I've noticed there is ALSA, OSS, and PULSEAUDIO. How do I know what I'm using?
(I'm running MythBuntu 10.04 and I want to figure out how to make all apps - VLC, Basero etc output via the SPDIF).
Different applications can make use of different "sound systems". For some applications, you can choose the sound backend at run time (e.g., via a preference setting); for other, this has to be a compile-time choice (therefore, it's up to the package maintainer to select one).
Still, some applications do not support PulseAudio and only offer a choice of ALSA/OSS: older versions of Skype and Adobe Flash are the primary example, but also the free music player Aqualung.
So, in the end, the answer is: it's application-specific, and you might need to dig into the application preferences or upgrade/recompile to get them working the way you want.
If your sound is working, right click on the Volume icon in the taskbar, and click preferences. The System you are using will be mentioned at the top.
PS: Thats how it happens in Ubuntu 9.04, which I am using now.
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