Real-time scheduling not permitted with JACK

I’m running into the real-time scheduling issue with JACK (operation not permitted).

Specifically, the console logs the following when trying to start a session in Ardour:

Log Messages:
ERROR: JACK: Cannot use real-time scheduling (RR/5) (1: Operation not permitted)
ERROR: JACK: JackClient::AcquireSelfRealTime error
INFO: Loading menus from /etc/ardour6/ardour.menus
ERROR: JACK: Cannot create thread res = 1

I did choose “Yes” for real-time priority when installing jack, and QJackCtl starts the jack server with “real-time” checked, so it seems the issue is with Ardour.

I’ve followed various instructions about setting real-time priority values in several different daemon *.conf files and added myself as a user to the audio group… all to no avail.

This error is from JACK, not from Ardour. It’s hard to answer this question without knowing a lot more about which Linux distro you are using, and precisely what you’ve already tried.

Currently using Ubuntu 21.10, kernel 5.15.13

Created /etc/security/limits.d/audio.conf with the following contents:

# Provided by the jackd package.
#
# Changes to this file will be preserved.
#
# If you want to enable/disable realtime permissions, run
#
#    dpkg-reconfigure -p high jackd2

@audio   -  rtprio     95
@audio   -  memlock    unlimited
#@audio   -  nice      -19

Changed the following line in /etc/pulse/daemon.conf:

; rlimit-rtprio = 15   #previous value = 9

Made changes according to advice in the following link:
https://linuxmusicians.com/viewtopic.php?t=17718

Have you rebooted or logged out and back in since?
Existing user session will not be granted new permissions.

It may still fall back to non-realtime, check qjackctl’s Log window.