Group-of-block based video signal combining for multipoint continuous presence video conferencing
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An apparatus and method for combining video signals from multiple users in a continuous presence video conferencing system. Video signals are received from each of a number of different system users. The signals include input frames each having a number of different groups-of-blocks (GOBs). The GOBs correspond to hierarchically organized video data and header information. The input frame GOBs are used to form a composite output video signal suitable for transmission to each of the system users. An output frame of the composite output signal incorporates at least one of the GOBs from the input frames of each of the users and less than all of the GOBs from the input frame of at least one of the users. The resulting output video signal provides flexible continuous presence video conferencing in which video signals from multiple users may be simultaneously displayed to all users in a selected divided-screen format. The input frames may be Quarter Common Intermediate Format (QCIF) frames and the output frames may be Common Intermediate Format (CIF) frames in accordance with the H.261 video coding standard.