[pulseaudio-discuss] Support for buttons on USB headsets?

[Tanu Kaskinen]

On Fri, 2015-10-23 at 12:46 -0500, Pierre-Louis Bossart wrote:
> My USB headsets have mute, volume up and volume down buttons exposed 
> with an HID interface. When I use them with Ubuntu/PulseAudio nothing 
> happens.
> Wondering if this is not supported at all, if my config is broken or if 
> a manual setup is required as described in [1] - a basic workaround to 
> link keycodes and alsamixer. If PulseAudio had this information it could 
> do a much better job.
> Thoughts?
> Thanks,
> -Pierre
> 
> [1] https://help.ubuntu.com/community/PlantronicsUSBHeadsetControls

I don't know what the current state is for supporting USB headset
controls. I don't have such hardware myself. I haven't heard any
complaints for a long time, though, which would suggest that the
support is pretty good, but if that's the case, I don't know how that
is implemented. PulseAudio certainly has no special support for that
(there is module-mmkbd-evdev, but that's not used in the default
configuration).

My understanding is that desktop environments run some daemon that
monitors keyboard events, and when volume/mute events happen, they
control the volume/mute of the default sink in PulseAudio. If USB
headsets look like keyboards, and if they emit standard codes, I'd
expect the daemon to pick up those events as well, and control the
default sink. Maybe this works generally well enough that people don't
complain a lot, but obviously there's the problem that if the headset
isn't the default sink, the wrong sink gets controlled (and a mute
event should probably mute the mic, not the headset speakers; I don't
know if there's a separate mic-mute code defined). If the headset
controls do nothing for you, maybe the emitted codes are non-standard?

Connecting to the input device directly from PulseAudio has the problem
that input devices tend not to be readable by regular users.

-- 
Tanu