Getting Thumbnail from Video using MediaPlayer Class in WPF

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• Download source - 18.2 KB

Introduction

I once needed to create thumbnails of videos to be used in a WPF application. First, I thought of using FFMPEG to get the job done, but then changed my mind and used System.Windows.Media.MediaPlayer after doing some search on the Internet.

I owe thanks to all the people from different places on the Internet from whom I derived this version of my application. I do not remember the places from where I had taken the code snippets. But I am thankful to all of them anyway!

To make things more interesting, the sample code creates thumbnails using multi-threading. We also show a nice animation while the thumbnail creation process is in progress.

MediaElement is a bit sluggish and takes some time before the video is loaded and we have to wait a little before acquiring the thumbnail. Unfortunately, the time to wait is quite arbitrary and varies from machine to machine and invocation to invocation. So I have provided a combo-box to change the wait time if the default does not work. I have also provided another combo-box to select the position in seconds from the start of the video to specify the time when the screenshot should be taken.

Here is a screenshot of the sample application at work:

The Code

Following is a simplified version of the accompanying sample application. I have placed comments where needed. The sample application is multi-threaded and uses just a little more elaborate code. Please see the sample code for more details.

void ImportMedia(string mediaFile, int waitTime, int position)
{
    MediaPlayer player = new MediaPlayer { Volume = 0, ScrubbingEnabled = true };
    player.Open(new Uri(mediaFile));
    player.Pause();
    player.Position = TimeSpan.FromSeconds(position);
    //We need to give MediaPlayer some time to load. 
    //The efficiency of the MediaPlayer depends                 
    //upon the capabilities of the machine it is running on and 
    //would be different from time to time
    System.Threading.Thread.Sleep(waitTime * 1000);

    //120 = thumbnail width, 90 = thumbnail height and 96x96 = horizontal x vertical DPI
    //In an real application, you would not probably use hard coded values!
    RenderTargetBitmap rtb = new RenderTargetBitmap(120, 90, 96, 96, PixelFormats.Pbgra32);
    DrawingVisual dv = new DrawingVisual();
    using (DrawingContext dc = dv.RenderOpen())
    {
        dc.DrawVideo(player, new Rect(0, 0, 120, 90));
    }
    rtb.Render(dv);
    Duration duration = player.NaturalDuration;
    int videoLength = 0;
    if (duration.HasTimeSpan)
    {
        videoLength = (int)duration.TimeSpan.TotalSeconds;
    }
    BitmapFrame frame = BitmapFrame.Create(rtb).GetCurrentValueAsFrozen() as BitmapFrame;
    BitmapEncoder encoder = new JpegBitmapEncoder();
    encoder.Frames.Add(frame as BitmapFrame);
    MemoryStream memoryStream = new MemoryStream();
    encoder.Save(memoryStream);
    //Here we have the thumbnail in the MemoryStream!
    player.Close();
}