Abstract: A system for adaptively transporting video over networks wherein the available bandwidth varies with time. The system comprises a video/audio codec that functions to compress, code, decode and decompress video streams that are transmitted over networks having available bandwidths that vary with time and location. Depending on the channel bandwidth, the system adjusts the compression ratio to accommodate a plurality of bandwidths ranging from 20 Kbps for POTS to several Mbps for switched LAN and ATM environments. Bandwidth adjustability is provided by offering a trade off between video resolution, frame rate and individual frame quality. The system generates a video data stream comprised of Key, P and B frames from a raw source of video. Each frame type is further comprised of multiple levels of data representing varying degrees of quality.

Abstract: A novel method of improving the motion estimation and coding efficiency of Interframes in a video compression system is disclosed. The method teaches a novel minimization function to be used to determine the optimum motion vector for a block within a picture. The minization function takes into account not just the conventional sum of the differences but also the quantization step, the motion vector itself and the predicted motion vector. The minimization function disclosed better balances the tradeoff between the size of the motion vectors and the size of the resulting residuals. The results are particularly useful when the range of the search is increased. Motion vectors closer to the prediction motion vector will be favored over better matches found further away from the prediction motion vector. In addition, a novel variable length coding (VLC) method is also disclosed.