It is enough if VLC is in the task bar. It doesn't matter if a movie is playing or not.
No.
The problem isn't really solved, but since I know now that it is VLC player, I can turn it off. Then I don't have the problem. Because I didn't notice this at the beginning, so the question here in the forum. We can stop the discussion. It is good enough at it is.
Thank you. Sorry that I had a problem.