[LAU] jack, pulse = confusion, at least for me

Mac ussndmac at charter.net
Mon Mar 13 18:24:35 UTC 2017

Ok, so since I have done nothing to change anything from a default UBStudio
16.04, then I should be able to assume I'm working with jackd2.

If I understand your reply, dbus provides some magic that allows pulseaudio
(as installed with UBS16.04) to see when a jackd2 server is started and
create the pulseaudio source/sinks.

and the ds... arguments start the alsa source/sinks

Having just tried it, "jack_control start" from the command line starts
jack and pulse does indeed connect auto-magically. (jackd on the command
line does not).
And it starts jack with the last configuration started. (On this PC that's
firewire, not alsa, I assume it would be the same on my alsa/usb PC, i.e.
starting the last configuration used.)

...the fog begins to clear. ;)


On Sat, Mar 11, 2017 at 3:09 PM, Len Ovens <len at ovenwerks.net> wrote:

> On Sat, 11 Mar 2017, Mac wrote:
> I'm running multiple PC's with UbuntuStudio 16.04.
>> I'm trying to figure some differences in what happens between the PC's
>> when jack
>> is started.
>> Questions:
>> - what is the process of determining what combination of jackd, jackdbus,
>> jack1,
>> jack2 is actually being run from the command line or from qjackctl?
>> - since starting jack from the command line doesn't result with a pulse
>> source/sink, but starting it from qjackctl does end up with pulse
>> source/sink and
>> system source/sink? (And, how do I duplicate what happens when jack is
>> started
>> from qjackctl from the command line?)
> UbuntuStudio comes with jackd2 by default (same as debian) it can be
> changed over to jackd1, but just installing jackd1 will remove lots of
> audio SW that depends on jackd2. so the uninstall of jack2 has to happen
> without touching the deps and the install of jackd1 needs to happen the
> same way. I don't know the commands off hand.
> The jackd2 package comes with both jackd and jackdbus. By default qjackctl
> will work with jackdbus. The dbus interface is required in order for the
> pulseaudio module to autoconnect to jack. It is possible to manually
> connect pulse to jackd without the dbus part of jack.
> The best way to control jackdbus from the commandline is to use
> jack_control. jack_control comes with pretty much zero documentation...
> just run jack_control with no options for usage output.
> jack_control start
> will start jack with saved parameters
> jack_control ds alsa dps device hw:D66 dps rate 48000 dps period 128 \
> dps nperiods 2 start
> will start with new parameters. It is easy to split commands across more
> than one line if desired. I normally run:
> jack_control ds alsa dps capture none dps playback none
> first because qjackctl seems to set capture and playback separately even
> for the same device and that resets it.
> All of these parameters can be changed on the fly without stopping jack.
> Just put in the changes you want (devices, rate, latency, etc) and then
> enter:
> jack_control sm to make the switch. While jack may survive switching rate
> while running, most clients probably won't... latency switching even though
> it is possible on a running jack1 as well does not work with all clients
> either... but most do. Switching devices is fine so long as they have the
> same number of ports... well connections to system ports will get dropped
> and need reconnecting anyway. (there are utilities that will do this for
> you, check if jack-tools is installed)
> --
> Len Ovens
> www.ovenwerks.net
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