离线 Fairplay AVAssetDownloadTask 在下载时收到未知错误回调（只发生在 iOS 10.2）

Question

我们正在为我们的客户端应用构建离线公平竞赛内容；我们通过参考 HLSCatalog 演示应用程序中的 Apple 示例下载管理器 AssetPersistenceManager class 来实现该功能。我想在这里强调的是 AssetPersistenceManager class 中的一个函数和两个回调，它是

    /
    func downloadStream(for asset: Asset) {
        /
         For the initial download, we ask the URLSession for an AVAssetDownloadTask
         with a minimum bitrate corresponding with one of the lower bitrate variants
         in the asset.
         */
        guard let task = assetDownloadURLSession.makeAssetDownloadTask(asset: asset.urlAsset, assetTitle: asset.name, assetArtworkData: nil, options: [AVAssetDownloadTaskMinimumRequiredMediaBitrateKey: 265000]) else { return }

        /
        task.taskDescription = asset.name

        activeDownloadsMap[task] = asset

        task.resume()

        var userInfo = [String: Any]()
        userInfo[Asset.Keys.name] = asset.name
        userInfo[Asset.Keys.downloadState] = Asset.DownloadState.downloading.rawValue

        NotificationCenter.default.post(name: AssetDownloadStateChangedNotification, object: nil, userInfo:  userInfo)
    }

并在完成下载流时回调

func urlSession(_ session: URLSession, assetDownloadTask: AVAssetDownloadTask, didFinishDownloadingTo location: URL) {
    let userDefaults = UserDefaults.standard

    /
     This delegate callback should only be used to save the location URL
     somewhere in your application. Any additional work should be done in
     `URLSessionTaskDelegate.urlSession(_:task:didCompleteWithError:)`.
     */
    if let asset = activeDownloadsMap[assetDownloadTask] {

        userDefaults.set(location.relativePath, forKey: asset.name)
    }
}

最后一个是didCompleteWithError回调

func urlSession(_ session: URLSession, task: URLSessionTask,
didCompleteWithError error: Error?)

在 iOS < 10.2 上似乎一切正常，但在某些运行最新 iOS 10.2 的设备上进行测试后，应用程序总是收到 didFinishDownloadTo 委托的回调，而只有 13-完成百分比的 15%，之后 didCompleteWithError 错误被调用，我们收到以下错误

> "=======> completed percent 11.2888760669556" .
> "=======> completed percent 11.44566601233" 
> "=======> completed percent 11.7592459030787"
> "=======> completed percent 12.0728257938275" 
> "=======> completed percent 12.5431956299506" 
> "=======> completed percent 13.0135654660738" 
> "=======> completed percent 13.3271453568226" 
> "=======> completed percent 13.6407252475713" 
> "=======> completed percent 13.9543051383201" 
> "=======> completed percent 14.1110950836945" 
> "=======> completed percent 14.2678850290689" 
> "Error Domain=AVFoundationErrorDomain Code=-11800 \"The operation could not
> be completed\" UserInfo={NSLocalizedDescription=The operation could
> not be completed, NSLocalizedFailureReason=An unknown error occurred
> (-12667)}"

检查代理调试应用程序，它指出应用程序在整个接收响应之前关闭连接。

Status
Complete
Failure
Client closed connection before receiving entire response
Response Code
206 Partial Content

只有 iOS 10.2 有这个错误，在低于该版本的其他 OS 上测试的相同流仍然工作正常。试图找到一些关于 iOS 10.2 的更新日志，但我什么也没找到？大家有什么建议吗？

Answer 1

经过一周的坚持，我们自己找到了答案。原来是 iOS 10.0 - 10.1 而不是 10.2 上的错误。错误发生在 30 秒后与 DRM 错误有关，它发生在 iOS 10.2，在 AVAssetDownloadTask 恢复后有来自 AVAssetResourceLoaderDelegate 的回调，您需要点击服务器密钥来完成 [=11= 中的 Fairplay DRM 内容密钥]

func resourceLoader(_ resourceLoader: AVAssetResourceLoader, 
shouldWaitForLoadingOfRequestedResource loadingRequest: AVAssetResourceLoadingRequest) -> Bool

否则，下载将被强制停止，您将收到上述未知错误。 Apple 示例代码 HLSCatalog 只是 non-DRM 流的演示，他们甚至没有提到演示中所需的内容密钥实现。

我们遵循了他们的样本，似乎 iOS 10.0 - 10.1，AVFoundation 在处理下载时没有检查内容密钥，这就是为什么当我们第一次实现下载功能时，我们认为内容密钥是下载时需要，这导致我们在 iOS 10.2...

上浪费了一周

离线 Fairplay AVAssetDownloadTask 在下载时收到未知错误回调（只发生在 iOS 10.2）

Offline Fairplay AVAssetDownloadTask got unknown error callback while downloading (only happened on iOS 10.2)

fairplay

ios

swift

avassetdownloadtask