Hi there,
After asking around on the IRC it was recommended to me that I should take my problem to the alsa-devel mailing list. So here goes.
When I ran Windows (1 year+ ago) I never tried HDMI audio output, or any HDMI output for that matter. Therefore I cannot verify that HDMI audio worked in the first place. However, my GPU, and more specifically, my laptop, is specced to be able to deliver audio through HDMI. I've been looking on and off for a solution to this problem for a couple of months now, but nowhere I found a solution to the specific symptoms that I'm having.
My laptop in a nutshell:
Machine: HP Compaq 8510w Mobile Workstation Chipset: Mobile Intel PM965 with 800-MHz front side bus GPU: NVIDIA Quadro FX 570M graphics with up to 256MB dedicated memory (512 MB TurboCache) CPU: Intel Core 2 Duo Processor T9300 (2.50 GHz, 6 MB L2 cache, 800 MHz FSB)
OS: Linux x86-64 Ubuntu 11.04 Natty Narwhal nVidia Driver Version: 270.41.06
Output of alsa-info: http://paste.ubuntu.com/613101/
Output of lspci: http://paste.ubuntu.com/613123/
I really hope this is the right place for me to find a solution, with your help, and I thank you all for taking the time to read this email.
Joost Verdoorn