How to use an Audio Unit on the iPhone

Question

I\'m looking for a way to change the pitch of recorded audio as it is saved to disk, or played back (in real time). I understand Audio Units can be used for this. The iPhone off

Answer 1

I've used the NewTimePitch audio unit for this before, the Audio Component Description for that is

var newTimePitchDesc = AudioComponentDescription(componentType: kAudioUnitType_FormatConverter,
        componentSubType: kAudioUnitSubType_NewTimePitch,
        componentManufacturer: kAudioUnitManufacturer_Apple,
        componentFlags: 0,
        componentFlagsMask: 0)

then you can change the pitch parameter with an AudioUnitSetParamater call. For example this changes the pitch by -1000 cents

err = AudioUnitSetParameter(newTimePitchAudioUnit,
        kNewTimePitchParam_Pitch,
        kAudioUnitScope_Global,
        0,
        -1000,
        0)

The parameters for this audio unit are as follows

    // Parameters for AUNewTimePitch
enum {
      // Global, rate, 1/32 -> 32.0, 1.0
  kNewTimePitchParam_Rate                         = 0,
      // Global, Cents, -2400 -> 2400, 1.0
  kNewTimePitchParam_Pitch                        = 1,
      // Global, generic, 3.0 -> 32.0, 8.0
  kNewTimePitchParam_Overlap                      = 4,
      // Global, Boolean, 0->1, 1
  kNewTimePitchParam_EnablePeakLocking            = 6
};

but you'll only need to change the pitch parameter for your purposes. For a guide on how to implement this refer to Justin's answer