Adaptive quadtree coding of motion-compensated image sequences for use on the broadband ISDN
An image-coding technique is described in which an adaptive quadtree scheme is used to encode motion-compensated difference images. A mechanism is determined within the encoding process that allows a predetermined level of image quality to be selected by the user at call setup time and then maintained by the encoder. The coder operates in a variable-bit-rate mode providing a video service of near-constant image quality. A multilayered version of the coding scheme is also described in which the degradation caused by cell loss during transmission can be limited in its effect and removed completely within a short period of time. The recovery from cell loss is achieved by sending blocks from the original image sequence whenever cells are known to have been deleted by the local-network access node. >