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

[Tanu Kaskinen]

On Thu, 2014-10-09 at 00:39 +0200, Mark Gaiser wrote:
> On Wed, Oct 8, 2014 at 1:06 PM, Tanu Kaskinen
> <tanu.kaskinen at linux.intel.com> wrote:
> > On Mon, 2014-10-06 at 19:47 +0200, Mark Gaiser wrote:
> >> Ok, i tried a bunch of different players. The results:
> >> - mplayer (smplayer as well) : sound doesn't switch when attaching
> a headphone
> >> - rhythmbox : refused to play any plain simple mp3 file
> >> - amarok : sound doesn't switch when attaching a headphone
> >> - dragon player : sound doesn't switch when attaching a headphone
> >> ...
> >>
> >> I did get rhythmbox to beep once and that one came out of my
> headset.
> >> Based on that i'm beginning to think that there is some GTK vs Qt
> >> difference in play here.
> >>
> >> One thing i did found (in the kde settings) was that i can prefer
> my
> >> headphone to be first in sound order. Funny thing is, this is
> actually
> >> working for an application like amarok which then behaves as i
> expect.
> >> However, other apps don't seem that happy to comply and just spew
> out
> >> audio to my jack port.
> >
> > There shouldn't be that kind of differences between apps, unless you
> > have previously moved manually those applications around. What if
> you
> > clear the pulseaudio state by doing this:
> >
> > - disable autospawning (so that you can be sure pulseaudio isn't
> running
> > during the next steps):
> >     cat "autospawn = no" >> ~/.config/pulse/client.conf
> >
> > - killall pulseaudio
> >
> > - remove all files under ~/.config/pulse except client.conf
> >
> > - restart pulseaudio:
> >     pulseaudio -D
> >
> > - load module-switch-on-connect:
> >     pactl load-module module-switch-on-connect
> >
> > Is there still a difference in behaviour between amarok and other
> > applications?
> >
> > Since you use kde, the routing may be a bit different than on my
> > machine, if you have module-device-manager loaded, and that might
> > explain the general problem of the automatic routing not working as
> > expected. When you start your kde session, module-device-manager
> gets
> > loaded. On gnome, for example, that module is not loaded by default.
> > Just restarting pulseaudio while the session is running should get
> rid
> > of module-device-manager, because it's only loaded when the session
> > starts, but you can of course always unload it with "pactl
> unload-module
> > module-device-manager". You can verify that the module is not loaded
> by
> > running "pactl list modules short". If module-device-manager isn't
> > listed, then it isn't loaded.
> >
> >> Could you perhaps test if you can get the same thing working under
> mplayer?
> >> mplayer -ao pulse <some_mp3_file>
> >>
> >> That is a quite simple test - easy to reproduce - and doesn't give
> me
> >> the expected result. I wonder how that works with you.
> >
> > Works fine.
> >
> > --
> > Tanu
> >
> 
> And reporting back with my findings.
> 
> First i verified if the module "module-device-manager" would be
> loaded. It's not so that's probably not an issue.
> Then i followed your steps and it - amazingly - worked! However, with
> a issue.
> 
> If i play a sound file (using mplayer as a test case) it:
> - plays from my speakers by default (OK!)
> - If i attach my (usb) headset the sound moves to the headset. Happy
> me :)
> - If i detach my usb headset again the sound isn't being played
> anywhere anymore. Attaching/detaching many more times doesn't help
> either.
> 
> I also think i know why it happens, just not a solution to the issue.
> If i type "pactl list short sinks" i get this output when my headset
> is not attached:
> 
> 0       alsa_output.pci-0000_01_00.1.hdmi-stereo
>  module-alsa-card.c      s16le 2ch 44100Hz       SUSPENDED
> 1       alsa_output.pci-0000_00_1b.0.analog-stereo
>  module-alsa-card.c      s16le 2ch 44100Hz       SUSPENDED
> 
> When i play a file the list changes:
> 
> 0       alsa_output.pci-0000_01_00.1.hdmi-stereo
>  module-alsa-card.c      s16le 2ch 44100Hz       SUSPENDED
> 1       alsa_output.pci-0000_00_1b.0.analog-stereo
>  module-alsa-card.c      s16le 2ch 44100Hz       RUNNING
> 
> So far so good. I have no HDMI devices attached that can play sound (a
> projector is attached. It can beam video, not audio :)
> 
> When attaching the headset i get:
> 0       alsa_output.pci-0000_01_00.1.hdmi-stereo
>  module-alsa-card.c      s16le 2ch 44100Hz       SUSPENDED
> 1       alsa_output.pci-0000_00_1b.0.analog-stereo
>  module-alsa-card.c      s16le 2ch 44100Hz       IDLE
> 7
> alsa_output.usb-Corsair_Components__Inc._Corsair_Vengeance_1500-00-C1500.analog-stereo  module-alsa-card.c      s16le 2ch 44100Hz       RUNNING
> 
> Note the added usb headset and it is running now. All perfectly fine
> thus far.
> But when i detach my headset the list becomes wrong:
> 
> 0       alsa_output.pci-0000_01_00.1.hdmi-stereo
>  module-alsa-card.c      s16le 2ch 44100Hz       RUNNING
> 1       alsa_output.pci-0000_00_1b.0.analog-stereo
>  module-alsa-card.c      s16le 2ch 44100Hz       SUSPENDED
> 
> 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".

-- 
Tanu