how can i composite a shadows or reflections on to a media plate using composure?

I’m trying to output the result using Black magic decklink. but it does not work

here are some references to what i’m aiming for.

here is my attempts trying to create mixed reality in a sport television show by spawning player cards on the studio set, the floor in the studio is reflective epoxy and the augmented reality will look more realistic if it had reflection cast as well when outputting it to the decklink