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

We propose new methods and architecture for low-delay, low-complexity video bit-rate reduction and continuous presence for multipoint videoconferencing. Rate reduction is performed in the discrete cosine transform (DCT) domain to achieve both low delay and low complexity. Requantization is applied to the originally quantized DCT coefficients, and the requantization errors are stored in a frame buffer in the DCT domain instead of the pixel domain. Skipped macroblocks in the original coded bitstream are processed to improve picture quality. The QCIP-to-CIF combiner is used to realize continuous presence. Asymmetric frame rates and pipelined combination on the group-of-blocks level lead to significantly reduced insertion delay compared to the published methods in the literature. Both simulation and real-time implementation results are reported to validate the proposed methods and architecture