USB microphones with FreeBSD-CURRENT

Graham Perrin grahamperrin at
Mon Mar 30 19:13:15 UTC 2020

On 28/03/2020 12:45, Jan Beich wrote:
> Graham Perrin <grahamperrin at> writes:
>> I can't get web browsers to recognise USB microphones.
>> USB output (e.g. to my headphones) is OK.
>> USB input (e.g. from the microphone part of the headphones) is not.
>> Any suggestions?
> Firefox uses "pulse-rust" cubeb backend *by default* if "pulseaudio"
> package is installed. getUserMedia is supposed to preset a dropdown menu
> to select a microphone. Make sure pulseaudio actually recognizes the
> desired microphone e.g., debug via "pactl list" and "parec".
> I don't have a mic but, looking at the code, only pulse-rust or pulse
> backends on Linux/FreeBSD support selecting non-default audio device.
> It maybe possible to use other backends but if audio device used for
> output and input are different that'd require routing defaults which can
> be done via config file (e.g., ~/.asoundrc) or externally via virtual_oss.
>> pcm3: <USB audio> (play/rec) default
>> pcm4: <USB audio> (rec)
> Are these distinct physical devices?


>> hw.snd.default_unit: 3
> Have you tried using 4?

I did, but decided that the device previously at 4 (Alctron USB700 
<>) probably 
has a hardware fault.

Worth noting: if I attempt to suspend the system whilst the device at 3 
(SteelSeries Siberia 350 headphones with integral microphone 
<>) is physically 
connected, suspend sometimes fails; it becomes necessary to force off 
the computer.

If I start the system with the headphones connected, then the microphone 
at 3 is usable at e.g. 
<> and 
<> (see <>) but not in 
Microsoft Teams.

If I disconnect the headphones (to minimise the risk of failure to 
suspend), then reconnect, the system seems unable to reuse the 
headphones (see <>); a restart is required.

In Microsoft Teams, neither 2 nor 3 is detected; there's only 1 (see 
<>) and after allowing use of /dev/dsp1 
it 'disappears', leaving only the camera in use (head of 

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