AEAudioUnitModuleProcess doubles the gain of mono buffers

[jackpal]

I was using mono buffers to debug an AEAudioUnitModule, and I noticed that my output buffers had double the amplitude of my input buffers. (e.g. if my input samples were 1.0 peak-to-peak the output samples are 2.0 peak-to-peak.)

I think this is because AEAudioUnitModuleProcess is hard-coded to create a stereo buffer in line 141 "// Get a buffer with 2 channels". This stereo buffer is initialized with two copies of the original data, and later on output stereo buffers are combined back into a single mono buffer. As a result the amplitude of the samples gets doubled.