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