Apple supplied sample code AudioUnitV3Example quite messy as it contains C++, C, Obj-C++, Swift code at once. I faced weird issues while translating sample code to pure Swift. Such as missed mData pointers in buffer lists, In-Place processing behaviour and absence of Software for testing. At least for now (2016 Oct) AULab does not support AUv3. AudioUnitV3Example also does not explain how to build PlugIn which is not pure DSP unit, but for instance Visualiser (Level meter, Oscilloscope, etc.).