Can't automate VST3 plugin parameters

This is for a VST3 plugin I am developing myself, so it could be my fault. I’d like to know what reason there might be for Ardour to not allow automation of parameters.

The plugin has 2 parameters, both of which go from -1.0 to +1.0. Both appear in Ardour’s own generic UI when I select ‘Edit with generic controls’. The params can be changed manually in the generic UI, and everything works fine, except that the automation type can’t be selected (they are greyed out). ‘Inline controls’ is also greyed out for this plugin.

When I click the Automation button on the track in the Edit window, ‘Processor automation’ does not appear.

If I build the plugin as VST2, everything’s fine and I can automate the parameters.

Any idea why they might not be automatable for VST3? I have set them as automatable in the framework I’m using (DISTRHO DPF).

Any suggestions appreciated!

After experimenting a bit, I found automation settings return if I remove the plugin’s MIDI input and output ports (and midi processing). Then the parameters are available for automation. But when it has MIDI processing, the automation options aren’t available…

Update: apparently this was due to the way DISTRHO DPF does MIDI in VST3, and x42 is updating to fix it. Thank you!

That seems like it has an assumption that you will either automate parameters or control with MIDI, but not alternate between the two methods in the same project.

For future reference: VST3: Can't automate VST3 parameters in Ardour · Issue #458 · DISTRHO/DPF · GitHub

td;dr: for VST3 MIDI plugins DPF adds a couple of thousand control ports (to expose MIDI CCs) before all other ctrl ports.

Ardour imposes a limit on the number of automatable parameters per plugin (by default to 512). So the control ports of @e_r 's VST3 plugin (which are parameter 3000ish) were marked as “not automatable”.

This limit can be changed or lifted in Preferences > Performance.

The tooltip of that preference reads:

Some Plugins expose an unreasonable amount of control-inputs. This option limits the number of parameters that can are listed as automatable without restricting the number of total controls. This reduces lag in the GUI and shortens excessively long drop-down lists for plugins with a large number of control ports.

should probably be “that are listed”.

Indeed. Thank you!