I'm running Ubuntu 12.10 and having trouble with the audio output through HDMI on my Acer Aspire one 722. It's using an AMD c-60. I was able to add in the
radeon.audio=1 kernel parameter, which was supposed to enable HDMI audio playback but even after running
update-grub and rebooting, the problem persists when I choose HDMI as the audio output after plugging in my HDMI cable.
At this point, I'm not sure what else to do.