Aperture of a movie

Builder
1

Hi,
I’m trying to use the “Aperture Component” to show only a part of a movie, I am setting the size of the aperture to 120 pix, setting its position to [500,500] pix and setting its start to the start of the movie, but when I’m trying to run the experiment, A grey screen is appearing instead of the movie with the mask.
what can I do?

thank you,
nophar

2

What is the size/location of the movie? i.e. does an aperture location of 500 pixels to the right of centre and 500 pixels above centre actually reflect where you intended it to be?