MPMusicPlayerController.applicationQueuePlayer bugs in iOS 13.4

Question

I submitted Feedback about this in Feedback Assistant already, but figured I'd post here too -- as of iOS 13.4, I have noticed various bugs in the MediaPlayer framework, specifically with the applicationQueuePlayer and applicationMusicPlayer.

The first is that on app launch when it initializes, it now throws this error:

[SDKPlayback] applicationQueuePlayer _establishConnectionIfNeeded timeout [ping did not pong]

That error is followed by this one, when prepareToPlay() is called:

Error Domain=MPMusicPlayerControllerErrorDomain Code=6 "Failed to prepare to play" UserInfo={NSDebugDescription=Failed to prepare to play}

Eventually after calling prepareToPlay enough times it'll get its head on straight and start playing the content, but even then I'm finding I have to call play() or pause() several times for it to do so reliably.

Anyone else seeing this in their apps post-13.4?

Answer 1

For a number of days now, I've been scratching my head as to why I wasn't able to play store identifiers for Apple Music catalog or library content. Turns out, setting the store identifiers directly with MPMusicPlayerApplicationController will play the content, whereas using MPMusicPlayerStoreQueueDescriptor and passing it to MPMusicPlayerApplicationController results in no effect.

I still get the following error logs:

[SDKPlayback] applicationQueuePlayer _establishConnectionIfNeeded timeout [ping did not pong]

[core] "Error returned from daemon: Error Domain=com.apple.accounts Code=9 "(null)""

iTunesCloud] ACAccountStore 0x283e1bdb0 - Error retrieving iTunesStore accounts. err=Error Domain=com.apple.accounts Code=9 "(null)"

[iTunesCloud] [ICUserIdentityStore] Failed to fetch local store account with error: Error Domain=com.apple.accounts Code=9 "(null)".

...but gone is Error Domain=MPMusicPlayerControllerErrorDomain Code=6 "Failed to prepare to play" UserInfo={NSDebugDescription=Failed to prepare to play}.

Hopefully this might be useful for someone else who stumbles into this :)

Here's some code so you see what I mean:

class AMPlayer {

    private(set) var player: MPMusicPlayerController!
    // Every time `queue` is set, it'll ensure the player queue is "updated"
    private var queue: MPMusicPlayerStoreQueueDescriptor! {
        didSet {
            guard self.queue != nil,
                  let storeIDs = self.queue.storeIDs,
                  !storeIDs.isEmpty
            else { return }

            self.player.setQueue(with: storeIDs)
        }
    }
    
    // This is how I set the queue from outside the class
    public func setQueue(with resourceIDs: [String]) {
        self.queue = MPMusicPlayerStoreQueueDescriptor(storeIDs: resourceIDs)
    }

    // This is how I start playback
    public func play() {
        self.player.prepareToPlay { (error) in
            if let error = error as? MPError {
                print("Error while preparing to play: \(error)")
            } else {
                self.player.play()
            }
        }
    }

}

Answer 2

In my situation my player logic didn't always fire the player?.prepareToPlay() code. I make sure to stop() the player, then fire the prepareToPlay immediately after. Then I prep the player with the contentsOf: URL, and adjust the player settings, and then play. I also have some weird volume adjustments I had to add because of a popping sound that was happening. I'll post my player code below.

  static func play(sound: Sound) {
    
 
    stop()
    player?.prepareToPlay()

     let path = Bundle.main.path(forResource: sound.file, ofType: sound.extn)
        let url = URL(fileURLWithPath: path!)
    
    do {
        
        player = try AVAudioPlayer(contentsOf: url)
        player?.volume = 0 //starting volume at zero before playing eliminates pop on start
        player?.numberOfLoops = -1
        player?.play()
        player?.setVolume(1, fadeDuration: 0.3)  //fade in, no pop

    } catch {
      print(error)
    }
}