No abstract

Layered coding architectures are attractive in theory for two reasons. FirsL they natur~y allow for heterogeneity in networks and receivers in terms of chent processing capabfity and network bandwidth. Second, they correspond to optim~ut~iation of avfiable bandwidth when seved video qutity Ievek are desired. b practice, the increased complexity imposed by the Iayering constraint can force the designer to do away with key parts of a coding algorithm, e.g. motion estimation for video coding. h this paper, we propose a salable sofware-ody video codec architecture with motion est"hnation, which is suitable for r~-tirne audio and video communication over packet network.Thecodingdgorithrnis compatiblewith~-T recommendation H.263+ and includes various techniques to reduce compIefity. Fast motionestiation @~) is performed at the H.263-compatibIe base layer and used at higher Iayers, and perceptual macroblock skipping is performed at dl layers before h~. SNR sdabfity * ,