Proper way to automatically start fluidsynth and jackd (Raspberry Pi OS)

[mojca]

I have a simple arduino-based MIDI instrument connected to a Raspberry PI, running 64-bit Raspberry Pi OS based on Debian 12.
RPi is also connected to a PCM5120 and I followed these instructions to set it up.

I can launch two ssh shells to the RPi and run:

/usr/bin/jackd --timeout 2000 --realtime --realtime-priority 95 -d alsa --device hw:sndrpihifiberry --period 64 --nperiods 2 --rate 44100

followed by

fluidsynth --audio-driver=jack --midi-driver=alsa_seq --sample-rate=44100 --connect-jack-outputs --audio-channels=2 -is /usr/share/sounds/sf2/my_own_sound_font.sf2

in the second shell. This way I can get very low latency when playing the midi instrument.

However I don't seem to be able to figure out how to automatically start any of the two (jackd or fluidsynth) via systemd or via some other equivalent mechanism that would let me start the MIDI synthesis automatically.

I first managed to get the low latency working on Patchbox OS by running Qsynth, but I would like to get it working on barebone minimal Debian running in headless mode, without any UI.

I saw that Patchbox has something similar to the following contents in /etc/jackdrc (below I wrote the options that I though I needed myself):

$ cat
#!/bin/sh
# exec is used to 'morph' the shell interpreter process into jackd process, saving some system resources.
exec /usr/bin/jackd -v --timeout 2000 --realtime --realtime-priority 95 -d alsa --device hw:sndrpihifiberry --period 64 --nperiods 2 --rate 44100

If I don't start jackd upfront, fluidsynth does seem to attempt starting jackd, but something weird starts going on. In particular I don't quite understand exec of JACK server (command = "#!/bin/sh") failed: No such file or directory. And Cannot connect to server socket err = No such file or directory also doesn't help me much.

$ fluidsynth --audio-driver=jack --midi-driver=alsa_seq --sample-rate=44100 --connect-jack-outputs --audio-channels=2 -is /usr/share/sounds/sf2/my_own_sound_font.sf2
FluidSynth runtime version 2.3.1
Copyright (C) 2000-2022 Peter Hanappe and others.
Distributed under the LGPL license.
SoundFont(R) is a registered trademark of Creative Technology Ltd.

fluidsynth: warning: No preset found on channel 9 [bank=128 prog=0]
fluidsynth: Connection of Midi Through Port-0 succeeded
fluidsynth: Connection of Arduino NANO 33 IoT MIDI 1 succeeded
Cannot connect to server socket err = No such file or directory
Cannot connect to server request channel
exec of JACK server (command = "#!/bin/sh") failed: No such file or directory
Cannot connect to server socket err = No such file or directory
Cannot connect to server request channel
Cannot connect to server socket err = No such file or directory
Cannot connect to server request channel
Cannot connect to server socket err = No such file or directory
Cannot connect to server request channel
Cannot connect to server socket err = No such file or directory
Cannot connect to server request channel
Cannot connect to server socket err = No such file or directory
Cannot connect to server request channel
jack server is not running or cannot be started
JackShmReadWritePtr::~JackShmReadWritePtr - Init not done for -1, skipping unlock
JackShmReadWritePtr::~JackShmReadWritePtr - Init not done for -1, skipping unlock
fluidsynth: error: Failed to connect to Jack server.
Failed to create the audio driver. Giving up.

I tried starting jackd with a service like the one I found here, but there are two problems:

• /usr/bin/jack_control start completely ignores the parameters from /etc/jackdrc (I assume I need to configure jackd elsewhere?)
• /usr/bin/jack_control refuses to work when run as root, but adding User=myusername under [Service] doesn't seem to help either

Debian comes with a ready-made systemd file for fluidsynth. I can edit /etc/default/fluidsynth to pass the correct parameters, but I don't come much further until I'm able to figure out how to get the jackd working properly/automatically.

sudo systemctl enable /usr/lib/systemd/user/fluidsynth.service
sudo systemctl start fluidsynth.service

[derselbst]

Fluidsynth doesn't actively starts up jack. Merely Jack starts itself (I think there's an option to disable that, but fluidsynth hasn't set it). I don't know about the underlying magic and related Jack commandline logs you're seeing, sry.

Regarding fluidsynth, pls. verify that your /usr/lib/systemd/user/fluidsynth.service file is same (or similar) to ours:
https://github.com/FluidSynth/fluidsynth/blob/bd04f3f6c81a114f3ad52c8e29be3b44dccd010f/fluidsynth.service.in

The line that starts with ExecStart is crucial. You'll notice a few environment variables in that line, that you can populate via EnvironmentFiles with our favorite fluidsynth options, like so:
https://github.com/FluidSynth/fluidsynth/blob/bd04f3f6c81a114f3ad52c8e29be3b44dccd010f/fluidsynth.conf.in

Usually, a system-wide and user-local EnvironmentFile exists. The exact location is also written in the .service file. It's up to you which to choose.

When done configuring, you should always start fluidsynth as a user-service:

systemctl enable --user fluidsynth.service
systemctl start --user fluidsynth.service

I would expect a similar setup procedure for the Jack Daemon (i.e. user service, EnvironmentFiles, etc.). But I have no idea how to configure jack + systemd properly.

[mojca]

Thank you very much for pointing me to the --user option. This is the one that I was in fact missing. Though I'm still unable to get everything working together.

I copied the following jackd service file from somewhere. I suspect it's not entirely correct, but at least I was now able to start it manually (after logging in via ssh) with the --user flag.

$ cat /usr/lib/systemd/user/jackd.service
[Unit]
Description=JACK 2
Before=sound.target
Before=pulseaudio.service
Requires=dbus.socket
After=usb-reset.service

[Service]
Type=dbus
BusName=org.jackaudio.Controller
ExecStart=/usr/bin/jack_control start
ExecStop=/usr/bin/jack_control stop
ExecStopPost=/usr/bin/pkill -9 jackdbus
SuccessExitStatus=0
RemainAfterExit=true
#Restart=always
#RestartSec=5

[Install]
WantedBy=sound.target

(I don't see anything corresponding to BusName=org.jackaudio.Controller inside /usr/share/dbus-1/)

$ systemctl --user status jackd.service
● jackd.service - JACK 2
     Loaded: loaded (/usr/lib/systemd/user/jackd.service; enabled; preset: enabled)
     Active: active (exited) since Wed 2024-01-03 19:01:22 CET; 9min ago
   Main PID: 1945 (code=exited, status=0/SUCCESS)
        CPU: 181ms

Jan 03 19:01:21 raspiccordion systemd[862]: Starting jackd.service - JACK 2...
Jan 03 19:01:22 raspiccordion jack_control[1945]: --- start
Jan 03 19:01:22 raspiccordion systemd[862]: Started jackd.service - JACK 2.

It does not work automatically after rebooting though, most likely because it's being started before DBus is ready.

$ systemctl --user status jackd.service
○ jackd.service - JACK 2
     Loaded: loaded (/usr/lib/systemd/user/jackd.service; enabled; preset: enabled)
     Active: inactive (dead)
$ journalctl --user -u jackd
Jan 03 21:12:12 raspiccordion systemd[862]: Starting jackd.service - JACK 2...
Jan 03 21:12:13 raspiccordion jack_control[2305]: --- start
Jan 03 21:12:13 raspiccordion systemd[862]: Started jackd.service - JACK 2.
Jan 03 21:16:19 raspiccordion systemd[862]: Stopping jackd.service - JACK 2...
Jan 03 21:16:19 raspiccordion jack_control[2707]: Traceback (most recent call last):
Jan 03 21:16:19 raspiccordion jack_control[2707]:   File "/usr/bin/jack_control", line 414, in <module>
Jan 03 21:16:19 raspiccordion jack_control[2707]:     sys.exit(main())
Jan 03 21:16:19 raspiccordion jack_control[2707]:              ^^^^^^
Jan 03 21:16:19 raspiccordion jack_control[2707]:   File "/usr/bin/jack_control", line 397, in main
Jan 03 21:16:19 raspiccordion jack_control[2707]:     bus = dbus.SessionBus()
Jan 03 21:16:19 raspiccordion jack_control[2707]:           ^^^^^^^^^^^^^^^^^
Jan 03 21:16:19 raspiccordion jack_control[2707]:   File "/usr/lib/python3/dist-packages/dbus/_dbus.py", line 209, in __new__
Jan 03 21:16:19 raspiccordion jack_control[2707]:     return Bus.__new__(cls, Bus.TYPE_SESSION, private=private,
Jan 03 21:16:19 raspiccordion jack_control[2707]:            ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
Jan 03 21:16:19 raspiccordion jack_control[2707]:   File "/usr/lib/python3/dist-packages/dbus/_dbus.py", line 99, in __new__
Jan 03 21:16:19 raspiccordion jack_control[2707]:     bus = BusConnection.__new__(subclass, bus_type, mainloop=mainloop)
Jan 03 21:16:19 raspiccordion jack_control[2707]:           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
Jan 03 21:16:19 raspiccordion jack_control[2707]:   File "/usr/lib/python3/dist-packages/dbus/bus.py", line 120, in __new__
Jan 03 21:16:19 raspiccordion jack_control[2707]:     bus = cls._new_for_bus(address_or_type, mainloop=mainloop)
Jan 03 21:16:19 raspiccordion jack_control[2707]:           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
Jan 03 21:16:19 raspiccordion jack_control[2707]: dbus.exceptions.DBusException: org.freedesktop.DBus.Error.NoReply: Did not receive a reply. Possible causes include: the remote application did not send a >
Jan 03 21:16:19 raspiccordion systemd[862]: jackd.service: Control process exited, code=exited, status=1/FAILURE
Jan 03 21:16:19 raspiccordion systemd[862]: jackd.service: Control process exited, code=exited, status=1/FAILURE
Jan 03 21:16:19 raspiccordion systemd[862]: jackd.service: Failed with result 'exit-code'.
Jan 03 21:16:19 raspiccordion systemd[862]: Stopped jackd.service - JACK 2.

I tried to come up with something by following https://stackoverflow.com/questions/31702465/how-to-define-a-d-bus-activated-systemd-service, but I must have messed up completely.

If I start the above jackd service manually, then the combination with

$ cat ~/.config/fluidsynth
SOUND_FONT=/usr/share-sounds/sf2/my_own_sound_font.sf2
OTHER_OPTS='--audio-driver=jack --midi-driver=alsa_seq --sample-rate=44100 --gain=0.2 --connect-jack-outputs --audio-channels=2 -is'

and the service file that looks pretty much the same as your pointer seem to work fine.

(Initially I was getting fluidsynth: error: Failed to bind server socket: 98, but it turned out that I accidentally had another instance of fluidsynth started up automatically from /etc/rc.local as a "leftover from earlier attempts".)

So it seems that I'm only missing a way to properly start jackd now.

After you explicitly pointed me to the service file for fluidsynth, I noticed pipewire.service (I believe this is present out-of-the-box on Debian 12, but it wasn't in an earlier version of Debian). It looks like pipewire could be a replacement for jackd. I followed https://wiki.debian.org/PipeWire#Debian_12 and ran

sudo apt install wireplumber
systemctl --user --now enable wireplumber.service

but I would have to figure out how to get it working with fluidsynth as it complained about missing support for pipewire. I tried replacing --audio-driver=jack with --audio-driver=pipewire, but:

fluidsynth: error: Couldn't find the requested audio driver 'pipewire'.

The advantage would be the the service file for wireplumber already ships with the system (I trust it a lot more) and seems to be started correctly, while the jackd service file is most likely not written correctly, and the jack_control command also behaves in a somewhat weird way (it ignores the settings inside /etc/jackdrc, it is supposed to take care of starting jackd once, but it doesn't know in case it has already been started via some other way, etc.).

(On a second micro SD card we installed the fully blown OS. By configuring auto-login into the GUI and by starting Qsynth automatically after login, we do get the desired result with both jackd and fluidsynth being properly started by Qsynth in the background, without configuring any services whatsoever. But I don't particularly like all the extra overhead, and it also significantly prolongs the time needed between starting the device and being ready to play music.)

[derselbst]

I can't say anything about your jack and systemd problem, sry.

fluidsynth: error: Couldn't find the requested audio driver 'pipewire'.

That error indicates that fluidsynth was compiled without pipewire support (i.e. without libpipewire-dev being installed when compiling fluidsynth). You can either report this limitation to the package maintainer of your distro, or compile fluidsynth yourself locally.

[mojca]

I now found an excellent article explaining some details of DBus:

• https://www.baeldung.com/linux/systemd-session-dbus-headless-setup

By following this article I was finally able to get to a working system. I did multiple things, but probably the most relevant part was enabling auto-login:

loginctl enable-linger user

adding

if test -z "$DBUS_SESSION_BUS_ADDRESS"; then
    # Only start D-Bus if it's not already running
    eval `dbus-launch --sh-syntax --exit-with-session`
fi

to .profile, maybe adding some [Install] targets to existing systemd services, and finally here's the version of /usr/lib/systemd/user/jackd.service that I ended up using successfully (I was missing a bunch of ExecStartPost commands, since jack_control ignores /etc/jackdrc):

[Unit]
Description=JACK 2
Before=sound.target
Requires=dbus.socket
After=usb-reset.service

[Service]
Type=dbus
BusName=org.jackaudio.Controller
ExecStart=/usr/bin/jack_control start
ExecStartPost=jack_control ds alsa
ExecStartPost=jack_control dps device hw:0,0
ExecStartPost=jack_control dps period 64
ExecStartPost=jack_control dps nperiods 2
ExecStartPost=jack_control dps rate 44100
ExecStop=/usr/bin/jack_control stop
ExecStopPost=/usr/bin/pkill -9 jackdbus
SuccessExitStatus=0
RemainAfterExit=true
Restart=on-failure
RestartSec=5

[Install]
WantedBy=sound.target

And in any case the --user flag was the crucial one to enable and run both services (thank you very much for that hint):

systemctl --user enable /usr/lib/systemd/user/jackd.service
systemctl --user enable /usr/lib/systemd/user/fluidsynth.service
systemctl --user start jackd
systemctl --user start fluidsynth