AvPlayer：视频正在播放声音，而不是设备上的视频

Question

我正在我的应用中播放本地视频。应用程序在模拟器上运行良好，但应用程序未在实际设备上显示视频，仅播放声音并且显示控件的其余部分为黑色。以下是我正在使用的代码：

 @IBAction func play_video(_ sender: Any) {
        
        guard let path = Bundle.main.path(forResource: "app_tutorial", ofType: "mp4") else {
            return
        }
        let videoURL = NSURL(fileURLWithPath: path)

        // Create an AVPlayer, passing it the local video url path
        let player = AVPlayer(url: videoURL as URL)
        let controller = AVPlayerViewController()
        let audioSession = AVAudioSession.sharedInstance()

        do
        {
           try audioSession.setCategory(AVAudioSessionCategoryPlayback, with: .duckOthers)
        }
        catch
        {
           print("AVAudioSession cannot be set")
        }
        
        controller.player = player
        present(controller, animated: true) {
//            player.play()
            DispatchQueue.main.async {
                player.play()
            }
        }
    }

如果缺少什么，请指导我。 预先感谢