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