[LAU] Getting Rhythmbox to Appear in qjackctl

[Len Ovens]

On Wed, 20 May 2020, Samir Parikh wrote:

> How do I get Rhythmbox (GNOME application similar to iTunes) to appear 
> in qjackctl?

Rythumbox must have the ability to open as a jack client built in. 
Therefore, the place to check would be in the 
setting/preferences/options/whatever dialog and see if it is possible to 
set audio out to jack

> Over the past few days, I have been doing more research, reading wiki 
> pages and watching YouTube videos to become more familiar with JACK and 
> the various tools.  Thus far, I have:
>
> - installed qjackctl and its dependencies on Ubuntu 16.04

16.04 is kinda old, the version of jack in ubuntu20.04 has had some 
important bug fixes.

> - installed pulseaudio-module-jack

This package comes with three modules:
  - module-jackdbus-detect
 	This module will be loaded by default on pulse startup. if it
 	detects that jackdbus (from jackd2) is running it will load two
 	the two other modules below. In my case I unload this module
 	at session startup and load the other two modules via script.

  - module-jack-source
 	This module creates a bridge from Jackd to Pulse. I load these by
 	script because I can set their name, channel count, etc. More
 	than one of these can be run at a time if you wish to feed two or
 	more inputs from jack to pulse. In your case you want one only
 	which you can call jack-mic for example.

  - module-jack-sink
 	This module creates a bridge from Pulse to Jackd. I load these
 	from script as well... for the same reasons. More
         than one of these can be run at a time if you wish to take the
 	outputs of more than one Pulse application and mix them in jack.
 	In your case, you can have one of these called jack-out for
 	feeding to the system output (speakers or headphones) and
 	another one called Rhythmbox-out. On your jack graph in
 	qjackctl you can connect this to pulse-in as well as
 	connecting system_1 and system_2 to pulse-in. You would then
 	have a mix of the mic and Rhythmbox showing up as a mic in.
 	do remember to use pavucontrol to set Rhythmbox's output to
 	the Rhythmbox-out sink (Rhythmbox may allow you to set this
 	up in it's settings so you only have to do this once instead
 	of each time) You would use the mic level in pavucontrol
 	to set the mic level and the output level control of
 	Rhythmbox to set how much of that signal is added to the mic
 	level. Changing the mic level will change both.

There are in ubuntu 16.04, both jackmixer and idjc which will both be able 
to act as a mixer with this setup allowing setting each level separately 
and offer more control. neither one of these applications are available in 
ubuntu 20.04 due to libs they rely on being deprecated. I am hopeful they
will be re-added in the future (but am not holding my breath). zita-mu1 
may also work for you as a mixer. A plugin wrapper like Carla could be 
used to provide level and eq control as well (or jack client versions of 
plugins for that matter)


--
Len Ovens
www.ovenwerks.net