Capture desktop audio

[Fractal-Tess]

Hey there,

Is there a way to capture desktop audio on Linux using wavy?
I've been searching for some time, and I've looked through cpal, sfml and rodio, but as far as I can see, they do not seem to support this functionality.

[AldaronLau]

Hello,

Desktop audio capture on Linux works by configuring a virtual microphone. As far as I know, there's no way for a library like wavy or cpal to do this configuration in a cross-platform way. I've set it up using PulseAudio's pavuctl before, and then after setting it up, the desktop audio output shows up as a microphone in wavy.

[Fractal-Tess]

Is that also how open broadcast software works? I've always wondered what goes under the hood, but I feel like it is needlessly complicated for some reason. Still I would love it you were to give me a few pointers on where to look in order to learn more about this. I'll for sure check out pavuctl and what I can do with it.

[AldaronLau]

I Just did some research, and I think OBS talks to PulseAudio, JACK and Pipewire separately on Linux, which all have their own methods of exposing a loopback device. None of which are guaranteed to be installed on any given Linux machine.

For a portable solution, you should be able to set up ALSA loopback devices with this command (source):

sudo modprobe snd-aloop

Also this stackoverflow post I found has a little more information about audio loopback devices on Linux in the answers.

[Fractal-Tess]

That makes a lot of sense.

I actually succeeded in capturing desktop audio with the help of pavucontrol.
I haven't dug deeper into the rabbit hole, but it all seems very magical to me and I still do not understand what exactly is going on under the hood.
I'll try looking into it a bit more since I'm also trying to capture specific output streams as well.