Add Observer for end of short, high resolution video - swift

Question

I am trying to play a 4k Video in the AVPlayer with Swift 3 for iOS12 and it works totally fine, but i want this video to play inside a loop. I found articles that stated, that you should use this method to register for the end of the video playback:
NotificationCenter.default.addObserver(self, selector: #selector(self.replay),
name:NSNotification.Name.AVPlayerItemDidPlayToEndTime, object: nil)
In this case self.replay is beeing called once the player reached the end of the video. This works fine for normal videos, but once i try to play a ~4 second long video it does not loop.
The replay function looks like this:
#objc func replay() {
self.playerViewController!.player?.seek(to: CMTime.zero)
self.playerViewController!.player!.playImmediately(atRate: 1)
}
Im adding the Observer in the presenting ViewController's viewDidLoad.
Is this a race-condition, because as stated longer videos work fine? How can i prevent this behaviour.
(Sidenote: Not a regular poster, so please tell me if my question is asked wrong or hard to understand)

Answer 1

NotificationCenter.default.addObserver(self, selector: #selector(replay),
name:NSNotification.Name.AVPlayerItemDidPlayToEndTime, object: nil)
#objc func replay() {
self.playerViewController!.player!.seek(to: CMTime.zero)
self.playerViewController!.player!.play()
}
Not sure what playImmediately(atRate:) does, however, I know in my experience playing videos on loop is to reset the player to time zero, as you have done. Then, just naturally play the video.
ADDITION: On another note, you can WAIT until the video is ready to play to add the observer AND start the video.
override func viewDidLoad() {
player.addObserver(self, forKeyPath: "status", options: [], context: nil)
}
override func observeValue(forKeyPath keyPath: String?, of object: Any?, change: [NSKeyValueChangeKey : Any]?, context: UnsafeMutableRawPointer?) {
if(keyPath == "status" && self.playerViewController!.player!.status == .readyToPlay) {
NotificationCenter.default.addObserver(self, selector: #selector(replay), name:NSNotification.Name.AVPlayerItemDidPlayToEndTime, object: nil)
self.playerViewController!.player!.play()
}
}