为什么AVPlayer先下载而不是直播？

Question

我第一次使用 AVPlayer，我想使用带有实时流的 HTTP 请求播放 mp3 文件。我使用AVPlayer 可以正常播放mp3 文件，但问题是AVPlayer 需要先下载mp3 然后播放。我不知道为什么AVPlayer 下载文件然后播放而不是现场播放。我的 Xcode 8.2.1 和我正在使用 Swift 3。

这是我的代码 sn-p。

var audioPlayer = AVPlayer()
var avplayerItem : AVPlayerItem?

override func viewDidLoad() {
    super.viewDidLoad()

    let fileurl:URL = URL(string : "http://www.noiseaddicts.com/samples_1w72b820/2514.mp3")!
    avplayerItem = AVPlayerItem(url : fileurl)
    audioPlayer = AVPlayer(playerItem : avplayerItem)
    audioPlayer.rate = 1.0
    audioPlayer.play()
}

如果AVPlayer需要在播放前下载整个文件，音频直播应该怎么做？

谢谢。

Answer 1

另外编辑：Luaan 也是对的。 “直播需要服务器支持 - 至少能够进行部分下载。其他播放器是否允许使用该 URL 进行直播？”您还应该尝试使用未定义持续时间的声音 url。

您是否尝试过将其视为未定义持续时间的音频流？

  avplayerItem = CachingPlayerItem(url: url, recordingName: recordingName ?? "default.mp3")

CachingPlayerItem 将从 url 准备一个 AVURLAsset。

 init(url: URL, customFileExtension: String?, recordingName: String) {
    guard let components = URLComponents(url: url, resolvingAgainstBaseURL: false),
    let scheme = components.scheme,
    var urlWithCustomScheme = url.withScheme(cachingPlayerItemScheme) else {
    fatalError("Urls without a scheme are not supported")
    }
    self.recordingName = recordingName
    self.url = url
    self.initialScheme = scheme
    if let ext = customFileExtension {
    urlWithCustomScheme.deletePathExtension()
    urlWithCustomScheme.appendPathExtension(ext)
    self.customFileExtension = ext
    }
    let asset = AVURLAsset(url: urlWithCustomScheme)
    asset.resourceLoader.setDelegate(resourceLoaderDelegate, queue: DispatchQueue.main)
    super.init(asset: asset, automaticallyLoadedAssetKeys: nil)
    resourceLoaderDelegate.owner = self
    addObserver(self, forKeyPath: "status", options: NSKeyValueObservingOptions.new, context: nil)
    NotificationCenter.default.addObserver(self, selector: #selector(playbackStalledHandler), name:NSNotification.Name.AVPlayerItemPlaybackStalled, object: self)
    }

在 AVPlayerItem 初始化后，从它创建一个 AVPlayer 对象，以便它可以启动从给定 url 加载音频流的过程：

player = AVPlayer(playerItem: playerItem)
player.automaticallyWaitsToMinimizeStalling = false

func resourceLoader(_ resourceLoader: AVAssetResourceLoader, shouldWaitForLoadingOfRequestedResource loadingRequest: AVAssetResourceLoadingRequest) -> Bool {
if playingFromData {
// Nothing to load.
} else if session == nil {
// If we're playing from a url, we need to download the file.
// We start loading the file on first request only.
guard let initialUrl = owner?.url else {
fatalError("internal inconsistency")
}
startDataRequest(with: initialUrl)
}
pendingRequests.insert(loadingRequest)
processPendingRequests()
return true
}

安装资源后：

func startDataRequest(with url: URL) {
var recordingName = "default.mp3"
if let recording = owner?.recordingName{
recordingName = recording
}
fileURL = try! FileManager.default.url(for: .documentDirectory, in: .userDomainMask, appropriateFor: nil, create: false)
.appendingPathComponent(recordingName)
let configuration = URLSessionConfiguration.default
configuration.requestCachePolicy = .reloadIgnoringLocalAndRemoteCacheData
session = URLSession(configuration: configuration, delegate: self, delegateQueue: nil)
session?.dataTask(with: url).resume()
outputStream = OutputStream(url: fileURL, append: true)
outputStream?.schedule(in: RunLoop.current, forMode: RunLoopMode.defaultRunLoopMode)
outputStream?.open()
}

然后，开始将数据字节接收到委托函数中：

func urlSession(_ session: URLSession, dataTask: URLSessionDataTask, didReceive data: Data)

现在您已经开始接收实时音频流了。

func urlSession(_ session: URLSession, dataTask: URLSessionDataTask, didReceive data: Data) {
let bytesWritten = data.withUnsafeBytes{outputStream?.write($0, maxLength: data.count)}
print("bytes written :\(bytesWritten!) to \(fileURL)")
}

现在创建一个 OutputStream 对象，打开它，然后在上面的委托函数中附加我们接收到的字节，就是这样，我们保存了实时音频流的所需部分。

取自：Medium Article, Mohan Pandey