An interface to a set of audio processing unit callback functions.

this serves as the method of communication between the client and the audio processing unit.

The class is a mixin and is intended to be inherited by the client class that is interested in observing the audio processing unit operation. The functions encapsulated by this class are called when specific events occur while processing audio.

this interface is mainly usable for advanced audio clients, that are interested in detailed operation of the processing chain. Most audio clients should be fine with only observing the audio stream.