jack-start.sh

#!/usr/bin/env bash

# Colors
C1='\033[1;32m' # Green
C2='\033[1;33m' # Yellow
C3='\033[1;31m' # Red
C4='\033[1;37m' # White
C0='\033[0m'    # No color
delay () { sleep "${1:-1}"; }

#
# Start JACK server
#
# JACK will be serving our soundcard and all its wirings.
# This soundcard however should be taken out of the PulseAudio control.
# Add corresponding ignore rules into /etc/udev/rules.d/* to achieve this. 
# @see: https://jamielinux.com/blog/tell-pulseaudio-to-ignore-a-usb-device-using-udev/

echo -e $C1"Starting JACK"$C0
delay

# First lets find and kill of the instances jackd and jackdbus
killall -9 jackd
killall -9 jackdbus
delay

# Now it's time to start our own new and shiny Jack2
# I use an external mixer device (Yamaha AG03) connected via USB
jackd -ndefault -dalsa -dhw:AG06AG03 -r44100 -p256 -n3 &
JACK_PID=$!
delay 5

#
# Load PulseAudio modules
#

# First let's disable PulseAudio JACK autodetection module which creates sinks/sources 
# automatically. Instead we're gonna create them manually in a moment.
pactl unload-module module-jackdbus-detect

# Now let's create our sinks/sources. They're gonna function as bridges 
# between PulseAudio and JACK worlds. So I call them just cables.
# The outputs will be saved into variables to unload modules later on.

echo -e $C1"Creating virtual cables"$C0
delay

# Sinks are the PulseAudio outputs (Speakers) i.e. where you can stream audio from your 
# music player or a web-browser for example
pactl load-module module-jack-sink client_name=Cable1 channels=2

# Sources are the PuleAudio inputs (Mics) i.e. from where you can record audio with  
# PulseAudio compatible programs as OBS, Audacity and etc.
pactl load-module module-jack-source client_name=Cable2 channels=2
pactl load-module module-jack-source client_name=Cable3 channels=2


#
# Wiring
#

echo -e $C1"Wiring up"$C0
delay

# We're gonna wire things up now using Qjackctl PatchBay feature.
# For this to happen you first need to create PatchBay configuration.

# Let's use a constant with the path to your PatchBay configuration.
PATCHBAY=patchbay.xml

[[ "$1" == "config" ]] && {
  qjackctl
  delay
  echo -e $C3"Shutting down jackd"$C0
  delay
  kill ${JACK_PID}
  delay
  echo -e $C2
  echo -e "If you have finished editing the patchbay configuration file $C4${PATCHBAY}$C2"
  echo -e "restart this script w/o ${C4}config$C2 option and you're done."
  echo -e $C0
  exit 1
}

[[ -f ${PATCHBAY} ]] || {
  echo -e $C2
  echo -e "The patchbay configuration file $C4${PATCHBAY}$C2 not found."
  echo -e "Please re-run this script with ${C4}config$C2 argument to run qjackctl."
  echo -e "There should you create a PatchBay configuration and export to this"
  echo -e "directory with the name: $C4${PATCHBAY}$C2"
  echo 
  echo -e "Please don't run ${C4}qjackctl$C2 manually, instead - let this script do this"
  echo -e "for you, because to this point jackd should be running and cables are created."
  echo -e $C0
  delay

  echo -e $C3"Shutting down jackd"$C0
  delay
  kill ${JACK_PID}
  delay
  exit 1
} 

#echo qjackctl -a ${PATCHBAY}