Use Rubberband v4 RubberBandLiveShifter for PitchShiftEffect

[Swiftb0y]

Recently released Rubberband 4.0 contains a new RubberBandLiveShifter that does not support time scaling but only frequency scaling. That is perfect for our PitchShiftEffect. It also has a simpler API that works with fixed size sample input and output counts (similar to our own DSP code). It does this while still minimizing latency. We should consider using it for our PitchShiftEffect instead of the RubberBandStretcher-based solution. It may reduce the realtime latency that the effect currently introduces.

CC @davidchocholaty in case you're interested in a follow up to your GSoC project.

[davidchocholaty]

Thank you for letting me know. Based on your writing, the new Rubber Band improvements sound great. Interested in how it can help reduce the latency. Yeah, definitely. I want to take a look at this. Could you please assign me to it?