I have a Gigabyte UD5H motherboard (Intel Z77 chipset) with onboard HDMI and an Intel i5 3750K CPU. I'm running Ubuntu 12.10 64 bit. I do not have a dedicated graphics card.
I have connected the PC to the TV over HDMI. The graphics seems to work fine (presumably the HD4000 integrated graphics are doing their thing correctly).
The problem I'm having is that on first boot, audio works OK over HDMI. If I turn the TV off but leave the PC on, audio no longer is available over HDMI. The graphics continue to work though.
If I go to Sound Settings, HDMI doesn't even show up as an available audio output (like it would on first boot).
I've tried killing and restarting pulseaudio but that doesn't work. Rebooting solves the issue but since the PC is a HTPC I can't keep rebooting it every time the TV is turned off!
Is there a way to fix this? Do I need any special drivers?