Patent ID: 8175154

Claim:
An apparatus for encoding a signal comprising picture information defining a group of pictures, said apparatus comprising: an input device for receiving picture information, said picture information comprising I picture information and P picture information; an output device for transmitting a signal comprising compressed picture information; a processing unit; and, a memory, said memory including a program module containing instructions for said processing unit operative to: compress I picture information utilizing an intra-coding process; and, compress P picture information utilizing past reference picture information; wherein selected P picture information references a number of past reference pictures, the number of past reference pictures being based on whether a current picture P is reference by a future picture according to the restriction, such that, if the current P picture is reference by a future picture, pictures temporally prior to an I picture which is temporally prior to the current picture are not permitted to be used as reference pictures, and if the current P picture is not referenced by a future picture, pictures temporally prior to an I picture which is temporally prior to the current picture are permitted to be used as reference pictures.