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 {HEAD ~ a plurality} of {TAIL ~ seconds} of 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 { HEAD ~ a plurality } of { TAIL ~ seconds } of 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 HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH