[pulseaudio-discuss] Why does Jack section uses "state.plugged = unknown" and "state.unplugged = unknown"?

[Tanu Kaskinen]

On Fri, 2021-09-17 at 11:41 +0800, Chengyi Zhao wrote:
> Hi guys,
> 
> I don't know why Jack section uses "state.plugged = unknown" and 
> "state.unplugged = unknown" in the path file 
> "analog-output-lineout.conf" below.
> 
> I think PulseAudio should set Jack to be available when it recognizes 
> the "Jack Line Out CLFE" is plugged, and vice versa.
> 
> Would you please help explain the true meaning of ”unknown“ here.
> 
> [Jack Line Out CLFE]
> state.plugged = unknown
> state.unplugged = unknown
> required-any = any

The center/LFE channel alone isn't a good source for lineout
availability information, so we ignore it for that purpose. If you have
only center/LFE connected but not the front channels, neither stereo
nor surround output is really functional. If you don't have center/LFE
connected, the path may or may not be functional, depending on whether
you're using stereo or surround.

If we had separate lineout path configurations for stereo and the
various surround profiles, then we could perhaps use "state.unplugged =
no" to mark the surround output unavailable when center/LFE isn't
connected.

-- Tanu