I'm using an SB Audigy NX for my sound card. I've been playing around with alsamixer trying to get the digital (optical) output to work. I got it to work once, but then rebooted without storing the alsa settings and I can't get it to work anymore.

When I look at the external box itself, I can see a red light in the digital out light up if digital out is working. Right now, I can't even get that output to light up in red, so I know that the soundcard is not outputting properly. Analog sound works. I have all of the volumes across the board turned to max in alsamixer.

1. If you set up digital out properly, will all sound come out of it, or only if you are watching something encoded with 5.1 digital sound. (i.e. an XVID or something, not broadcast tv.)

2. What are the proper digital settings in alsamixer? Should I be using ECM? SPDIF?

3. Are there any other files that come into play? Should I be looking somewhere else.

I got it to work briefly while watching an XVID not recorded by Myth, so I guess it was using XINE. I don't know if XINE has different sound settings than the regular app that displays myth video. If anyone has any suggestions, I'd greatly appreciate them.

_________________
Currently running: R5.5, HD5000 x 2, PVR150, Athlon 64 3000+, Chaintech VNF4, 1GB RAM, 2 x 250GB in LVM, MSI NX6200TC -> AA 9A60 -> HDTV

Have a look at the following guides, they should help.

http://knoppmythwiki.org/index.php?page=DigitalAudioHowTo
http://www.mythtv.info/moin.cgi/DigitalSoundHowTo