[solved..] Idiosyncratic combination causes crackles

[Impostor]

If I load Carla as vst plugin in MusE, and then load a vst3 synth (tried: Open303, Osirus, Odin2, Dexed, Monique, Vitalium) in Carla, then turning knobs or sliders in the GUI causes a crackling sound.

This only happens with the specific combination MusE + Carla-VST + Plugin-VST3.

MusE + Carla-LV2 + Plugin-VST3, Renoise + Carla-VST + Plugin-VST3, MusE + Carla-VST + Plugin-VST2, and also Carla Standalone + Plugin-VST3 combinations are fine.

*All plugin formats Linux native.

[Tim E. Real]

Tested on a brand new install of openSUSE Tumbleweed (not by choice - by borking the previous install !).
Quite painful to get set up again...

This is a rolling distro - all packages are up to the minute very latest.

I used Dexed vst3 and Odin2 vst3 downloaded from their sites, hosted in Carla-vst which was hosted in MusE as a vst2.
(I can't believe it's all working, frankly.)

All software is stock distro packaged, except for Dexed and Odin2 and MusE.

Results: No trouble seen or heard.
No trouble was heard when operating Dexed or Odin2 GUI controls, whether playing notes or not.

More info or tests needed?

Wild shot in the dark: Could it be a feedback loop in the midi path, say from Carla through MusE and back to Carla?
Also watch out for system Midi 'through' ports which when used can sometimes accidentally cause Midi feedback.
Avoid using such Midi 'through' ports unless being careful.
Probably not the cause of this issue, though.

[Impostor]

Results: No trouble seen or heard.
No trouble was heard when operating Dexed or Odin2 GUI controls, whether playing notes or not.

Thanks for checking. Guess I'll just have to avoid the VST version of Carla.

Weird thing: with Odin2 there's two ways to assign midi control over a knob: by right-clicking it in the GUI, and by using Carla's "Parameters" menu for the plugin. If I do it via the "Parameters" tab, then using midi control crackles the same way as when using the mouse. But if I assign a cc with midi learn by right-clicking the GUI, then the crackling does not occur with midi control.

[Impostor]

Results: No trouble seen or heard.
No trouble was heard when operating Dexed or Odin2 GUI controls, whether playing notes or not.

Thanks for checking. Guess I'll just have to avoid the VST version of Carla.

Weird thing: with Odin2 there's two ways to assign midi control over a knob: by right-clicking it in the GUI, and by using Carla's "Parameters" menu for the plugin. If I do it via the "Parameters" tab, then using midi control crackles the same way as when using the mouse. But if I assign a cc with midi learn by right-clicking the GUI, then the crackling does not occur with midi control.

Well, I tried the Carla-git VST: no crackling...so I guess this is solved.

[Tim E. Real]

Let's hope it stays that way.

Side note:
Can you guess which new audio server is now installed with this distro (and many others) ?
I spent many hours reading very long threads and posts by many people including you and several other MusEers.
Thank you for the roses! ("MusE is da bomb!" - quote from you.)

I was aware of Pipewire, of course, but now I am forced to deal with it head-on.
Problem out of the gate: Can I please just set MusE's samplerate and buffer size. Please? Config files? Bah!
A recommended command line that was given did not work to change the sample rate or buffer size of Jack and MusE.
I am realizing that with such dynamic on-the-fly changes to samplerate and buffer size,
MusE may have to change to accept dynamic changes like that.
Or we may need to write a native PW driver to take full advantage of features.
Maybe we can finally be able to set samplerate and buffer size from within MusE.
Once I am familiar with PW I may have some thoughts to contribute...

I installed a verrry cool PW app called 'coppwr' that was introduced in one of the posts.
Quite powerful and revealing. Great for seeing what goes on.

Cheers...
T.

[Impostor]

I was aware of Pipewire, of course, but now I am forced to deal with it head-on.

Good luck with that! My LTS distro is due for an upgrade mid 2025, and I hope that at that time Pipewire has matured in all relevant aspects. @rncbc seems (seemed?) not too confident yet in its Jack-transport realization.

And I hope that at that time pipewire works natively without any jack or pulse emulations with all my audio applications. But it will be how it will be.