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