Basic Background Subtractor Producing black screen

[Q3Varnam]

public class BackgroundSubtractor
{
    static boolean capture = true;
    public static void main(String args[])
    {
        VideoCapture video;

        try
        {
            video = new VideoCapture(640, 480);
            final BasicBackgroundSubtract<MBFImage> background =new BasicBackgroundSubtract<MBFImage>();

            VideoDisplay<MBFImage> display = 

            VideoDisplay.createVideoDisplay(video);
            display.addVideoListener(new VideoDisplayListener<MBFImage>() {

                @Override
                public void beforeUpdate(MBFImage frame)
                {
                    if(capture)
                    {
                        System.out.println("Capturing background in 4 seconds");
                        try
                        {
                            Thread.sleep(4000);
                        }
                        catch (InterruptedException e)
                        {
                            // TODO Auto-generated catch block
                            e.printStackTrace();
                        }

                        background.setBackground(frame);
                        System.out.println("Captured");
                        capture =false;
                        return;
                    }
                    background.processImage(frame);
                }

                @Override
                public void afterUpdate(VideoDisplay<MBFImage> display)
                {
                    // TODO Auto-generated method stub

                }
            });
        } catch (VideoCaptureException e)
        {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }

    }
}

I am trying out the basic background subtract class as above. But this results in a black screen.

I try to capture the background when the app starts up and then insert a new object in the frame between the background and the camera expecting the inserted object will be visible.

Is my use case for this class correct?

[Jonathon Hare]

I think, your code is basically correct, but instead of sleeping for 4000ms, you'll need to capture a few frames to warm up the camera (the first frame will always be black). I'll try and post a code example in a bit.

[Q3Varnam]

Thanks for your fast response as usual, in the mean while I tried using it with two static images of same size, it does work but it produces the similar result as a image.subtract(image)

For video background subtraction, I tried your suggestion, it still didn't work. Then I realised may be frame is a reference.

Now I am using frame.clone() in

background.setBackground(frame.clone());

This works - but the background has lot of noise.