I want to decode dolby audio ( from my HDTV ) coming in to my HTPC via the line-in
jack. I have alsa controls my soundblaster audigy card.

With my current setup, I can use VLC to play a mythtv recorded HDTV show. I can
tell VLC to use 5.1 surround sound and it will decode the dolby audio into 5.1
surround sound that my Logitech X-530 ( non-digital ) speakers will play.

I want to start playing my HDTV Audio via my HTPC speakers... as-is.. using line-in
just gives me stereo output on all 5.1 speakers.... I don't get the 5.1 surround
sound processing on it. Is there a way to enable the dolby digital decoding on the
line-in jack?

more details:
Fedora FC6
Soundblaster Audigy ( analog ) sound card
mythtv backend ( air2pc for atsc hdtv recording )
VLC ( used most of the time for displaying the HDTV recoded shows and DVD .iso files
off of my NAS server )
HDTV ( LG, Plasma, L/R audio out fed into my line-in jack on my SB card. )

Thanks - jack