AURenderCallbackStruct in Swift - swift

Question

I have an Objective-C example to an AURenderCallbackStruct, and I would like to do one in swift. I read it's not possible, is that correct?
Thank you.

Answer 1

You can format a callback function in Swift 4 like the following.
func recordingCallback(
inRefCon:UnsafeMutableRawPointer,
ioActionFlags:UnsafeMutablePointer<AudioUnitRenderActionFlags>,
inTimeStamp:UnsafePointer<AudioTimeStamp>,
inBusNumber:UInt32,
inNumberFrames:UInt32,
ioData:UnsafeMutablePointer<AudioBufferList>?) -> OSStatus {
return noErr
}
Note this must be a global function and not inside of a class.
You can then set your callback function with the following code:
var callbackStruct = AURenderCallbackStruct()
callbackStruct.inputProc = recordingCallback
callbackStruct.inputProcRefCon = nil
status = AudioUnitSetProperty(remoteIOUnit!,
kAudioOutputUnitProperty_SetInputCallback,
kAudioUnitScope_Global,
bus1,
&callbackStruct,
UInt32(MemoryLayout<AURenderCallbackStruct>.size));
if (status != noErr) {
return status // Do something with the error
}
Source

Answer 2

It's possible. Use the following code for your Audio Unit settings.
init() {
var status: OSStatus
do {
try AVAudioSession.sharedInstance().setPreferredIOBufferDuration(preferredIOBufferDuration)
} catch let error as NSError {
print(error)
}
var desc: AudioComponentDescription = AudioComponentDescription()
desc.componentType = kAudioUnitType_Output
desc.componentSubType = kAudioUnitSubType_VoiceProcessingIO
desc.componentFlags = 0
desc.componentFlagsMask = 0
desc.componentManufacturer = kAudioUnitManufacturer_Apple
let inputComponent: AudioComponent = AudioComponentFindNext(nil, &desc)
status = AudioComponentInstanceNew(inputComponent, &audioUnit)
checkStatus(status)
var flag = UInt32(1)
status = AudioUnitSetProperty(audioUnit, kAudioOutputUnitProperty_EnableIO, kAudioUnitScope_Input, kInputBus, &flag, UInt32(sizeof(UInt32)))
checkStatus(status)
status = AudioUnitSetProperty(audioUnit, kAudioOutputUnitProperty_EnableIO, kAudioUnitScope_Output, kOutputBus, &flag, UInt32(sizeof(UInt32)))
checkStatus(status)
var audioFormat: AudioStreamBasicDescription! = AudioStreamBasicDescription()
audioFormat.mSampleRate = 8000
audioFormat.mFormatID = kAudioFormatLinearPCM
audioFormat.mFormatFlags = kAudioFormatFlagIsSignedInteger | kAudioFormatFlagIsPacked
audioFormat.mFramesPerPacket = 1
audioFormat.mChannelsPerFrame = 1
audioFormat.mBitsPerChannel = 16
audioFormat.mBytesPerPacket = 2
audioFormat.mBytesPerFrame = 2
status = AudioUnitSetProperty(audioUnit, kAudioUnitProperty_StreamFormat, kAudioUnitScope_Output, kInputBus, &audioFormat, UInt32(sizeof(UInt32)))
checkStatus(status)
try! AVAudioSession.sharedInstance().setCategory(AVAudioSessionCategoryPlayAndRecord)
status = AudioUnitSetProperty(audioUnit, kAudioUnitProperty_StreamFormat, kAudioUnitScope_Input, kOutputBus, &audioFormat, UInt32(sizeof(UInt32)))
checkStatus(status)
// Set input/recording callback
var inputCallbackStruct = AURenderCallbackStruct(inputProc: recordingCallback, inputProcRefCon: UnsafeMutablePointer(unsafeAddressOf(self)))
AudioUnitSetProperty(audioUnit, AudioUnitPropertyID(kAudioOutputUnitProperty_SetInputCallback), AudioUnitScope(kAudioUnitScope_Global), 1, &inputCallbackStruct, UInt32(sizeof(AURenderCallbackStruct)))
// Set output/renderar/playback callback
var renderCallbackStruct = AURenderCallbackStruct(inputProc: playbackCallback, inputProcRefCon: UnsafeMutablePointer(unsafeAddressOf(self)))
AudioUnitSetProperty(audioUnit, AudioUnitPropertyID(kAudioUnitProperty_SetRenderCallback), AudioUnitScope(kAudioUnitScope_Global), 0, &renderCallbackStruct, UInt32(sizeof(AURenderCallbackStruct)))
flag = 0
status = AudioUnitSetProperty(audioUnit, kAudioUnitProperty_ShouldAllocateBuffer, kAudioUnitScope_Output, kInputBus, &flag, UInt32(sizeof(UInt32)))
}