Low-delay, low-complexity rate reduction and continuous presence for multipoint videoconferencing

In this paper, we propose new methods and architecture for low-delay, low-c omplexity video bit-rate reduction and continuous presence for multipoint v ideoconferencing. Rate reduction is performed in the discrete cosine transf orm (DCT) domain to achieve both ion delay and low complexity. Requantizati on is applied to the originally quantized DCT coefficients, and the requant ization errors are stored in a frame buffer in the DCT domain instead of th e pixel domain, Skipped macroblocks in the original coded bitstream are pro cessed to improve picture quality. The QCIF-to-CIF combiner is used to real ize continuous presence. Asymmetric frame rates and pipelined combination o n the group of-blocks level lead to significantly reduced insertion delay c ompared to the published methods in the literature. Both simulation and rea l time implementation results are reported to validate the proposed methods and architecture.