This is a bubble dot on a video nothing to do with the camera.What you have here is a focusing point. On the camera display this is the part that will be in focus when you take the photo. in fact, I'm willing to bet if you tap on the screen while the camera is active the dot will move. As to how to remove it, I don't know. My only Samsung device is a Galaxy S4 and it has long since stopped running stock builds.