A quick example of using AVAudioEngine to process audio from a device's mic then send it to the output.

The processing done in this example is run a forward discreet cosine transform (DCT) on samples of raw mic input, do something with the resulting frequency domain data, then use a reverse DCT to convert it back to time-based audio, and play it through the selected output.

This should run fine on an XCode simulator, or on your device.

Note that it has only been tested on an iPhone 12 Pro, and even on that speedy device we have to drop some raw audio with the example of processing using a forward and reverse discrete cosine transform.

• @shaabans