Devlog: Sonic Pi

Me documenting my issues installing sonic-pi on arch.

https://github.com/seanbreckenridge/sonic_pi_music

For context, I use pulseaudio, not alsa.

After running: yay -S sonic-pi

The default sonic-pi package from community failed to launch because of JACK errors; errorlog

JACK is running in realtime mode, but you are not allowed to use realtime scheduling.
Please check your /etc/security/limits.conf for the following line
and correct/add it if necessary:

  @audio          -       rtprio          99

After applying these changes, please re-login in order for them to take effect.

You don't appear to have a sane system configuration. It is very likely that you
encounter xruns. Please apply all the above mentioned changes and start jack again!
connect(2) call to /dev/shm/jack-1000/default/jack_0 failed (err=No such file or directory)

JACK is running in realtime mode, but you are not allowed to use realtime scheduling.
Please check your /etc/security/limits.conf for the following line
and correct/add it if necessary:

  @audio          -       rtprio          99

After applying these changes, please re-login in order for them to take effect.``

After adding that line to /etc/security/limits.conf and restarting, it errored with:

JACK is running in realtime mode, but you are not allowed to use realtime scheduling.

Your system has an audio group, but you are not a member of it.
Please add yourself to the audio group by executing (as root):
  usermod -a -G audio sean

So, I ran: sudo usermod -aG audio "$(whoami)"

Should be noted that the arch wiki says to instead manually add your user to the realtime group, but sonic-pi needs you to be running this manually, so, not going to do that.

After restarting:

$ groups
docker users video audio wheel

After that, running sonic-pi causes this error:

connect(2) call to /dev/shm/jack-1000/default/jack_0 failed (err=No such file or directory)
could not open driver .so '/usr/lib/jack/jack_net.so': libcelt0.so.2: cannot open shared object file: No such file or directory

could not open driver .so '/usr/lib/jack/jack_firewire.so': libffado.so.2: cannot open shared object file: No such file or directory

I use pulseaudio instead of alsa. Seems that JACK works better with alsa (i.e. it has a backend for it, see man jackd).

Doesn’t seem that there’s a jack daemon running in the background, not sure if there should be:

[ ~ ] $ ps -ef | grep jack
sean        1959    1934  0 11:14 pts/9    00:00:00 grep jack

I found the solution to this on this issue; which is to run jackd and qjackctl manually:

$ cat "$(which sonic-pi-run)"

#!/bin/bash

jackd -R -d alsa -d hw:1 &
qjackctl &  # (yay -S qjackctl)
# wait for jackd and qjackctl to be up
sleep 5
sonic-pi # block

# kill background jobs
kill -15 $(jobs -p)

If something is already using hw:1 (e.g. you have mpv playing some audio), this causes jackd to not be able to use hw:1, so it fails to acquire that, and sonic-pi fails with an error again.

Without qjackctl, it seems that this causes pulseaudio to break… ? and it becomes ‘dummy output’:

So, what I typically do is:

  • make sure I’ve used pulseaudio at least once since the computer has started (just play some song in mpv and then quit)
  • quit everything that is using pulseaudio actively
  • run sonic-pi-run (the script above)

And then, when I exit, pulseaudio takes back over.

Success!

Downsides:

  • Have to be a bit careful about mistakenly opening multiple instances of sonic-pi. If I open it and then quit quickly, something may have been acquired but not released, which causes pulseaudio to become ‘dummy output’, or jack to fail to acquire hw:1.
  • ‘breaks’ system audio/pulseaudio while sonic-pi is open, so its the only thing that can use audio

References: