separate download, but it looks like it's now part of the Catalyst package, so I would suggest reinstalling the drivers, maybe doing a custom install so you can make sure the HDMI audio driver is checked to be installed.
Well I finally managed to resolve the issue (sort of), so will post the solution that worked for me in case any others come across similar issues:
It appears, for whatever reason, the latest version(s) of catalyst drivers will not install the necessary HDMI audio driver for the 7770 graphics card. Whether or not this relates to my particular model of card and/or OS version (Windows 8 64-bit Release Preview), I don't know.
In order to get the device working correctly (and obtain full 5.1 channel audio as a result) was to obtain the Hardware ID which can be done by the following:
Start -> Control Panel -> Device Manager -> Sound, video and game controllers -> *audio device* -right-click, Properties -> Details Tab -> Select 'Hardware Ids' from the 'Property' drop-down menu -> right-click 'Value' and select copy
Paste this into Google to (hopefully) bring up drivers that specifically mention compatibility with the designated audio device, install and hope for the best.
As it happens, it was version 11.4 Catalyst drivers that did the trick for me. I was able to do a custom install and select just the AMD HDMI Audio Device driver, which, upon restarting was fully functional.