Selecting a specific microphone input from a USB audio interface (multichannel device)

[mrjulius]

I'm using a professional audio interface with multiple microphone inputs. How can I select a specific microphone input in OBS? In the source properties, you can select the device, but not the individual channels. It looks to me that OBS does not support multichannel devices, am I right?

(Tested with RME Babyface Pro and Behringer UMC1820)

There's probably tons of others who have wondered the same. Have you found any solutions for this?
My only idea would be to capture the microphone with some other DAW like Reaper, and try routing it to OBS via alsa loopback device.

 

[AaronD]

You don't. It's one of my annoyances with OBS too. You can only select the device, not specific channels, and OBS mixes-down the entire device to mono, stereo, 5.1, whatever it's set to, before it lets you do anything with it.

I figured that out with a digital console and a live band. Fortunately, I could go into the console's settings and make all of the other USB tracks silent, but that's not always an option.

It's technically possible to split a 2-ch interface into dual mono's, but they're still not separated completely (Filters on either one probably still respond to both):

1. Copy the stereo source twice (4 channels total, for those who count stereo as 2)
2. Balance each copy hard to one side
3. Check the Mono box

This works because the mono and pan/balance are backwards from the way that most consoles have them. So now you have a center-panned mono signal for each of the 2 inputs of that one device. But you only have practical control of the volume and mute for each one.

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For your workaround to use a DAW and a loopback, yes, that's the only way I know too. The loopback has the same limits as any other source in OBS - entire device only, mixed-down to OBS's channel count before any user settings - but you can control that!

Generally, that's the way to handle audio anyway, beyond the basic bedroom-stream hobby. Do all of your audio processing outside of the video compositor, whatever you use to do either one, and bring in the finished soundtrack to pass through unchanged.