Re: [LAU] What happens (or not) if one use the active d-bus interface option in QjackCtl ?

On Sat, 10 Oct 2015, fred wrote: dbus options with jack are to do with jack2. There is a patch to allow jack1 to be dbus controllable as well, but I don't know that any distos ship it and Qjackctl is not designed for it. jackdbus is the same jackd with the ability to use dbus to control it's operation. The advantage of this is that more than one program can interact with jackdbus. With jackd, only the program that starts it can stop it and the parameters can only be set at start time (with the exception of buffers which can be changed during run). With jackdbus, all parameters can be changed including audio device during runtime and can be changed by any program that can find the same dbus server (anything started since session startup). This means Qjackctl can be used to start jackdbus and then jack_control can be used to stop or maodify parameters. I think what stops people from making more use of jackdbus is that all the documentation and help for jack is with jackd command lines. So the new comer will be flooded with advice that shows how to use jackd and not jackdbus. To start jackd with default parameters (whatever was used last time) on the command line: jackd or: jackd & to start jackdbus: jack_control start To stop jackd the controlling terminal can use control c or if it was started with the & then you have to: killall -9 jackd With jackdbus: jack_control stop A typical jackd start line with parameters would be: /usr/bin/jackd -p1024 -dalsa -dhw:M66 -r48000 -p1024 -n2 The same thing in jackdbus might be: jack_control ds alsa dps device hw:M66 dps rate 48000 dps period 1024 \ dps nperiods 2 start or (if it is easier in a script): jack_control ds alsa jack_control dps device hw:M66 jack_control dps rate 48000 jack_control dps period 1024 jack_control dps nperiods 2 jack_control start Now to change the device without stopping jackdbus: jack_control dps device hw:AudioPCI sm An interesting side note: I have the AudioPCI installed only so I can use its MIDI port. The MIDI port is available no matter which device is set with jackd/bus. I use a2j_control to bridge alsa MIDI to jack MIDI (a2j_control ehw start). Documentation: Very little. man jack_control gives nothing, but jack_control on it's own with give a usage message (or jack_control help). I went through using the "get" commands to find out more. Jack_control is written in python and so: less /usr/bin/jack_control will allow one to see what dbus commands jack_control is sending to dbus to control jackdbus. Qjackctl does not at this time (maybe never) allow changing the jack server parameters on the fly. However, a jackdbus server started with qjackctl can be changed from command line with jack_control. Jackdbus works much more smoothly and automatically with Pulseaudio and the pulse-jack bridge. Pulse can be bridged to jackd (1 or 2) manually as well, but it requires an extra script to be run each time jackd is started. Depending which version of qjackctl you have (mine is older), it sets port-max lower (1024) than default (2048) and can not be set higher. Most desktops have no reason to run any lower than default. Embedded systems with limited memory might need something smaller... but probably also won't run qjackctl :) I know this is much more than the qjackctl side of jackdbus, but it does give some of the why too. -- Len Ovens www.ovenwerks.net