a synthesizing portion for laying and synthesizing the second video over the displayed position inside {HEAD ~ the first video}, designated by {TAIL ~ the designating portion}, 
a synthesizing portion for laying and synthesizing the second video over the displayed position inside { HEAD ~ the first video } , designated by { TAIL ~ the designating portion } ,
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH REL REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH