AVPlayer 可以从 API 端点正确传输视频文件吗？

我有一个 Xamarin iOS 应用程序，我想从支持 HTTP 范围请求的 API 端点流式传输视频。我已经在这里查看了许多类似的问题，但无论我尝试什么，我似乎都无法让 AVPlayer 在完全下载之前开始播放视频文件。 我试过了：

• KVO on playbackLikelyToKeepUp, playbackBufferEmpty and playbackBufferEmpty尽快播放视频ReadyToPlay
• set AutomaticallyWaitsToMinimizeStalling= 在 AVPlayer 上为 false
• set CanUseNetworkResourcesForLiveStreamingWhilePaused= 正确，并且PreferredForwardBufferDurationAVPlayerItem 上 = 1
• called PlayImmediatelyAtRate(1)在 AVPlayer 上

但文件仍然在视频开始播放之前完全下载，这会导致用户延迟。

是否可以让 AVPlayer 在完成下载之前开始播放视频文件，类似于 HTML 视频标签的做法？

这是我当前的代码：

    private void SetUpPlayer()
    {
        if (ViewModel.VideoStreamUrl == null)
        {
            return;
        }

        // See https://stackoverflow.com/questions/38865797/how-to-play-video-with-avplayerviewcontroller-avkit-in-xamarin-ios
        _aVPlayerItem = new AVPlayerItem(ViewModel.VideoStreamUrl)
        {
            CanUseNetworkResourcesForLiveStreamingWhilePaused = true,
            PreferredForwardBufferDuration = 1,
        };

        // See https://stackoverflow.com/questions/38867190/how-can-i-check-if-my-avplayer-is-buffering/38867386#38867386
        _playbackLikelyToKeepUpObserver?.Dispose();
        _playbackLikelyToKeepUpObserver = (NSObject)_aVPlayerItem.AddObserver("playbackLikelyToKeepUp",
            NSKeyValueObservingOptions.New,
            AVPlayerItem_BufferUpdated);

        _playbackBufferEmptyObserver?.Dispose();
        _playbackBufferEmptyObserver = (NSObject)_aVPlayerItem.AddObserver("playbackBufferEmpty",
            NSKeyValueObservingOptions.New,
            AVPlayerItem_BufferUpdated);

        _playbackBufferFullObserver?.Dispose();
        _playbackBufferFullObserver = (NSObject)_aVPlayerItem.AddObserver("playbackBufferFull",
            NSKeyValueObservingOptions.New,
            AVPlayerItem_BufferUpdated);

        _aVPlayer = new AVPlayer(_aVPlayerItem)
        {
            AutomaticallyWaitsToMinimizeStalling = false,
        };

        var playerViewController = new AVPlayerViewController
        {
            Player = _aVPlayer,
        };

        AddChildViewController(playerViewController);
        View.AddSubview(playerViewController.View);
        playerViewController.View.Frame = View.Frame;
        playerViewController.ShowsPlaybackControls = true;

        _aVPlayer.PlayImmediatelyAtRate(1);
    }

    private void AVPlayerItem_BufferUpdated(NSObservedChange obj)
    {
        ReportVideoBuffering();
    }

    private void ReportVideoBuffering()
    {
        bool isBufferEmpty = _aVPlayerItem != null && _aVPlayerItem.PlaybackBufferEmpty;
        Console.WriteLine($"Buffer empty? {isBufferEmpty}");
        Console.WriteLine($"Player status? {_aVPlayer.Status}");

        if (_aVPlayer.Status == AVPlayerStatus.ReadyToPlay)
        {
            Console.WriteLine($"Playing video.");
            _aVPlayer.Play();
        }
    }

这个问题的简单答案是否定的，AVPlayer 不支持使用 http 范围请求和部分内容 (206) 响应的流式传输。在我们的例子中，我们决定使用 Azure 媒体服务来提供流端点，然后我们可以在 iPad 应用程序以及 Web 上使用该端点。