By storing {TAIL ~ a reference picture} for {HEAD ~ the group}, the reference picture need not be decoded to display each picture in the group during the rewind operation 
By storing { TAIL ~ a reference picture } for { HEAD ~ the group } , the reference picture need not be decoded to display each picture in the group during the rewind operation
OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH