I'm trying to get 5.1 surround sound to work using:
iec958:CARD=SB,DEV=0 HDA ATI SB, ALC887-VD Digital IEC958 (S/PDIF) Digital Audio Output
and it almost works. Using alsa's speaker-test utility I get front and center channels but both surround speaker channels play through the front speakers rather than the surround speakers. No LFE.
( I ran
speaker-test -diec958:CARD=SB,DEV=0 -c6)
Using mythtv's speaker test I get I similar results but, interestingly, the LFE works as well from mythtv.
I suspect that, for whatever reason, Ubuntu is not seeing/configuring the device correctly because in the Settings, Sound tab I only have a choice for IEC958 Digital Stereo -- no surround sound options are present, and the "Test Speakers" function from in there only shows the two stereo speakers, of course. The sound device is a RealTek ALC887-VD on an ASUS M5A78L-M mobo.
Any ideas of things to try? I've poked around online for many hours now to no avail.