ios - HLS 直播流视频在首次加载时无法播放

Question

我正在尝试在 iOS 中进行直播，因此遵循以下步骤 -

1. 初始化播放器

   player                 = AVPlayer()
   player.rate            = 1.0
   player.actionAtItemEnd = AVPlayerActionAtItemEnd.none
   

2. 设置播放器层

   playerLayer                 = AVPlayerLayer(player: player)
   playerLayer.frame           = self.bounds
   playerLayer.backgroundColor = UIColor.clear.cgColor
   playerLayer.videoGravity    = AVLayerVideoGravity.resizeAspectFill
   
   if let sublayers = self.layer.sublayers {
   
       for layer in sublayers {
           layer.removeFromSuperlayer()
       }
   }
   
   self.layer.addSublayer(playerLayer)
   

3. 设置播放器项目

   let avAsset = AVURLAsset(url: streamingUrl)
   playerItem = AVPlayerItem(asset: avAsset)
   

4. 替换播放器中的当前Item并播放

   self.player?.replaceCurrentItem(with: self.playerItem)
   self.player?.play()
   

如果我在流式传输开始后加载播放器，我的视频播放效果非常好，但如果我在从后端开始实时流式传输之前加载播放器，然后在一段时间后开始流式传输，则它不会播放视频。

我尝试向playerItem的status属性添加一个观察者，但这在上面提到的条件下也不会改变，只有当我在流媒体开始后加载播放器并且一切正常时才会改变。所以我的问题是为什么我没有收到playerItem 的状态更改？我错过了什么吗？请帮忙。提前致谢。

Answer 1

根据您的情况，使用 AVAsset(url: URL).isPlayable 检查 url 是否可播放，然后才能播放

if avAsset.isPlayable {
    playerItem = AVPlayerItem(asset: avAsset)
    ...
}

为了更好的方法，使用观察者

class ViewController: UIViewController {

    private var observerContext = 0
    private let player = AVPlayer()
    private var readyForPlayback = false

    private var playerItem: AVPlayerItem? {
        willSet {
            playerItem?.removeObserver(self, forKeyPath: #keyPath(AVPlayerItem.status), context: &observerContext)
        }

        didSet {
            playerItem?.addObserver(self, forKeyPath: #keyPath(AVPlayerItem.status), options: [.initial, .new], context: &observerContext)
        }
    }

    private var asset: AVAsset? {
        willSet {
            readyForPlayback = false
            asset?.removeObserver(self, forKeyPath: #keyPath(AVURLAsset.isPlayable), context: &observerContext)
        }

        didSet {
            guard asset == nil else {
                asset!.addObserver(self, forKeyPath: #keyPath(AVURLAsset.isPlayable), options: [.initial, .new], context: &observerContext)
                return
            }

            playerItem = nil
            player.replaceCurrentItem(with: nil)
        }
    }

    // MARK: KVO
    override func observeValue(forKeyPath keyPath: String?, of object: Any?, change: [NSKeyValueChangeKey : Any]?, context: UnsafeMutableRawPointer?) {
        guard context == &observerContext else {
            super.observeValue(forKeyPath: keyPath, of: object, change: change, context: context)
            return
        }

        guard let keyPath = keyPath else { return }

        switch keyPath {
        case #keyPath(AVURLAsset.isPlayable):
            guard asset?.isPlayable == true else { return }
            playerItem = AVPlayerItem(asset: asset!)
            player.replaceCurrentItem(with: playerItem)
        case #keyPath(AVPlayerItem.status):
            guard let status = playerItem?.status else { return }

            if status == .readyToPlay {
                guard !readyForPlayback else { return }
                readyForPlayback = true
                player.play()
            } else if status == .failed {
                readyForPlayback = false
                if let error = playerItem?.error {
                    print("Error: \(error)")
                }
            }
        default:
            super.observeValue(forKeyPath: keyPath, of: object, change: change, context: context)
        }
    }
}

使用

self.asset = AVAsset

停止播放

self.asset = nil