iOS: Recording audio from the mic & saving it to a file

ios_record_audio_to_file.swift

// Recording audio to a file:
var engine = AVAudioEngine()
var distortion = AVAudioUnitDistortion()
var reverb = AVAudioUnitReverb()
var audioBuffer = AVAudioPCMBuffer()
var outputFile = AVAudioFile()
var delay = AVAudioUnitDelay()

func initializeAudioEngine() {
    engine.stop()
    engine.reset()
    engine = AVAudioEngine()

    isRealTime = true
    do {
        try AVAudioSession.sharedInstance().setCategory(AVAudioSessionCategoryPlayAndRecord)

        let ioBufferDuration = 128.0 / 44100.0

        try AVAudioSession.sharedInstance().setPreferredIOBufferDuration(ioBufferDuration)

    } catch {

        assertionFailure("AVAudioSession setup error: \(error)")
    }

    let fileUrl = URLFor("/NewRecording.caf")
    print(fileUrl)
    do {

        try outputFile = AVAudioFile(forWriting:  fileUrl!, settings: engine.mainMixerNode.outputFormatForBus(0).settings)
    }
    catch {

    }

    let input = engine.inputNode!
    let format = input.inputFormatForBus(0)

    //settings for reverb
    reverb.loadFactoryPreset(.MediumChamber)
    reverb.wetDryMix = 40 //0-100 range
    engine.attachNode(reverb)

    delay.delayTime = 0.2 // 0-2 range
    engine.attachNode(delay)

    //settings for distortion
    distortion.loadFactoryPreset(.DrumsBitBrush)
    distortion.wetDryMix = 20 //0-100 range
    engine.attachNode(distortion)


    engine.connect(input, to: reverb, format: format)
    engine.connect(reverb, to: distortion, format: format)
    engine.connect(distortion, to: delay, format: format)
    engine.connect(delay, to: engine.mainMixerNode, format: format)

    assert(engine.inputNode != nil)

    isReverbOn = false

    try! engine.start()
}

func startRecording() {

    let mixer = engine.mainMixerNode
    let format = mixer.outputFormatForBus(0)

    mixer.installTapOnBus(0, bufferSize: 1024, format: format, block:
        { (buffer: AVAudioPCMBuffer!, time: AVAudioTime!) -> Void in

            print(NSString(string: "writing"))
            do {
                try self.outputFile.writeFromBuffer(buffer)
            }
            catch {
                print(NSString(string: "Write failed"));
            }
    })
}

func stopRecording() {

    engine.mainMixerNode.removeTapOnBus(0)
    engine.stop()
}