Translate Objective - C Introduction to AudioUnits into Swift - ios

Question

I alredy managed to translate this code so the render callback gets called:
http://www.cocoawithlove.com/2010/10/ios-tone-generator-introduction-to.html
I'm sure that my render callback method is not right implemented, because I either get no sound at all or I get pretty awful noise from my headphones.
I also don't see a connection between my audioSession in viewDidLoad and the rest of the code.
Is there anyone who can help me out with this?
private func performRender(
inRefCon: UnsafeMutablePointer<Void>,
ioActionFlags: UnsafeMutablePointer<AudioUnitRenderActionFlags>,
inTimeStamp: UnsafePointer<AudioTimeStamp>,
inBufNumber: UInt32,
inNumberFrames: UInt32,
ioData: UnsafeMutablePointer<AudioBufferList>) -> OSStatus
{
// get object
let vc = unsafeBitCast(inRefCon, ViewController.self)
print("callback")
let thetaIncrement = 2.0 * M_PI * vc.kFrequency / vc.kSampleRate
var theta = vc.theta
// var sinValues = [Int32]()
let amplitude : Double = 0.25
let abl = UnsafeMutableAudioBufferListPointer(ioData)
for buffer in abl
{
let val : Int32 = Int32((sin(theta) * amplitude))
// sinValues.append(val)
theta += thetaIncrement
memset(buffer.mData, val, Int(buffer.mDataByteSize))
}
vc.theta = theta
return noErr
}
class ViewController: UIViewController
{
let kSampleRate : Float64 = 44100
let kFrequency : Double = 440
var theta : Double = 0
private var toneUnit = AudioUnit()
private let kInputBus = AudioUnitElement(1)
private let kOutputBus = AudioUnitElement(0)
#IBAction func tooglePlay(sender: UIButton)
{
if(toneUnit != nil)
{
AudioOutputUnitStop(toneUnit)
AudioUnitInitialize(toneUnit)
AudioComponentInstanceDispose(toneUnit)
toneUnit = nil
}
else
{
createToneUnit()
var err = AudioUnitInitialize(toneUnit)
assert(err == noErr, "error initializing audiounit!")
err = AudioOutputUnitStart(toneUnit)
assert(err == noErr, "error starting audiooutput unit!")
}
}
func createToneUnit()
{
var defaultOutputDescription = AudioComponentDescription(
componentType: kAudioUnitType_Output,
componentSubType: kAudioUnitSubType_RemoteIO,
componentManufacturer: kAudioUnitManufacturer_Apple,
componentFlags: 0,
componentFlagsMask: 0)
let defaultOutput = AudioComponentFindNext(nil,&defaultOutputDescription)
let fourBytesPerFloat : UInt32 = 4
let eightBitsPerByte : UInt32 = 8
var err = AudioComponentInstanceNew(defaultOutput, &toneUnit)
assert(err == noErr, "error setting audio component instance!")
var input = AURenderCallbackStruct(inputProc: performRender, inputProcRefCon: UnsafeMutablePointer(unsafeAddressOf(self)))
err = AudioUnitSetProperty(toneUnit, kAudioUnitProperty_SetRenderCallback, kAudioUnitScope_Global, kOutputBus, &input, UInt32(sizeof(AURenderCallbackStruct)))
assert(err == noErr, "error setting render callback!")
var streamFormat = AudioStreamBasicDescription(
mSampleRate: kSampleRate,
mFormatID: kAudioFormatLinearPCM,
mFormatFlags: kAudioFormatFlagsNativeFloatPacked,
mBytesPerPacket: fourBytesPerFloat,
mFramesPerPacket: 1,
mBytesPerFrame: fourBytesPerFloat,
mChannelsPerFrame: 1,
mBitsPerChannel: fourBytesPerFloat*eightBitsPerByte,
mReserved: 0)
err = AudioUnitSetProperty(toneUnit, kAudioUnitProperty_StreamFormat, kAudioUnitScope_Output, kInputBus, &streamFormat, UInt32(sizeof(AudioStreamBasicDescription)))
assert(err == noErr, "error setting audiounit property!")
}
override func viewDidLoad()
{
super.viewDidLoad()
let audioSession = AVAudioSession.sharedInstance()
do
{
try audioSession.setCategory(AVAudioSessionCategoryPlayback)
}
catch
{
print("Audio session setCategory failed")
}
do
{
try audioSession.setPreferredSampleRate(kSampleRate)
}
catch
{
print("Audio session samplerate error")
}
do
{
try audioSession.setPreferredIOBufferDuration(0.005)
}
catch
{
print("Audio session bufferduration error")
}
do
{
try audioSession.setActive(true)
}
catch
{
print("Audio session activate failure")
}
}

Answer 1

vc.theta isn't being incremented
memset only takes a byte's worth of val
the AudioUnit expects floats, but you're storing Int32s
the range of the audio data looks funny too - why not keep it in the range [-1, 1]?
there's no need to constrain theta either, sin can do that fine.
Are you sure this used to work in objective-c?