How do I solve this infinite-mirror-effect in this video

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C++

Visual-Studio

OpenCV

Hi, i have a task to capture desktop or activewindow using OPENCV as video source, but the result gives infinite-mirror-efect in the output video, someone says it have something to do with the GetDesktopWindow , also i have a function that create a bitmap from the screen image called hwnd2mat
this is inside main :

HWND hwndDesktop = GetDesktopWindow();	
	int key = 0;
	while (key != 30 )
	{
		Mat src = hwnd2mat(hwndDesktop);		
		// you can do some image processing here
		imshow("output", src);
		key = waitKey(30); // you can change wait time
	}
	ReleaseCapture();
	destroyAllWindows();
	return 0;

What I have tried:

i change GetDesktopWindow() with FindWindow() or FindWindowEx() and using Spy++ to find the Class of i don't know what, but i don't know example how i do that, could you please give me an example or a solution for this? appreciate it very much, i've been struggling with this for 2 days.