Question

My application applies custom HLSL shader effects to a mediaElement using decorators. How can I record and save the modified video using the application itself in realtime?

Answer 1

I have been using the RenderTargetBitmap object to render image sequences of animations like this:

First you call:

myStoryboard.CurrentTimeInvalidated += new EventHandler(onCurrentTimeInvalidated );

where myStoryboard is the Storyboard driving the animation and then you have the following method:

void onCurrentTimeInvalidated (object sender, EventArgs e)
        {
            prefix = "";
            if (counter < 10)
            {
                prefix = "000";
            }
            else if (counter < 100)
            {
                prefix = "00";
            }
            else if (counter < 1000)
            {
                prefix = "0";
            }

            Size size = new Size(MainCanvas.ActualWidth, MainCanvas.ActualHeight);
            MainCanvas.Measure(size);
            MainCanvas.Arrange(new Rect(size));


            RenderTargetBitmap bmp = new RenderTargetBitmap(imgWidth, imgHeight, 96d, 96d, PixelFormats.Default);
            bmp.Render(MainCanvas);

            JpegBitmapEncoder encoder = new JpegBitmapEncoder();
            encoder.QualityLevel = 90;
            encoder.Frames.Add(BitmapFrame.Create(bmp));
            string file = basePath + prefix + counter.ToString() + "_testpic.jpg";
            using (Stream stm = File.Create(file))
            {
                encoder.Save(stm);
            }
            counter++;
        }

I am not sure how well this will work with the MediaElement but it may be worth a try. For this to work on the MediaElement though you need to drive the MediaElement from a MediaTimeline and call the onCurrentTimeInvalidated method from it’s CurrentTimeInvalidated event.