wherein metadata manages the time at which the displayed area of the second video is changed to {HEAD ~ a different position} in {TAIL ~ the first video}, 
wherein metadata manages the time at which the displayed area of the second video is changed to { HEAD ~ a different position } in { TAIL ~ the first video } ,
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH