I'm running Windows 7 on a computer with an Audigy Platinum eX sound card connected to a surround receiver via optical cabling.
Sound works fine when listening to non-surround audio sources, such as windows sounds or MP3. However, when I view a DVD in Media Center and the SPDIF passthrough kicks in, I can only hear an awful noise instead of the movie soundtrack.
Also, the receiver does not show the Dolby Digital or DTS symbol, but stays at Dolby Prologic, so it seems it doesn't identify the sound encoding properly.
I could switch off SPDIF passthrough and use the sound card's decoder instead, but that's not an option for me since it would create more problems with regular MP3 playback via additional Stereo Receiver which is also connected to the same sound card.
I've tried both the default Audigy drivers that come with Windows 7 and the latest drivers from the Soundblaster website, but the problem remains unchanged. Also, I have ensured that the receiver's Dolby Digital decoder is not broken by successfully connecting it to my PS3 to view a Dolby Digital DVD. Besides, SPDIF passthrough was working fine in Vista before I upgraded to Windows 7.
Is there anything else I could try?