AVPlayer和AVPlayerItem在使用完毕后需要进行释放，以避免内存泄漏问题。下面是一个示例代码，演示了如何正确释放AVPlayer和AVPlayerItem。

import AVFoundation

class PlayerViewController: UIViewController {

    var player: AVPlayer?
    var playerItem: AVPlayerItem?

    override func viewDidLoad() {
        super.viewDidLoad()

        guard let videoURL = URL(string: "https://example.com/video.mp4") else {
            return
        }

        playerItem = AVPlayerItem(url: videoURL)
        player = AVPlayer(playerItem: playerItem)

        let playerLayer = AVPlayerLayer(player: player)
        playerLayer.frame = view.bounds
        view.layer.addSublayer(playerLayer)

        player?.play()
    }

    override func viewWillDisappear(_ animated: Bool) {
        super.viewWillDisappear(animated)

        player?.pause()
        player = nil

        playerItem?.removeObserver(self, forKeyPath: "status")
        playerItem = nil
    }
}

在上面的示例中，AVPlayer和AVPlayerItem的释放是在视图控制器的viewWillDisappear方法中进行的。首先，调用player?.pause()来暂停播放，并将player设置为nil来释放其内存。然后，调用playerItem?.removeObserver(_:forKeyPath:)方法来移除观察者，最后将playerItem设置为nil来释放其内存。

请注意，上述示例中的URL仅用作演示目的，实际使用时需要替换为有效的视频URL。