Open Radar

 
Area:
AVFoundation

Summary:
When stopping an AVAudioPlayer close to the end and then playing it again, it will enter into an infinite loop but without any audio being heard. The audio will not come back even after repeated play()/pause() attempts unless the player is de-inited and recreated.

Steps to Reproduce:
This can be reproduced by playing back audio, and then tapping pause just before the end. If done at the right moment, the playback will enter into an infinite loop without anything being heard.

This code will reproduce it:

import UIKit
import AVFoundation

class ViewController: UIViewController, AVAudioPlayerDelegate {
    var player: AVAudioPlayer?
    var intercept: Bool = true
    
    @IBOutlet weak var progressView: UIProgressView!
    
    @IBOutlet weak var playButton: UIButton!
    
    override func viewDidLoad() {
        super.viewDidLoad()
        let displayLink = CADisplayLink.init(target: self, selector: #selector(pollCurrentTime))
        displayLink.add(to: RunLoop.main, forMode: RunLoopMode.defaultRunLoopMode)
    }

    override func didReceiveMemoryWarning() {
        super.didReceiveMemoryWarning()
        // Dispose of any resources that can be recreated.
    }

    @IBAction func onPlayButtonTapped(_ sender: UIButton) {
        let asset = NSDataAsset(name:"TestRecording")!
        player = try! AVAudioPlayer(data: asset.data, fileTypeHint: "m4a")
        player!.delegate = self
        player!.play()
        playButton.isEnabled = false
    }
    
    func pollCurrentTime() {
        if let player = player {
            progressView.progress = Float(player.currentTime / player.duration)
            if intercept && progressView.progress > 0.97 {
                intercept = false
                player.pause()
                DispatchQueue.main.asyncAfter(deadline: .now() + 0.25) {
                    player.play()
                }
            }
        } else {
            progressView.progress = 0
        }
    }
    
    func audioPlayerDidFinishPlaying(_ player: AVAudioPlayer, successfully flag: Bool) {
        cleanup()
    }
    
    func audioPlayerDecodeErrorDidOccur(_ player: AVAudioPlayer, error: Error?) {
        cleanup()
    }
    
    private func cleanup() {
        self.player = nil
        playButton.isEnabled = true
        intercept = true
    }
}

Expected Results:
This should not happen.

Observed Results:
Happens on iPhone 6, iOS 10.3.2

Version:
10.3.2 (14F89)

Notes:
Additional notes: Seems that currentTime goes to 0 even though we paused close to the end, but neither of the two delegate methods were called.

Configuration:
iPhone 6s