VST does not receive update in channel count with Reaper

Hi everyone,

i was just testing my plugin with Reaper and the there available formats AU, VST and VST3. When I load the plugin as VST3 or AU, it receives an update on the new channel count after changing the channel count of the track it is loaded into. Not so with VST. Anyone knows if it is Reapers fault or something in the Juce code?

Btw. with the Juce Pluginhost it seems to work with VST…



It’s an option per plugin in Reaper you have to enable, from the + button in the plugin window.


Hey Xenakios,

thanks for the hint. Any idea why it is off by default?



The plugin channel IO count stuff is pretty messy on VST2, so this is how they have chosen to deal with it.

in 5.79 they added the canDo wantsChannelCountNotifications - so you can make it default


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And here is how to activate that cando in your Plugins:

Btw Justin frankel changed the behavior to always on for new plugins in reaper afaik.

Channel count stuff works like a charm without any problems yet with the IEM plugins (VST2). Using it for selectable Ambisonic order up to 7th.

Hey everyone, thanks for those hints. Thats what I was looking for.

Some more information:
In <REAPER config directory>/reaper-fxoptions.ini you can see the settings (more or less cryptic) of your current plug-ins. If you are planning on using the canDo, you should delete your plug-ins out of that list, otherwise it won’t react to the changes (ignore the canDo as a matter of fact). Oh and don’t forget to upgrade to the lates Reaper version (well, at least 5.79 as Oli stated)