[Alsa-user] SPDIF/HDMI Pass Through: Only 2 channels?

[<bra...@br...>]

Hi All,

I've installed ALSA 1.0.19 on a fresh install of Mythbuntu 8.10 on two
seperate machines, and I am trying to get digital audio pass through to
work properly. One machine with an ALC888 soundcard with SPDIF output, and
the other with a VT1708B soundcard with HDMI output. I have digital output
working using the mplayer "-ao alsa:device=spdif" or "-ao alsa:device=hdmi"
commands respectively, and the Dolby Digital and DTS indicators light up on
my receiver that it is getting a valid digital audio stream. Ultimately I
know it works as I can hear the audio tracks in my movies.

The problem I am having is that I only seem to be getting 2 channels on
both machines, and not only in mplayer as I've tested using speaker-test
and also MythDVD. Both these cards are capable of 7.1 sound, but ultimately
I need to configure them to output 5.1 (as that is all the receivers they
are being connected to are capable of). I've scoured the Internet, but
don't seem to be able to find any information on configuring the number of
channels for SPDIF output. Can someone please help me?