You have no idea what you're doing....HDMI HD audio is not broken....been using it for 2 years through all AMD driver updates, just fine. Calm down, and do more troubleshooting. It's probably your receiver.
See, I would tend to agree...however, a month ago I had HD audio working...don't know what I did, but it was working. So then 10.12 comes out and I'm all like "OH! OPTIMIZED 6870 DRIVERS FINALLY!" so I upgraded...HD audio goes away...
OK I think, must be the new drivers, so I do a COMPLETE uninstall of all drivers (Add/Remove Programs, manual removal from Device Manager, couple runs of the newest Driver Sweeper in Safe Mode, etc.)...COMPLETELY EVERYTHING GONE! Re-install 10.10 with hotfix (same thing I was running when HD audio WAS working)...still nothing...so as far as it being my receiver with the issue I don't quite think thats the main problem as HD audio at one point was working perfectly fine.