PulseAudio switch-on-connect and device-manager modules

[David Rosca]

On Wed, Mar 21, 2018 at 4:51 PM, Nate Graham <nate at kde.org> wrote:
> Howdy folks,
>
> It seems that we have KCMs that conflict with one another:
> - The Phonon Audio/Video KCM uses the module-device-manager PulseAudio Module.
> - plasma-pa's KCM has an "Automatically switch all running streams when a new output becomes available" checkbox that loads the switch-on-connect PulseAudio module.
>
> ...But both modules can't be loaded at once. So plasma-pa's "Automatically switch all running streams when a new output becomes available" checkbox does not work in many circumstances.
>
> This is all relevant to our users who would like to have audio streams automatically switched over when a new device becomes available (e.g. a bluetooth or USB headset) and report that checking the "Automatically switch all running streams when a new output becomes available" checkbox doesn't enable that behavior for them.
>
> What's our path forward here?

As already said by David Edmundson, it works correctly.

Just to make it clear, this is what those two modules are doing:

module-device-manager allows to configure which device will be used
for given stream according to its role (what type is it, specified by
applications - eg. notifications, music, video, ...), but this only
works for existing (or already seen) devices.

module-switch-on-connect basically just switches all streams to newly
connected devices

As they both change devices for streams, they can't coexist without
producing unexpected results. You can see that there is no clear
winner to which module we should load by default, device-manager
offers detailed configuration but doesn't handle new devices,
switch-on-connect offers no configuration but handles new devices as
expected. Ideally, we would want behavior of both modules, but that's
not possible. module-device-manager is loaded by default and also
existed before module-switch-on-connect, so I think we shouldn't
change that. Users can still choose to use switch-on-connect (using
checkbox in plasma-pa kcm) if they want.

David


>
> Nate
>
>
> Relevant bug reports, for background:
> - https://bugs.kde.org/show_bug.cgi?id=392103
> - https://bugs.kde.org/show_bug.cgi?id=392117
> - https://bugs.freedesktop.org/show_bug.cgi?id=95104
> - https://bugs.launchpad.net/ubuntu/+source/pulseaudio/+bug/1720519
>