Specifying specific ALSA device to use for sound output / ALSA loopback / JACK

[datenwolf]

Hi,

I'm currently struggling with the "new" (I guess it's been a few years,
but so far I've never needed them) way to specify audio device emulation.

The TL;DR of the task at hand I want to solve is: I want to make qemu
use a snd-aloop device (let this be card 3) in a duplex configuration.
In my case that would be card 3, device 0, subdevice 0, so in ALSA terms
hw:3,0,0 – however this uses commas, which are already a separator for
the suboptions of the -audiodev options.

Even after reading the documentation for the 7th time or so, I still
struggle to understand how some of the parameters fit together. When
using the following command line

qemu-system-x86_64 \
        -enable-kvm \
        -smp 2 \
        -m 2G \
        -usbdevice tablet \
        -audiodev alsa,id=alsa,in.dev=hw:3,out.dev=hw:3 \
        -soundhw hda \
        ...

I'm told on stderr that

> audio: Device hda: audiodev default parameter is deprecated,
> please specify audiodev=alsa

If I then try `-audiodev=alsa` this is taken as an invalid option.

The slightly longer version of my problem statement is, that I'd like to
connect qemu to a running JACK audio instance.

Unfortunately when used with qemu that ALSA plugin fails to connect to
the JACK server, using the following command line

qemu-system-x86_64 \
        -enable-kvm \
        -smp 2 \
        -m 2G \
        -usbdevice tablet \
        -audiodev alsa,id=alsa,in.dev=jack,out.dev=jack \
        -soundhw hda \
        ...

it fails with the following diagnostic output.

> cannot connect system:capture_1 to alsa-jack.jackC.24006.70:in_000
> alsa: Could not initialize ADC
> alsa: Failed to apply audio parameters
> alsa: Reason: Input/output error
> alsa: Could not initialize ADC
> alsa: Failed to set format 2
> alsa: Reason: Invalid argument

So this is somewhat a XY question: I want to connect it to JACK and
think that I might be able to make this work though snd-aloop, but so
far without success.

And pointers?


Cheers,
dw