Video teleconferencing system with digital transcoding

Abstract

A video teleconferencing system uses digital transcoding to obtain algorithm transcoding, transmission rate matching, and spatial mixing. The video teleconferencing system comprises a multipoint control unit (MCU) for allowing multiple audiovisual terminals, which send and receive compressed digital data signals, to communicate with each other in a conference. The MCU has a video processing unit (VPU) that performs algorithm transcoding, rate matching, and spatial mixing among the terminals within a conference. The VPU includes a time division multiplex pixel bus and a plurality of processors. Each processor is assignable to an audiovisual terminal in the conference and is coupled to the pixel bus. In a receive mode, each processor receives and decodes compressed video signals from its assigned terminal and puts the decoded signal onto the pixel bus. In a transmit mode, each processor receives from the pixel bus uncompressed video signals from any terminal in the conference. The uncompressed video signals are processed and encoded for transmission to the respective assigned terminal. Video encoding time due to motion displacement search is reduced by passing displacement information from the compressed video signals to the encoder to be used directly or as a seed for further refinements of the motion displacement field.