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