Further, every time {HEAD ~ the child frame video} is switched freely between {TAIL ~ display} and non display, the child frame video can be synthesized for its display at an appropriate position 
is switched freely between
Further , every time { HEAD ~ the child frame video } is switched freely between { TAIL ~ display } and non display , the child frame video can be synthesized for its display at an appropriate position
OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL REL REL REL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH