I have had an Acer Revo box as a media centre for a while. I recently installed Ubuntu Server (10.10) on it and polished it up with nodm (one of the most simple ways to launch an X session) and installed boxee. It's been working fine for over a month.

It's just running ALSA. I've had problems with PulseAudio/Boxee/HDMI before so I wanted to keep it simple. And that worked. It pushed both PCM and digital (AAC and various Dolby codecs) over HDMI perfectly.

But I restarted it the other day after mucking around with some nfs configuration and now there isn't any sound.

The hardware is an ION chipset. Nvidia 9400M graphics with Nvidia MCP79/7A audio.

One thing I have noticed is there doesn't appear to be any sign of a IEC958 device. A traditional fix in the past for fresh installs has been to load alsamixer, find the IEC device and toggle its mute but I can't. I'm certain this used to represent the HDMI output. It just doesn't seem to exist any more unless I run sudo alsa-utils restart while boxee is running, when I see it in an error message:

* Shutting down ALSA...  [ OK ] 
* Setting up ALSA...
* warning: 'alsactl restore' failed with error message 'alsactl: set_control:1388: Cannot write control '2:0:0:IEC958 Playback Default:0' : Operation not permitted'...
  ...done.

When nodm (and thus boxee) aren't running, I don't see this error but alsamixer still doesn't show the IEC channel.

aplay -l gives:

card 0: NVidia [HDA NVidia], device 0: ALC662 rev1 Analog [ALC662 rev1 Analog]
  Subdevices: 1/1
  Subdevice #0: subdevice #0
card 0: NVidia [HDA NVidia], device 3: HDMI 0 [HDMI 0]
  Subdevices: 0/1
  Subdevice #0: subdevice #0

Its section in lshw reads:

    *-multimedia
         description: Audio device
         product: MCP79 High Definition Audio
         vendor: nVidia Corporation
         physical id: 8
         bus info: pci@0000:00:08.0
         version: b1
         width: 32 bits
         clock: 66MHz
         capabilities: pm bus_master cap_list
         configuration: driver=HDA Intel latency=0 maxlatency=5 mingnt=2
         resources: irq:22 memory:fae78000-fae7bfff

I was running on the stock PAE kernel but now it's running on 2.6.37.1. I upgraded to see if that fixed things; it didn't.

I'm considering a reinstall but I hate doing that because a) there's a bit of custom configuration in getting X and Boxee to start on boot and b) I don't know what the problem is. If I reinstall this time, I'll end up doing that every time the sound breaks. I love Ubuntu but I don't want to install it once a month.

Is there any way to forcibly reset all alsa settings and restart from scratch (without doing a reinstall)? Any other tips?

If you need more information, just ask.