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Old 04-18-08, 12:09 PM   #8
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Join Date: Apr 2008
Posts: 2
Default Re: X-fi to 5.1 Receiver?

My friend has the same problem trying to get the Creative DDTS100 receiver to work with non AC3/DTS audio sources on the PC.

Basically to sum it up, the ONLY way you will get 5.1 sound out of a receiver is when the input format to the receiver is Dolby Digital or DTS (Some receivers supports AAC as well, for HDDVD/BluRay).

The main reason for this is that the SPDIF (Coaxial,Optical) specification only provides bandwidth for 2 uncompressed channels of audio. If you want more than 2 channels, they have to be compressed using Dolby Digital/DTS/AAC.

When you watch movies on the PC (with filters configured to passthrough AC3/DTS) you will get 5.1, because the precompressed audio stream from the movie is directly piped to the receiver.

Whereas when you play games, the PC outputs multichannel uncompressed PCM audio. The only way to fit so much data into a single SPDIF connection is to compress it in realtime using Dolby Digital Live/DTS Interactive.

Personally, I think the X-Fi Prelude drivers can be hacked to work on the other X-Fi cards and provide all the extra features such as Dolby Digital Live encoding etc. Since the X-Fi processor is fully programmable, its only a matter of making the drivers to utilize it to perform Dolby Digital Live encoding.

Cards like the X-Fi Prelude supports hardware encoding of global PC output into Dolby Digital, or DTS.

There are software workarounds though, but they will use the CPU and reduce performance.
I think AC3Filter can encode global PCM output into AC3 and pipe it out using SPDIF Passthrough. You receiver will be able to decode this into 5.1.
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