Comment 3 for bug 691135

I have HDMI audio (surround 5.1) working with a GT430 on Ubuntu 11.04 beta2. After reading various pages online, I found nothing conclusive, but eventually it worked.

Edit /etc/modprobe.d/alsa-base.conf

Add the line:-

options snd-hda-intel probe_mask=8

I also cleared the users pulseaudio configuration, but I don't know if that was required:

rm -R ~/.pulse

Then reboot.

FYI, this is how I came to the answer:-

It became apparent that there are four hdmi devices, of which only one is the real device. Whether this is in the hardware or just due to the hdmi audio driver, I have know idea.

1. Disabled onboard audio (to simplify things and make the HDMI device CARD 0).
2. Use "aplay -l" to list the audio devices. My system showed four (0 through to 3).
3. Use "speaker-test --channels 6 --test=wav --device hdmi:0,X" (where the X on the end is the hdmi device to use)

For example, on my system the following command played the audio when running the speaker test:-
speaker-test --channels 6 --test=wav --device hdmi:0,3

4. Adding the probe_mask value to alsa-base.conf I noticed the available hdmi devices was reduced.
5. After noticing the field was a mask, I used the value 8 to specify only the fourth device (device 3).