Adi Ad2000b 8-Channel High Definition Audio Codec Drivers

Without any of these solutions, you'll pretty much only be able to pass stereo PCM through the SPDIF output.

There are some players and DirectShow filters that will let you do this at the player level, like with MPC-HC and ReClock or ffdshow, but they won't encode to DD Windows sounds, only whatever they're playing. Unfortunately, I think most Gigabyte boards come with one of these, and very few of Asus'.

These will convert all 5.1 PCM audio from your system and pass it through the SPDIF output in DTS or DD form. Your audio device has to support either DTS Connect (which includes 'DTS Interactive' which is what you want), or Dolby Digital Live. Charges apply for license with premium features. ADI® AD2000B 8 -Channel High Definition Audio CODEC.

Sound & Audio: Onboard Soundcard (ADI AD2000B. iTunes doesn't fall under this criterion that I know of, so iTunes (or any other program including games) will not give you 5.1 over SPDIF you'll have to use the method below. And in the volume control panel its called High Definition Audio Device. Most video players will let you use SPDIF to pass through 5.1 DD or up to 6.1 DTS(ES) to your decoder, but your content has to have one of these formats (such as DVD content). From what you're saying it seems you don't want to use the analog connections, so SPDIF is your other option.

Adi Ad2000b 8-Channel High Definition Audio Codec Drivers