基于蜂窝数据的 AVFoundation答案

【问题标题】：AVFoundation over Cellular Data基于蜂窝数据的 AVFoundation
【发布时间】：2021-08-17 02:46:12
【问题描述】：

当我使用下面的代码并通过 Wifi 从 Firebase 拉取我的 https 视频链接时，一切都很顺利，视频立即播放，问题为零。当我在蜂窝网络上使用相同的代码时，一切都变得非常缓慢，就像视频暂停并且永远加载一样。

如果它是从文件播放的，无论我使用的是蜂窝网络还是 Wifi 都没有关系。这里有什么问题？

数据模型：

class Video {

    var httpsStr: String?
    var videoURL: URL?        

    convenience init(dict: [String: Any] {
        self.init()

        if let httpsStr = dict["httpsStr"] as? String {

            self.httpsStr = httpsStr

            let url = URL(string: httpsStr)!
            let assetKeys = [ "playable", "duration"]

            let asset = AVURLAsset(url: url)
            asset.loadValuesAsynchronously(forKeys: assetKeys, completionHandler: {
                DispatchQueue.main.async {
                
                    self.videoURL = asset.url

                    // save videoURL to FileManager to play video from disk
                }
            })
        }
    } 
}

Firebase 拉取：

ref.observeSingleEvent(of: .value) { (snapshot) in

    guard let dict = snapshot.value as? [String: Any] else { return }

    let video = Video(dict: dict)
    self.video = video

    DispatchQueue.main.asyncAfter(deadline: .now() + 2, execute: {
        self.playVideo()
    }
}

播放视频：

func playVideo() {

    // init AVPlayer ...

    guard let videoURL = self.video.videoURL else { return }

    let lastPathComponent = videoURL.lastPathComponent
    let file = FileManager...appendingPathComponent(lastPathComponent)

    if FileManager.default.fileExists(atPath: file.path) {

        let asset = AVAsset(url: file)
        play(asset)

    } else {

        let asset = AVAsset(url: videoURL)
        play(asset)
    }
}

func play(_ asset: AVAsset) {
    
    self.playerItem = AVPlayerItem(asset: asset)

    self.player?.automaticallyWaitsToMinimizeStalling = false // I also set this to true
    self.playerItem?.preferredForwardBufferDuration = TimeInterval(1)

    self.player?.replaceCurrentItem(with: playerItem!)
    // play video
}

【问题讨论】：

标签： ios swift firebase-realtime-database avfoundation

【解决方案1】：

我关注了这个answer，现在在蜂窝数据上一切似乎都很顺利。我需要在assetKeys 中包含tracks 属性。

您使用 AVURLAsset 从 URL 创建资产。创建资产，但是，并不一定意味着它已经可以使用了。成为使用时，资产必须已加载其轨道。

class Video {

    var httpsStr: String?
    var videoURL: URL?        

    convenience init(dict: [String: Any] {
        self.init()

        if let httpsStr = dict["httpsStr"] as? String {

            self.httpsStr = httpsStr

            let url = URL(string: httpsStr)!
            let assetKeys = ["playable", "duration", "tracks"] // <----- "tracks" added here

            let asset = AVURLAsset(url: url)
            asset.loadValuesAsynchronously(forKeys: assetKeys, completionHandler: {

                var error: NSError? = nil
                let status = asset.statusOfValue(forKey: "tracks", error: &error)
                switch status {

                    case .loaded:
                        // Sucessfully loaded, continue processing
                        DispatchQueue.main.async {
                
                            self.videoURL = asset.url
                            // save videoURL to FileManager to play video from disk
                        }

                    case .failed: 
                        // Examine NSError pointer to determine failure
                        print("Error", error?.localizedDescription as Any)

                    default: 
                        // Handle all other cases
                        print("default")
                }
            })
        }
    } 
}

【讨论】：