[ae/osxsink] - we need to open the stream before determining the channel map - else the layout on the device might be not the final one (happens when transitioning from 2.0 stereo to > 2.0 multichannel formats)
[ae/osxsink] - when opening a stream wait for 100ms on the stream change callback - this ensures that the speaker layout of the device is most likely set properly after opening the desired stream