How to get IVideoWindow's HWND?

I want to create a button in the middle of the video screen.
To put the button, I need to get the HWND of Video Renderer window because
the button needs parent window's handle.
I checked methods in IVideoWindow but I cannot see any method to get the
HWND value.
Is there any way to get the HWND?
And, can I create a button on the video window if I get the window handle?

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