如何在 swift 中使用 AudioKit 生成重复声音

Question

I'm trying to make metronome app that plays sound on repeat (BPM) and with/without each tack volume. I tried to achieve that with Timer and GCD Timer like that:

let interval = TimeInterval(Double(60) / Double(bpm))
timer = Timer.scheduledTimer(timeInterval: interval,
                             target: self,
                             selector: #selector(playTackt),
                             userInfo: nil,
                             repeats: true
@objc func playTackt(){
    if shouldPlaySoundTackts{
        audioPlayer.volume = 1
        playedSoundTackts += 1
        if playedSoundTackts == soundTackts{
            shouldPlaySoundTackts = false
            playedSoundTackts = 0
        }
    }else{
        audioPlayer.volume = 0
        playedMuteTackts += 1
        if playedMuteTackts == muteTackts{
            shouldPlaySoundTackts = true
            playedMuteTackts = 0
        }
    }
  audioPlayer.play()
}

But the problem is that Timer has some lags in miliseconds. Then i tried to replay sound with audioPlayerDidFinishPlaying method but it call's after ~0.5 seconds after sound finish's playing. So is there another way to generate or repeat sound with bpm and with/without each tack volume?

Answer 1

You could try using either the Sequencer or AppleSequencer and assigning the notes as Midi. One known drawback with AppleSampler is a delay in the first note playing. You can see an example of AppleSequencer in MusicToy and Sequencer in the Shaker example of AudioKit/Cookbook on Github.