[pulseaudio-discuss] Jack-sink and pavucontrol .. who's on first!?

Tanu Kaskinen tanu.kaskinen at linux.intel.com
Thu Jun 6 03:24:46 PDT 2013

[Added pulseaudio-discuss back to CC.]

On Wed, 2013-06-05 at 11:10 -0600, Bearcat Şándor wrote:
> Here's what happens. If i just log-in with out these scripts enabled
> pulseaudio and jack startup fine together, as i have jack in my autostart
> list in gnome.

Uh, OK. So pulseaudio and jack start in an undefined order, but it looks
like usually pulseaudio starts first, because if it was the other way
around, I think you wouldn't see the alsa card in pulseaudio.

> If i start gnome normally with the scripts enabled, i get only the
> jack-sink listed in my devices and i can start and stop jack as i please,
> but i only ever get the jack-sink listed by pulse.

Yes, that's expected, because we don't currently (properly) support the
scenario where jack is already running when pulseaudio starts.

> If i have the scripts disabled and start and stop jack i see:
> ATTENTION: The capture device "hw:0" is already in use. The following
> applications are using your soundcard(s) so you should check them and stop
> them as necessary before trying to start JACK again:
> pulseaudio (process ID 3423)
> jackdbus (process ID 11469)
> Fri May 31 15:12:24 2013: Jack: JackDriver::Close

What's the output of "lsof /dev/snd/*"? I suppose pulseaudio is only
using the /dev/snd/controlC* files, and jackdbus is using /dev/snd/pcm*
files. If so, then pulseaudio isn't preventing jack from running, even
if it's listed in that error message. I suspect jackdbus is having a
stream open to the sound card.

My understanding is that jackdbus is the "D-Bus enabled" version of
jackd. Both jackd and jackdbus are full jack servers. So the error
message indicates that you're trying to start a jack server while a jack
server is already running. It seems like you didn't shut down jack
properly. (Don't ask me what "properly" means, I don't really know how
jack is supposed to be used.)

> What i'm wondering is why is the jack-sink being chosen as the default
> 'soundcard' by pulse and were/how can i change that? Is it just picking the
> first one? If i hit F6 to list my soundcards in alsamixer i see "default"
> and " 0 xonar st"  The "xonar st" is my soundcard and the "default" is the
> jack-sink. This need to be swapped.

alsamixer works in the alsa domain. "default" means pulseaudio, "xonar
st" means direct access to the sound card, bypassing pulseaudio. Your
goal is not to swap the order in which alsamixer lists the devices, your
goal is to make the xonar card visible in pulseaudio.

> There are times when pauvcontrol and
> gnome mixer don't even see my xonar st and only see the jack-sink.

The gnome mixer uses pulseaudio to access the sound devices, so if
pulseaudio didn't have access to the xonar card when pulseaudio started,
the xonar card won't be visible to clients, including the gnome mixer.


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