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I bought a Xonar DGX to hook it up to my Sony 5.1 surround system with SPDIF. Windows 10 says the SPDIF port only supports stereo and when I start the sound test it plays only sounds on FL and FR. In the settings of the SPDIF pass through device I can start the Dolby and DTS test, which plays sounds on all 6 channels. When I play AAC or DTS with VLC, only stereo will be played. When I enable "use SPDIF when possible" in VLC settings, it will play DTS in 5.1 and AAC in 2.0. Even video games like Witcher 3 or Dark Souls 3 output only 2 channels.

What do I have to do to always output 5.1 over SPDIF?

pythonimus
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1 Answers1

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If your sound card manufacturer hasn't paid for the Dolby licensing when they bought the chips then you can't really.

Pass-through from movies works because the audio has been "baked in": it has already been encoded.

For games and real-time audio, 5.1 over 2-channel needs to be matrix encoded to pass along the two wires on a coax (or fiber), and your sound card usually must do this.

It may be possible to get a matrix driver wrapper in the middle that pretends to be a 5.1 system; encodes on the fly; and then send the audio over the SPDIF on the actual soundcard, but this will cause latency and use CPU. In the past, I never even got that method to work.

Note that "Dolby Headphone for 5.1 headphone experience" is marketing speak for pretending 2-channel audio has a wide field. ( https://en.wikipedia.org/wiki/Dolby_Headphone ) It requires a compatible headphone that can decode, and the non-virtual surround sound still must be encoded (or passed through) on the sound card.

Yorik
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