morphine wrote:SNM I don't quite understand the whole situation: why do you want to decode DD on your computer at all? It seems you want to decode those iTunes tracks? Then all you have to do is have your coax out connected to the Z-5500s, and they'll take care of it.
Maybe I'm missing something here or misread, but I'm not quite understanding the scenario
I think we're getting our acronyms mixed up.
DD: Dolby Digital. Also known as AC-3, this is an audio codec for multichannel audio.
DDL: Dolby Digital Live. This is a digital encoding scheme for passing digital multichannel audio down S/PDIF connections. It takes any decoded audio from the source and transcodes it to Dolby Digital format for transport. It is up to the receiver to decode the signal.
If you want to decode audio encoded by DD/AC-3, you need a decoder like FFDShow or something built into the media player. This will take the DD compressed audio, decode it, and output PCM to your sound card for conversion into analog signals.
If you want to transcode all the audio coming out of your system to DDL for decoding by a receiver, something like the Xonar will be able to do that.