Capture card, image from the capture card appears on top

[gramoteous]

Hi all. Please help me solve the problem. I have a decklink sdi 4k board and a computer with windows. I set up the scene in OBS Studio: the background is a media source (the video file is looped) and the capture source is the Decklink board on top. How to make it so that if there is no signal on the board, then only the background is displayed, and when a signal appears on the board, the picture for reception is activated (in case of signal loss, only the background is played).
Thanks!

 

[gramoteous]

Or how to make the decklink source transparent when there is no signal (currently there is a black field when there is no signal) ?