AVPlayerViewController显示黑屏

Question

我正在尝试使用以下代码在AVplayer中播放视频，但它显示黑屏。我也尝试了谷歌搜索，但没有任何运气

let url = URL(string: "https://clips.vorwaerts-gmbh.de/big_buck_bunny.mp4")

let asset = AVURLAsset(url: url!)
let item = AVPlayerItem(asset: asset)

let player = AVPlayer.init(playerItem: item)
let playerController = AVPlayerViewController()

 playerController.player = player
 self.addChildViewController(playerController)
 self.view.addSubview(playerController.view)
 playerController.view.frame = self.view.frame
 player.play()

我还为TransportSecurity添加了plist条目。