digital audio (spdif) passthrough?

[victorclaessen]

Hi,

I was wondering if it was possible to have a Windows guest on a Linux host use the physical mainboard's SPDIF output? I would like to feed DTS audio to an external decoder from a Windows guest.

Best regards,

V.

[mpack]

The guest can't use host hardware directly, the guest only uses virtual hardware.

The guest uses the host to output audio. If you can enable the SPDIF output on the host, then the guests output will also appear there.

[victorclaessen]

Thanks for the reply.

I understand that the guest OS is dealing with a virtual device. It's just that I did not notice a digital playback option on the virtual Intel HD Audio device in the guest machine.

In a host machine I see this, for instance, if I go to the Playback Devices screen.:

Windows 7 - Sound devices panel on a physical machine

screen1.png (48.25 KiB) Viewed 2152 times

Digital output properties panel

screen2.png (43.59 KiB) Viewed 2152 times

Supported Formats Tab

screen3.png (42.47 KiB) Viewed 2152 times

Where I can select that my Amplifier knows what to do with Digital Audio (DTS format in this case).

In the guest machine I see only 'Speakers' in the Playback Devices list. It doesn't seem plausible that the guest Windows will send digital audio to a virtual soundcard that it thinks is analog-only, right?

I realise I may end up having to test this myself; I was just hoping someone had tried this before.
I suppose it would be possible to attach a USB-soundcard with SPDIF-output and assign that to the VM, but I'd rather use the host's onboard output.

[michaln]

I'm not sure how you imagine a VM would process analog signals. All the audio data a VM inputs and outputs have to be digital at the point of entering/leaving the VM.

[victorclaessen]

Valid point. A test is in order. I will aim to report back later this week when the host machine arrives and the guest is set up.