Set the buffer size for AVFoundation captures including, e.g, AVCaptureSession via an AVCaptureAudioDataOutput

AVFoundationBufferSize.swift

// couple of useful functions for dealing with an AVCaptureSession
// chucked out there for posterity and search

// What led to me to do this      : Set size of AVCaptureAudioDataOutput buffer
// What might also lead you here  : Swift AudioValueTranslation


// PLEASE NOTE : There are no error checks in this code, demo purposes only.

import AVFoundation

struct Device { // I am great at names!
  
  // original code from a gist : https://gist.github.com/pdesantis/b1899706ea14045eb345de5584d2a3bf
  // updated to remove the warnings and make the behaviour defined.
  
  
  // get the AudioDeviceID from te uniqueID string
  
  static func id(of uniqueID: String) -> AudioDeviceID {
    
    // simples ...
    var uuid     = uniqueID as CFString
    var deviceID = kAudioDeviceUnknown
    
    // still so so ..
    var address = AudioObjectPropertyAddress (
      mSelector: kAudioHardwarePropertyDeviceForUID,
      mScope   : kAudioObjectPropertyScopeGlobal,
      mElement : kAudioObjectPropertyElementMaster
    )
    let insize   = UInt32(MemoryLayout<CFString>.stride)
    let outsize  = UInt32(MemoryLayout<AudioObjectID>.stride)
    var transize = UInt32(MemoryLayout<AudioValueTranslation>.stride)
    
    // real shit ...
    withUnsafeMutablePointer(to: &uuid) { uid in
      withUnsafeMutablePointer(to: &deviceID) { dev in
        var translation = AudioValueTranslation (
          mInputData     : uid,
          mInputDataSize : insize,
          mOutputData    : dev,
          mOutputDataSize: outsize
        )
        AudioObjectGetPropertyData (UInt32(kAudioObjectSystemObject), &address, 0, nil, &transize, &translation)
      }
    }
    // wait, but why?
    // well, long story : https://developer.apple.com/forums/thread/674633
    // short            : swift does not guarantee the life cycle of the pointers you create with &
    //                    this is fine for a scalar but pointers to pointers in a struct? Undefined.
    
    return deviceID // dont forget to check that.
  }
  
  
  
  // set the capture sample buffer size for AVCaptureAudioDataOutput in an AVCaptureSession
  // or just generally for any core audio device you have the ID of
  
  static func setBufferSize(to size: UInt32, for device: UInt32) {
    
    var size = size
    
    var address = AudioObjectPropertyAddress (
        mSelector: kAudioDevicePropertyBufferFrameSize,
        mScope   : kAudioDevicePropertyScopeInput,
        mElement : kAudioObjectPropertyElementMaster
    )
    AudioObjectSetPropertyData(device, &address, 0, nil, UInt32(MemoryLayout<UInt32>.stride), &size)
  }
}