AVAudioPlayer produces lag despite prepareToPlay() in Swift

Question

Playing a very short sound (~0.5s) produces a hiccup (like a lag) in my SpriteKit iOS game programmed in Swift. In other questions, I read that I should prepareToPlay(

Answer 1

I ran into this same problem and played the sound in the backgroundQueue.

This is a good example: https://stackoverflow.com/a/25070476/586204.

let qualityOfServiceClass = QOS_CLASS_BACKGROUND
let backgroundQueue = dispatch_get_global_queue(qualityOfServiceClass, 0)
dispatch_async(backgroundQueue, {
    audioPlayer.play()
})

Answer 2

Just adding a Swift 3 version of the solution from @brilliantairic.

DispatchQueue.global().async {
    audioPlayer.play()
}

Answer 3

When I called play multiple times it would cause bad access. I believe the player is being deallocated since this is not thread safe. I created a serial queue to alleviate this problem.

class SoundManager {

    static let shared = SoundManager()

    private init() {
        try? AVAudioSession.sharedInstance().setCategory(AVAudioSessionCategoryPlayback)
        try? AVAudioSession.sharedInstance().setActive(true)
    }

    private let serialQueue = DispatchQueue(label: "SoundQueue", qos: .userInitiated)
    private var player: AVAudioPlayer?

    static func play(_ sound: Sound) {
        shared.play(sound)
    }

    func play(_ sound: Sound) {
        guard let url = Bundle.main.url(forResource: sound.fileName, withExtension: "mp3")
            else { return }

        do {
            try serialQueue.sync {
                self.player = try AVAudioPlayer(contentsOf: url, fileTypeHint: AVFileTypeMPEGLayer3)
                DispatchQueue.main.async {
                    self.player?.play()
                }
            }
        } catch let error as NSError {
            print("error: \(error.localizedDescription)")
        }
    }

}