Re: Combine 2 hardware devices into 1 sndio device

From: Alexandre Ratchov <>
Date: Fri, 2 Aug 2019 11:28:44 +0200
On Fri, Aug 02, 2019 at 03:14:59PM +1000, Tim Preston wrote:
> Hi,
> Is it possible to combine or merge two hardware devices into a
> single sndio device?
>  My use case is a USB webcam with mic, and an external USB audio
> interface for my headphones. When making video calls in Firefox or
> Chromium I can use either the mic or headphones, but not both at the
> same time. Both web browsers use the 'default' audio device (snd/0)
> and don't list any other devices to choose from.
> Since this is a FreeBSD system one thing I can do is attach sndiod
> to the mic and expose that as snd/0, then let audio out fallback to
> FreeBSD's default (which I can set as the USB audio interface). This
> means the audio out is not controlled by sndiod, and is hence quite
> loud.  Thanks, Tim


Sorry, it's not possible to combine multiple devices into a single
one, mostly because they run at slightly different clock rates and
it's difficult to synchronize them reliably.

To handle telephony programs, the plan is to let programs not using
full-duplex (like firefox and chromium) to choose different devices
for playback and recording, but that's not done yet, no promises. In
other words "default" would point to different devices depending on
whether it's open play-only, rec-only or full-duplex.
Received on Fri Aug 02 2019 - 11:28:44 CEST

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