Abstract: A de-framer (72) in a communications gateway (22) translates videoconferencing information from a circuit-switched format to a packet-switched format. A demultiplexor (78) extracts a bitstream containing video information that includes error-correction-code fields disposed at predetermined locations with respect to synchronization bits spaced by a synchronization interval and forming a predetermined synchronization sequence. A frame checker (88) for checking the error-correction code finds codeword boundaries by comparing the predetermined synchronization sequence with sequences of synchronization-interval-spaced video-bitstream bits until it finds a match. To do so, the frame checker (88) takes a group of video-bitstream words offset from each other by the synchronization interval. It compares each word in the group with a respective synchronization word consisting of a word-width replication of a respective synchronization bit.

Abstract: In a multipoint control unit for conferencing audiovisual terminals, conference participants are greeted with audio and video welcome messages and then placed in an automated queue. The automated queue is a holding queue from which a conference operator can select the next available conference participant in the queue and conduct a subconference. Apparatus in the multipoint control unit includes a memory for storing video data and a processor coupled to the memory for controlling playback of the video data to a connected terminal during conference setup.

Abstract: A centralized multipoint conferencing arrangement uses a combination of multicast and unicast transmissions that is bandwidth efficient. A method of conferencing includes transmitting multimedia streams from endpoint terminals to a central resource such as a multipoint control unit (MCU) using unicast transmission. The multimedia streams are processed in the MCU and transmitted back to the endpoint terminals using multicast transmission. In addition, the MCU transmits other multimedia streams to selected endpoint terminals using unicast transmission. At the selected endpoint terminals, processing of the multimedia streams is inhibited in favor of processing the other multimedia streams.

Abstract: In a multipoint control unit for conferencing audiovisual terminals, conference participants are greeted with audio and video welcome messages and then placed in an automated queue. The automated queue is a holding queue from which a conference operator can select the next available conference participant in the queue and conduct a subconference. Apparatus in the multipoint control unit includes a memory for storing video data and a processor coupled to the memory for controlling playback of the video data to a connected terminal during conference setup.

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.

Abstract: A split bus arrangement for increasing network interface bandwidth capacity in a multipoint control unit includes a bus clock circuit for passing clock signals from a first network bus to a second network bus over a common interprocessor bus. A preferred timing arrangement provides frequency and phase lock among processor units communicating on the common interprocessor bus.

Abstract: An apparatus and method for replacing circuit boards in a live communication system having an over-the-top ribbon cable data bus configuration. The ribbon cables are segmented and redirected between individual circuit boards and a backplane data bus. Each ribbon cable connects either directly to the backplane or to an interposer board coupled between the circuit board and the backplane. Isolation circuitry either on the backplane or on the interposer board isolates clock and data signals between the backplane and a circuit board selected for replacement.

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.