as information to be processed at an object - based video or audio - visual terminal , an object - oriented bitstream includes objects , composition information , and scene demarcation information . such bitstream structure allows on - line editing , e . g . cut and paste , insertion / deletion , grouping , and special effects . in the interest of ease of editing , av objects and their composition information are transmitted or accessed on separate logical channels . objects which have a lifetime in the decoder beyond their initial presentation time are cached for reuse until a selected expiration time . the system includes a de - multiplexer , a controller which controls the operation of the av terminal , input buffers , av objects decoders , buffers for decoded data , a composer , a display , and an object cache .