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