This is simple demo app to show how to reverse a clip of audio file with AVFoundation, specifically, the AVFAudio part.
In this demo, I just use AVAudioFile/AVAudioPCMBuffer/AVAudioFormat to reverse a m4a audio file, besides, it illustrates how to use the UnSafe part of Swift :)
Due to the implementation, which just read all the samples from origin audio file to memory PCM buffer, it' not an optimized solution to do so and probably would cause memory problem. In practice you should process segment by segment.
For this demo, I use a m4a file with bit rate of about 64 kb/s and duration of 62 seconds and the peak of memory use is about 13 MB for the PCM buffer memory.
I can't give a comment as I ain't got that much reputation to do so.