Most current digital video systems merely replace existing modes of analog video delivery with their more efficient digital counterparts. However, as packet-based networks, such as the Internet, start to be an essential component of the communications infrastructure and general purpose computers become the predominant communication terminal, there is a need to provide a new set of algorithms for video compression and processing, which are optimized for an endto- end software processing environment. The challenge is then to find efficient ways of embedding video data on a fundamentally asynchronous transmission/processing infrastructure. To address this challenge this project concentrates on two main areas: (i) computation/bandwidth scalable coding and (ii) robust asynchronous video transmission algorithms. The Internet is a heterogeneous network, both in terms of its components (hosts, routers) and in terms of available bandwidth and processing speed. Thus bandwidth/computation scalable algorithms are desirable to enable less complex encoding/decoding at the expense of a reduction in video quality. This project is developing a design methodology for variable complexity, input dependent coding/decoding algorithms where the goal is optimizing average (instead of "worst-case") complexity performance, robust asynchronous video transmission algorithms are also being developed, as motivated by the limited transmission reliability offered by the Internet. Video is sensitive not only to losses of information (e.g. packets being dropped due to congestion) but also to excessive delay. This work concentrates on new compression techniques for asynchronous video transmission where each video unit (a part of a frame) has a ``lifetime'' during which it is useful, and which can span more than a single frame time interval. This area includes novel work in both rate control and image domain error correction/detection techniques.
