Adaptive streaming

This article describes how to add playback of adaptive streaming multimedia content to a Universal Windows Platform (UWP) app. This feature supports playback of Http Live Streaming (HLS) and Dynamic Streaming over HTTP (DASH) content. Starting with Windows 10, version 1803, Smooth Streaming is supported by AdaptiveMediaSource.

For a list of supported HLS protocol tags, see HLS tag support.

For a list of supported DASH profiles, see DASH profile support.

Note

The code in this article was adapted from the UWP Adaptive streaming sample.

Simple adaptive streaming with MediaPlayer and MediaPlayerElement

To play adaptive streaming media in a UWP app, create a Uri object pointing to a DASH or HLS manifest file. Create an instance of the MediaPlayer class. Call MediaSource.CreateFromUri to create a new MediaSource object and then set that to the Source property of the MediaPlayer. Call Play to start playback of the media content.

MediaPlayer _mediaPlayer;
System.Uri manifestUri = new Uri("http://amssamples.streaming.mediaservices.windows.net/49b57c87-f5f3-48b3-ba22-c55cfdffa9cb/Sintel.ism/manifest(format=m3u8-aapl)");
_mediaPlayer = new MediaPlayer();
_mediaPlayer.Source = MediaSource.CreateFromUri(manifestUri);
_mediaPlayer.Play();

The above example will play the audio of the media content but it doesn't automatically render the content in your UI. Most apps that play video content will want to render the content in a XAML page. To do this, add a MediaPlayerElement control to your XAML page.

<MediaPlayerElement x:Name="mediaPlayerElement" HorizontalAlignment="Stretch" AreTransportControlsEnabled="True"/>

Call MediaSource.CreateFromUri to create a MediaSource from the URI of a DASH or HLS manifest file. Then set the Source property of the MediaPlayerElement. The MediaPlayerElement will automatically create a new MediaPlayer object for the content. You can call Play on the MediaPlayer to start playback of the content.

System.Uri manifestUri = new Uri("http://amssamples.streaming.mediaservices.windows.net/49b57c87-f5f3-48b3-ba22-c55cfdffa9cb/Sintel.ism/manifest(format=m3u8-aapl)");
mediaPlayerElement.Source = MediaSource.CreateFromUri(manifestUri);
mediaPlayerElement.MediaPlayer.Play();

Note

Starting with Windows 10, version 1607, it is recommended that you use the MediaPlayer class to play media items. The MediaPlayerElement is a lightweight XAML control that is used to render the content of a MediaPlayer in a XAML page. The MediaElement control continues to be supported for backwards compatibility. For more information about using MediaPlayer and MediaPlayerElement to play media content, see Play audio and video with MediaPlayer. For information about using MediaSource and related APIs to work with media content, see Media items, playlists, and tracks.

Adaptive streaming with AdaptiveMediaSource

If your app requires more advanced adaptive streaming features, such as providing custom HTTP headers, monitoring the current download and playback bitrates, or adjusting the ratios that determine when the system switches bitrates of the adaptive stream, use the AdaptiveMediaSource object.

The adaptive streaming APIs are found in the Windows.Media.Streaming.Adaptive namespace. The examples in this article use APIs from the following namespaces.

using Windows.Media.Streaming.Adaptive;
using System.Threading.Tasks;
using Windows.Storage.Streams;
using Windows.Media.Playback;
using Windows.Media.Core;

Initialize an AdaptiveMediaSource from a URI.

Initialize the AdaptiveMediaSource with the URI of an adaptive streaming manifest file by calling CreateFromUriAsync. The AdaptiveMediaSourceCreationStatus value returned from this method lets you know if the media source was created successfully. If so, you can set the object as the stream source for your MediaPlayer by creating a MediaSource object by calling MediaSource.CreateFromAdaptiveMediaSource, and then assigning it to the media player's Source property. In this example, the AvailableBitrates property is queried to determine the maximum supported bitrate for this stream, and then that value is set as the inital bitrate. This example also registers handlers for the several AdaptiveMediaSource events that are discussed later in this article.

async private void InitializeAdaptiveMediaSource(System.Uri uri)
{
    AdaptiveMediaSourceCreationResult result = await AdaptiveMediaSource.CreateFromUriAsync(uri);

    if (result.Status == AdaptiveMediaSourceCreationStatus.Success)
    {
        ams = result.MediaSource;
        mediaPlayerElement.SetMediaPlayer(new MediaPlayer());
        mediaPlayerElement.MediaPlayer.Source = MediaSource.CreateFromAdaptiveMediaSource(ams);
        mediaPlayerElement.MediaPlayer.Play();


        ams.InitialBitrate = ams.AvailableBitrates.Max<uint>();

        //Register for download requests
        ams.DownloadRequested += DownloadRequested;

        //Register for download failure and completion events
        ams.DownloadCompleted += DownloadCompleted;
        ams.DownloadFailed += DownloadFailed;

        //Register for bitrate change events
        ams.DownloadBitrateChanged += DownloadBitrateChanged;
        ams.PlaybackBitrateChanged += PlaybackBitrateChanged;

        //Register for diagnostic event
        ams.Diagnostics.DiagnosticAvailable += DiagnosticAvailable;
    }
    else
    {
        // Handle failure to create the adaptive media source
        MyLogMessageFunction($"Adaptive source creation failed: {uri} - {result.ExtendedError}");
    }
}



Initialize an AdaptiveMediaSource using HttpClient

If you need to set custom HTTP headers for getting the manifest file, you can create an HttpClient object, set the desired headers, and then pass the object into the overload of CreateFromUriAsync.

httpClient = new Windows.Web.Http.HttpClient();
httpClient.DefaultRequestHeaders.TryAppendWithoutValidation("X-CustomHeader", "This is a custom header");
AdaptiveMediaSourceCreationResult result = await AdaptiveMediaSource.CreateFromUriAsync(manifestUri, httpClient);

The DownloadRequested event is raised when the system is about to retrieve a resource from the server. The AdaptiveMediaSourceDownloadRequestedEventArgs passed into the event handler exposes properties that provide information about the resource being requested such as the type and URI of the resource.

Modify resource request properties using the DownloadRequested event

You can use the DownloadRequested event handler to modify the resource request by updating the properties of the AdaptiveMediaSourceDownloadResult object provided by the event args. In the example below, the URI from which the resource will be retrieved is modified by updating the ResourceUri properties of the result object. You can also rewrite the byte range offset and length for media segments or, as shown the example below, change the resource URI to download the full resource and set the byte range offset and length to null.

You can override the content of the requested resource by setting the Buffer or InputStream properties of the result object. In the example below, the contents of the manifest resource are replaced by setting the Buffer property. Note that if you are updating the resource request with data that is obtained asynchronously, such as retrieving data from a remote server or asynchronous user authentication, you must call AdaptiveMediaSourceDownloadRequestedEventArgs.GetDeferral to get a deferral and then call Complete when the operation is complete to signal the system that the download request operation can continue.

    private async void DownloadRequested(AdaptiveMediaSource sender, AdaptiveMediaSourceDownloadRequestedEventArgs args)
    {

        // rewrite key URIs to replace http:// with https://
        if (args.ResourceType == AdaptiveMediaSourceResourceType.Key)
        {
            string originalUri = args.ResourceUri.ToString();
            string secureUri = originalUri.Replace("http:", "https:");

            // override the URI by setting property on the result sub object
            args.Result.ResourceUri = new Uri(secureUri);
        }

        if (args.ResourceType == AdaptiveMediaSourceResourceType.Manifest)
        {
            AdaptiveMediaSourceDownloadRequestedDeferral deferral = args.GetDeferral();
            args.Result.Buffer = await CreateMyCustomManifest(args.ResourceUri);
            deferral.Complete();
        }

        if (args.ResourceType == AdaptiveMediaSourceResourceType.MediaSegment)
        {
            var resourceUri = args.ResourceUri.ToString() + "?range=" + 
                args.ResourceByteRangeOffset + "-" + (args.ResourceByteRangeLength - 1);

            // override the URI by setting a property on the result sub object
            args.Result.ResourceUri = new Uri(resourceUri);

            // clear the byte range properties on the result sub object
            args.Result.ResourceByteRangeOffset = null;
            args.Result.ResourceByteRangeLength = null;
        }
    }

Use bitrate events to manage and respond to bitrate changes

The AdaptiveMediaSource object provides events that allow you to react when the download or playback bitrates change. In this example, the current bitrates are simply updated in the UI. Note that you can modify the ratios that determine when the system switches bitrates of the adaptive stream. For more information, see the AdvancedSettings property.

private async void DownloadBitrateChanged(AdaptiveMediaSource sender, AdaptiveMediaSourceDownloadBitrateChangedEventArgs args)
{
    await this.Dispatcher.RunAsync(CoreDispatcherPriority.Normal, new DispatchedHandler(() =>
    {
        txtDownloadBitrate.Text = args.NewValue.ToString();
    }));
}

private async void PlaybackBitrateChanged(AdaptiveMediaSource sender, AdaptiveMediaSourcePlaybackBitrateChangedEventArgs args)
{
    await this.Dispatcher.RunAsync(CoreDispatcherPriority.Normal, new DispatchedHandler(() =>
    {
        txtPlaybackBitrate.Text = args.NewValue.ToString();
    }));
}

Handle download completion and failure events

The AdaptiveMediaSource object raises the DownloadFailed event when the download of a requested resource fails. You can use this event to update your UI in response to the failure. You can also use the event to log statistical information about the download operation and the failure.

The AdaptiveMediaSourceDownloadFailedEventArgs object passed into the event handler contains metadata about the failed resource download, such as the resource type, the URI of the resource, and the position within the stream where the failure occurred. The RequestId gets a system-generated unique identifier for the request that can be use to correlate status information about an individual request across multiple events.

The Statistics property returns a AdaptiveMediaSourceDownloadStatistics object which provides detailed information about the number of bytes received at the time of the event and the timing of various milestones in the download operation. You can log this information in order identify perfomance issues in your adaptive streaming implementation.

private void DownloadFailed(AdaptiveMediaSource sender, AdaptiveMediaSourceDownloadFailedEventArgs args)
{
    var statistics = args.Statistics;

    MyLogMessageFunction("download failed for: " + args.ResourceType + 
     " - " + args.ResourceUri +
     " – Error:" + args.ExtendedError.HResult +
     " - RequestId" + args.RequestId + 
     " – Position:" + args.Position +
     " - Duration:" + args.ResourceDuration +
     " - ContentType:" + args.ResourceContentType +
     " - TimeToHeadersReceived:" + statistics.TimeToHeadersReceived + 
     " - TimeToFirstByteReceived:" + statistics.TimeToFirstByteReceived + 
     " - TimeToLastByteReceived:" + statistics.TimeToLastByteReceived +
     " - ContentBytesReceivedCount:" + statistics.ContentBytesReceivedCount);

}

The DownloadCompleted event occurs when a resource download completes and provdes similar data to the DownloadFailed event. Once again, a RequestId is provided for correlating events for a single request. Also, an AdaptiveMediaSourceDownloadStatistics object is provided to enable logging of download stats.

private void DownloadCompleted(AdaptiveMediaSource sender, AdaptiveMediaSourceDownloadCompletedEventArgs args)
{
    var statistics = args.Statistics;

    MyLogMessageFunction("download completed for: " + args.ResourceType + " - " +
     args.ResourceUri +
     " – RequestId:" + args.RequestId +
     " – Position:" + args.Position +
     " - Duration:" + args.ResourceDuration +
     " - ContentType:" + args.ResourceContentType +
     " - TimeToHeadersReceived:" + statistics.TimeToHeadersReceived + 
     " - TimeToFirstByteReceived:" + statistics.TimeToFirstByteReceived + 
     " - TimeToLastByteReceived:" + statistics.TimeToLastByteReceived +
     " - ContentBytesReceivedCount:" + statistics.ContentBytesReceivedCount);

}

Gather adaptive streaming telemetry data with AdaptiveMediaSourceDiagnostics

The AdaptiveMediaSource exposes a Diagnostics property which returns an AdaptiveMediaSourceDiagnostics object. Use this object to register for the DiagnosticAvailable event. This event is intended to be used for telemetry collection and should not be used to modify app behavior at runtime. This diagnostic event is raised for many different reasons. Check the DiagnosticType property of the AdaptiveMediaSourceDiagnosticAvailableEventArgs object passed into the event to determine the reason that the event was raised. Potential reasons include errors accessing the requested resource and errors parsing the streaming manifest file. For a list of situations that can trigger a diagnostic event, see AdaptiveMediaSourceDiagnosticType. Like the arguments for other adaptive streaming events, the AdaptiveMediaSourceDiagnosticAvailableEventArgs provides a RequestId propery for correlating request information between different events.

private void DiagnosticAvailable(AdaptiveMediaSourceDiagnostics sender, AdaptiveMediaSourceDiagnosticAvailableEventArgs args)
{
    MySendTelemetryFunction(args.RequestId, args.Position,
                            args.DiagnosticType, args.SegmentId,
                            args.ResourceType, args.ResourceUri,
                            args.ResourceDuration, args.ResourceContentType,
                            args.ResourceByteRangeOffset,
                            args.ResourceByteRangeLength, 
                            args.Bitrate,
                            args.ExtendedError);

}

Defer binding of adaptive streaming content for items in a playback list by using MediaBinder

The MediaBinder class allows you to defer binding of media content in a MediaPlaybackList. Starting with Windows 10, version 1703, you can supply an AdaptiveMediaSource as bound content. The process for deferred binding of an adaptive media source is largely the same as binding other types of media, which is described in Media items, playlists, and tracks.

Create a MediaBinder instance, set an app-defined Token string to identify the content to be bound, and register for the Binding event. Create a MediaSource from the Binder by calling MediaSource.CreateFromMediaBinder. Then, create a MediaPlaybackItem from the MediaSource and add it to the playback list.

_mediaPlaybackList = new MediaPlaybackList();

var binder = new MediaBinder();
binder.Token = "MyBindingToken1";
binder.Binding += Binder_Binding;
_mediaPlaybackList.Items.Add(new MediaPlaybackItem(MediaSource.CreateFromMediaBinder(binder)));

binder = new MediaBinder();
binder.Token = "MyBindingToken2";
binder.Binding += Binder_Binding;
_mediaPlaybackList.Items.Add(new MediaPlaybackItem(MediaSource.CreateFromMediaBinder(binder)));

_mediaPlayer = new MediaPlayer();
_mediaPlayer.Source = _mediaPlaybackList;
mediaPlayerElement.SetMediaPlayer(_mediaPlayer);

In the Binding event handler, use the token string to identify the content to be bound and then create the adaptive media source by calling one of the overloads of CreateFromStreamAsync or CreateFromUriAsync. Because these are asynchronous methods, you should first call the MediaBindingEventArgs.GetDeferral method to instruct the system to wait for your operation to complete before continuing. Set the adaptive media source as the bound content by calling SetAdaptiveMediaSource. Finally, call Deferral.Complete after your operation is complete to instruct the system to continue.

private async void Binder_Binding_AdaptiveMediaSource(MediaBinder sender, MediaBindingEventArgs args)
{
    var deferral = args.GetDeferral();

    var contentUri = new Uri($"http://contoso.com/media/{args.MediaBinder.Token}");
    AdaptiveMediaSourceCreationResult result = await AdaptiveMediaSource.CreateFromUriAsync(contentUri);

    if (result.MediaSource != null)
    {
        args.SetAdaptiveMediaSource(result.MediaSource);
    }
    args.SetUri(contentUri);

    deferral.Complete();
}

If you want to register event handlers for the bound adaptive media source, you can do this in the handler for the CurrentItemChanged event of the MediaPlaybackList. The CurrentMediaPlaybackItemChangedEventArgs.NewItem property contains the new currently playing MediaPlaybackItem in the list. Get an instance of the AdaptiveMediaSource representing the new item by accessing the Source property of the MediaPlaybackItem and then the AdaptiveMediaSource property of the media source. This property will be null if the new playback item is not an AdaptiveMediaSource, so you should test for null before attempting to register handlers for any of the object's events.

private void AMSMediaPlaybackList_CurrentItemChanged(MediaPlaybackList sender, CurrentMediaPlaybackItemChangedEventArgs args)
{
    if (!(args.NewItem is null))
    {
        var ams = args.NewItem.Source.AdaptiveMediaSource;
        if (!(ams is null))
        {
            ams.PlaybackBitrateChanged += Ams_PlaybackBitrateChanged;
        }
    }
}