[LAU] Scripting jackd connections

[Len Ovens]

On Wed, 15 Jun 2016, Will Godfrey wrote:

>> You probably really want to use jackdbus (what qjackctl on UbuntuSTudio
>> uses by default) so that you can change the system device the jack server
>
> I don't know about ubuntu, but here on vanilla debian, jackdbus is quite a
> headache for me.
>
> Something (I haven't discovered what) is starting it up, and it connects to
> onboard hdmi, if I then start qjackctl it sees jack running so doesn't apply
> the setting I actually want, which is my KA6. It happens just infrequently
> enough for me to forget and wonder why everything is connected but I'm getting
> no sound :(

Are you sure it is not the other way around? Normally it is jackd that 
gets started by some jack app and then qjackctl can no longer start 
jackdbus which is pretty normal. Does your version of jack happen to be 
from 2014ish? It was buggy and when an app started jackd in temporay mode 
it did not exit when the app closed.

qjackctl can only control an instance of jackd it starts itself. However, 
I can start jackdbus with jack_control and use qjackcontrol to stop and 
then restart with different parameters. If perhaps you are thinking that 
you often find "jackdbus auto" running using ps x or something like that, 
do try jack_control status

If it says:
--- status
stopped

jackdbus is not the problem.... probably jackd is also running... try
killall -9 jackd and see if qjackctl starts working as you expect.

You either need a working jackd or you can chmod -x /usr/bin/jackd if you 
don't want to do that. (I ran with jackd chmod -x for two years waiting 
for the repos to catch up with no harm. BTW, jackdbus can do pretty much 
anything jackd can using jack_control. Try it in a terminal with no 
parameter for a help list as there is no man page :P

--
Len Ovens
www.ovenwerks.net