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