Waveform jitter

[crshrprt]

In case it will be helpful for tracking down the problem with the waveform jitter here's a list of DAWs/host I tried on Linux when testing fixing-sync-other-daws branch.

I encountered jitter in:
Ardour 8.2
Carla 2.5.8
Bespoke Synth Nightly 611103f (initially it seemed not affected, but after a while it was noticeable)

[ardura]

Note to whoever works this (or myself for later) - this is probably related to different buffers used in different DAWs altering the timing so it might be easier to change the plugin to go sample-by-sample in processing rather than buffer by buffer. Either that or it is an issue in the nih-plug context.transport() stuff for calculating beat position based off the information the DAW gives the plugin.

[ardura]

Still trying to figure this out. @crshrprt do you use any preroll setting in Ardour?

[crshrprt]

No preroll, it happens also in hosts without that feature.

[ardura]

There's something weird with Ardour on Windows where the Beat displayed isn't the tracked beat from the timeline. I'm thinking this is either miscalculation from rounding errors or some sort of lag between the audio thread and the GUI thread. Even then there is still some jitter with the different solutions I've tried. So I have tried to minimize it where I can. I think we should leave this issue open, but I've updated the project with my changes so far.

[ardura]

1cfbd8f has the latest changes lessening some of the jitter but it's still there unfortunately.

[ardura]

Can you try the latest release build and see if the jitter got better for you?

[crshrprt]

In latest version jitter is better, waveform's start still moves in Ardour but it seems a bit more predictable:

Scrolloscope_Ardour.mp4

In BespokeSynth waveform's start is more stable. In both DAWs the bar synced view is "broken", only a a few ms buffer is displayed:

Scrolloscope_BespokeSynth.mp4

[ardura]

Dang I was hoping that would have fixed it. I'll try and revisit this again soon. I thought of another alternative as well:
I'm wondering if I can try to track it manually too. Based off the sample rate and BPM reported to the plugin, I can start counting samples when the DAW reports it is playing vs stopped in its timeline, then calculate the amount of samples each beat or bar should be to redraw. I'll play with that iea if it's feasible too.

[ardura]

Hey @crshrprt do you use a specific timeline sync in Ardour + your other hosts? I saw in the Ardour manual that MTC timeline control limits the frame rate and that could be part of the issue.

Do you use any external midi timing control or JACK?

[crshrprt]

In my tests in Ardour and BespokeSynth I used the internal transport, no external clock.
The same jitter in Ardour is noticeable also when using JACK as external transport master, there isn't much difference.

[ardura]

Okay I think I got it fixed now, can you try with the latest release? I tested in Ardour and was able to get nicer beat sync happening :)

[crshrprt]

Definitively is better now, and bar mode works too. :)

Scrolloscope_Ardour2.mp4

[ardura]

Great news, I'll mark this as closed then. Thanks for the help testing and validating!