I think I have spotted the problem:
the method setPlayConfigDetails of AudioProcessor is called only upon creation of the AudioFilterStreamer object, passing the max number of input and output channels as #defined in the plugin characteristics.
What seems to be missing are subsequent calls to setPlayConfigDetails when the audio properties (in particular, when the number of channel) changes.
I mean: every time I change channels in the audio options window, the setAudioDeviceSetup method of AudioDeviceManager is called, but no following calls to AudioProcessor::setPlayConfigDetails happen, while it seems to me like a reasonable behaviour, what do you think?
I got a bit confused by the class hierarchy used for the standalone plugin, so I didn’t dare to implement a solution myself, but I think that a good idea would be to exploit the fact that the AudioDeviceManager can have changeListeners notified when the setup changes… or is it better to make it a synchronous change?
Hope I have been clear enough…