Re: [LAU] jack: interface selection has no effect

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To: Max <abonnements@...>
Cc: A list for linux audio users <linux-audio-user@...>
Date: Monday, August 11, 2014 - 7:46 pm

On Mon, 11 Aug 2014, Max wrote:

Pulse on jack.

>> qjackctl expects (as installed) to use jackdbus.

It is a part of jackd2. Normally if you have jackd2 you also have

Then, if you use qjackctl to start jack first thing in the session before
you run anything else or start jackd through a script. Then whatever
device you have set up should get picked up by jackdbus. If you run
something that needs jack first, chances are it will start jackd for you
and once it is running, qjackctl has no control over it and can not stop
and restart it. My personal feeling is that debian/ubuntu etc. should
package jackd2 and jackdbus seperate so jackd is not available in a
jackdbus system to cause problems. A script that takes the same
commandline as jackd and then calls jack_control with the right parameters
could be included instead.

Using jackdbus, and installing pulseaudio-module-jack, should besides
installing module-jack-sink and module-jack-source also install
module-jackdbus-detect which will auto-load the other two modules for you
when jackdbus is detected as running.

Personally, I have a script like:

#! /bin/bash
# start jack and midi


#sleep $DELAY

jack_control ds $DRIVER dps device $DEV dps rate $RATE dps period $FRAME \
dps nperiods $PERIOD start

sleep $DELAY

a2jmidid -e &

sleep $DELAY

sleep $DELAY

pulseaudio -k


The last line restarts pulseaudio because upstart seems to think it has to
start pulse first :P And I don't want my system too far off stock because
I try to help those with a stock system. This gets started by:
But I could have put it in /etc/xdg/autostart for system wide use.

[Desktop Entry]
Comment=Jackdbus starter


jack_lsp shows:
... (the rest of my system listing skipped)
PulseAudio JACK Sink:front-left
PulseAudio JACK Sink:front-right
PulseAudio JACK Source:front-left
PulseAudio JACK Source:front-right
a2j:Midi Through [14] (capture): Midi Through Port-0
a2j:Midi Through [14] (playback): Midi Through Port-0
a2j:Ensoniq AudioPCI [16] (capture): ES1370
a2j:Ensoniq AudioPCI [16] (playback): ES1370

qjackctl is configured for the same card and start settings, the options
tab has Execute script on startup: pulseaudio -k and Execute script after
startup: a2jmidid -e &, but really I never use qjackctl to start and stop
jackd as it runs from session start to stop. I use qjackctl for the
patchbay (connections) and logging. In the Misc. tab I have qjackctl set
for Enable D-Bus interface and I have Stop JACK audio server on
application exit unchecked so that stopping qjackctl does not stop

I use this project:

To control jack latency on the fly and to disconnect pulseaudio if I think
it might interfere with what I am doing. It also sets the CPU governor and
allows me to stop cron so there is no sudden net/disk activity in the
middle of a take.

>From pavucontrol, on the Configuration tab, I set any audio card profiles
to "Off". I probably should just set pulse not to use the alsa-sink/sourse
modules, but so far I have been too lazy to do so.

In my opinion this is the proper way to get jack and pulse to play nice.

If one is using jackd1 Then everything changes because it is not dbus
controlable (at least out of the box, I hear there is a patch)

Then the link you have above can be used and qjackctl can have the D-Bus
interface turned off. However, there is more work to turn the pulse-jack
bridge off and on on the fly as there are two modules to (un)load. Also,
jackd has to be started with qjackctl if you wish to use that as the
controler. Unless you want to add:
Execute script on Shutdown: killall -9 jackd
To your qjackctl setup.

I can not recommend jackd2 or jackd1 as one being better than the other. I
think there are situations where one or the other shines. However, in the
case where pulse and dbus are already in use, I would choose jackdbus as
the most compatible version of jack to use. I do not know if jackd can
safely be removed/-x/renamed or not when using jackdbus... that is
something I should experiment with though :)

Len Ovens

Linux-audio-user mailing list

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Messages in current thread:
Re: [LAU] jack: interface selection has no effect, Len Ovens, (Sat Aug 9, 6:58 pm)
Re: [LAU] jack: interface selection has no effect, Len Ovens, (Mon Aug 11, 7:46 pm)
Re: [LAU] jack: interface selection has no effect, Len Ovens, (Tue Aug 12, 2:57 am)
Re: [LAU] jack: interface selection has no effect, Len Ovens, (Mon Aug 18, 6:57 am)