accessing a random access memory as a primary storage medium on a realtime basis for recording/playing back video data from/to a video device, the random access memory having a large capacity to store a plurality of frames of video data representing {TAIL ~ a plurality} of seconds of {HEAD ~ video data}; and 
accessing a random access memory as a primary storage medium on a realtime basis for recording / playing back video data from / to a video device , the random access memory having a large capacity to store a plurality of frames of video data representing { TAIL ~ a plurality } of seconds of { HEAD ~ video data } ; and
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH