5.1 from satelite receiver and SB X-Fi

[afoka]

Hi all,

I've got some question that i haven't found an answer on google.

I have got: TV satellite receiver with optical out (spdif Toslink), SB
X-Fi Audio PCI-E (with spdif In and out) and 5.1 speakers from Genius.

After I have connected everything: sat (OPT OUT) to sb (OTP IN) and sb
to speakers, it works great as stereo but when i turn on AC3 (when
watching channel which supports it) on my satelite reciver, I can't
hear any sound :(

Please, can anybody tell me, how should I set SB settings to capture
multichanel signal from sat receiver, encode it and sent to speakers?
Should i download some additional software that will be runing when
watching TV (I dont know maybe there is something like "active decoder
of AC3" ??).

Maybe it it not possible at all ?

I just want to hear the 5.1 sound when watching some TV chanels that
are transmited with AC3.

Please help me
Best regards Arek.

P.S. 5.1 sound works, when watching DVD or avi movies with AC3 filter