running audacity crashes jack

Manjaro linux current as of 29/6/2020 with kernel 5.6.16-1-MANJARO #1 SMP PREEMPT and NVIDIA modules 440.82
audacity 2.4.2 from flatpak
jack2 1.9.14-1

I have a problem. Let me state up front that I’m pretty sure it is not audacity’s fault, but I’m hoping someone here can help. The symptoms are these: when I run audacity and try to play audio the interface freezes at about 10 milliseconds into playback and no sound is output. Simultaneously jack starts reporting xruns at a rate of about 20 per second and all sound output is prevented for all programs until I restart. I tried to reproduce the problem on my laptop and a virtual machine (using virtualbox) in both cases, everything works perfectly. The only difference in the filesystem between the three machines is that I’ve been carrying around the same home folder (using deja dup) for the last 4 or 5 reinstalls of linux. Because of this I think that some file in my home folder is causing this conflict. I have tried deleting the ~/.config/jack and ~/.audacity-data folders, and reconfiguring jack. To be clear, jack works fine with chrome and vlc (pulseaudio bridge) and with ardour (bare jack)

All help gratefully appreciated.

Have you selected “Jack Audio System” as the “host” in the Device Toolbar?

I cannot. The host is preset as alsa, and when I click on it, the options are identical to the input device options. New info, I do not need to press play to cause the xruns and lack of sound it turns out.

When Audacity has been built with Jack support, and Jack is running, then the “host” setting give options of “ALSA” or “Jack Audio System” (Jack must be running before launching Audacity).

I don’t know what to tell you, here is a 3:07 video showing what happens. maybe that will help.

I think the problem is with the flatpak packages.
I can’t test it because the flatpak version of Audacity doesn’t run at all on my system (Xubuntu 18.04).

I’ve made a short video to show what should happen (sorry I forgot to record the mouse pointer, but it illustrates that Audacity with Jack does work when installed as a native application).

You will see that the “host” setting has the options “ALSA” or “Jack Audio Connection Kit”. To use ALSA requires that Jack is set up with a bridge between PulseAudio and Jack, but selecting Jack allows Audacity to directly connect to Jack’s “system” input / output (or any other Jack Sinks / Sources).

What I tried (in order):
1.) setting up a new user with jack - no difference
2.) installing the snap version - would not start
3.) installing the official repo version (1:2.4.1-4) this also crashes jack on startup, and the host list is even longer but includes a “jack” option. selecting it crashes audacity.
4.) closing all audio programs and stopping jack then running audacity. This works.

Any further ideas? logs to check? anything?

Try changing the “Project Rate” in Audacity (bottom left corner of the main window) to 48000 (the same as Jack).

Sorry for taking so long.
I changed the sample rate as you said, now it says “error opening sound device. Try changing the audio host, playback device and the project sample rate.”

I also changed the preferences to “jack audio connection kit” for the host and project default sample rate to 48000 and rebooting. It still makes jack start xruns at audacity launch and gives the above error when I try to play anything.

I thought you couldn’t do that :confused:

Why do you need to use Jack rather than plain ALSA (or ALSA+Pulse)?

I am now using the distro repository version, it has a jack audio connection kit option in the preferences and a “jack” (no audio connection kit) option in the host pop down using the popdown crashes audacity.

I have been using jack for everything since installing ardour to save time. I don’t technically need to use it, but quitting and restarting all my apps that use audio to switch contexts is somewhat of a hassle.

I’ve now also tried running audacity in konsole with the command “audacity > audacity.log 2> audacityerr.log” audacity.log is empty, I’ve attached audacityerr.log and in the konsole window, it says “Segmentation fault (core dumped)” after I try to quit.
audacityerr.log (265 KB)

I’m running out of suggestions.
You could perhaps try increasing Jack’s buffer settings.