1. A graphics detector device to detect one or more graphics layers which have been added into a video signal by a vision mixer, wherein the device comprises a processor and a memory and is configured to: receive the video signal from the vision mixer having the graphics layers added therein, and a first original image signal into which the graphics layers were added by the vision mixer to produce the video signal; establish a constant background signal which is shared with the vision mixer; obtain a second composite image signal having the graphics layers added into the constant background signal likewise to the video signal; derive a detected graphics signal from the video signal, the first original image signal, the constant background signal, and the second composite image signal, wherein the detected graphics signal represents the one or more graphics layers which have been added into the video signal; and output the detected graphics signal onto a tangible non-transient recording medium.