[pulseaudio-discuss] PulseAudio, switch audio output on device connection

[Tanu Kaskinen]

On Sun, 2014-10-19 at 13:20 +0200, Mark Gaiser wrote:
> On Sun, Oct 19, 2014 at 12:01 PM, Tanu Kaskinen
> <tanu.kaskinen at linux.intel.com> wrote:
> > On Thu, 2014-10-09 at 00:39 +0200, Mark Gaiser wrote:
> >> Note the hdmi sink is now suddenly playing the sound!
> >> I would expect the sink to continue device that was sitting idle, but
> >> somehow it picked the other device.
> >> Did i actually find a bug just now or is this also some magic setting
> >> that i can change somewhere?
> >
> > It's a bug (or an unimplemented feature, depending on your point of
> > view). I didn't try to reproduce this, but I speculate that this
> > happens, because at the time when module-rescue-streams notices that the
> > headset is going away, it would like to move the stream to the default
> > sink, but at that time the default sink is still the headset, so instead
> > of the default sink, module-rescue-streams uses some other heuristics
> > for choosing the sink where it moves the stream. When the headset
> > finally disappears, the analog sink becomes the new default, based on
> > different heuristics than what module-rescue-streams used.
> >
> > When you re-attach the usb headset, the move doesn't happen, because the
> > stream is not connected to the default sink, and
> > module-switch-on-connect only moves streams that are connected to the
> > default sink.
> >
> > While better automatic routing is very much in my interests, it's not
> > the highest priority right now, so I don't know when this will be fixed.
> > There was some talk last week about improving module-device-manager and
> > then enabling it by default. If someone is going to work on that, it
> > will quite likely fix this issue.
> >
> > As a workaround, you can set the HDMI card profile to "off".
> 
> Hi Tanu,
> 
> Thank you very much for the detailed description. To me it sounds like
> module-rescue-streams might have a bug then. Also,
> module-rescue-streams apparently moves the stream to my hdmi, but
> shouldn't that become the default then? I mean, that would make
> module-switch-on-connect work again on re-attaching cases.

I think we should refactor things so that module-rescue-streams would
use the same code for figuring out the target sink as what is used when
the new default sink is decided. I created a formal bug report:
https://bugs.freedesktop.org/show_bug.cgi?id=85488

> Or another way; Shouldn't module-rescue-streams only be invoked when a
> device actually disappeared? I mean, that would probably fix the
> stream moving back to the default stream and would also fix the
> re-attach case, right?

When the device actually disappears, streams connected to it get killed.
That's why module-rescue-streams has to act before the device actually
disappears.

-- 
Tanu