I have an AU audio effect, that can accept mono/stereo as input, stereo as output, both configured as such in isBusesLayoutSupported as well as in the BusesProperties of the audio processor.
No matter the BusesProperties layout I use, Logic Pro seems to be displaying a “dual mono” mode in the menu to add the plug-in to a track. The isBusesLayoutSupported() is not called until the moment I try to instantiate the plug-in, in which case, it fails as expected because output mono is not supported:
Failed to load Audio Unit “XXX”, please contact the manufacturer for an updated version or further assistance.
This doesn’t happen if isBusesLayoutSupported() accepts mono output (but it eventually crashes as my plug-in is stereo-out and tries to write to the second channel).
Is there a way to prevent this “dual mono” button to appear? I see that some built-ins AU with Logic are able to declare themselves as 100% stereo, without the “dual mono” mode in the menu. My guess is that somehow, the BusesProperties passed in the constructor needs to have this information, but I can’t see it.