Detecting physical presence or behaviour of the user

Official title: {Detecting physical presence or behaviour of the user, e.g. using sensors to detect if the user is leaving the room or changes his face expression during a TV programme (methods or arrangements for recognising human body or animal bodies or body parts G06V40/10; methods or arrangements for acquiring or recognising human faces, facial parts, facial sketches, facial expressions G06V40/16; methods or arrangements for recognising movements or behaviour G06V40/20; arrangements for identifying users in broadcast systems H04H60/45)}

H04N21/44218 (Detecting physical presence or behaviour of the user) appears on 2,774 US grants and 3,712 published applications in this corpus.