Video teleconferencing system with digital transcoding
DCFirst Claim
1. A multipoint control unit for receiving compressed video signals from terminals in a conference and for transmitting selected compressed video signals to the terminals, the multipoint control unit comprising:
- a plurality of decoders, each decoder for decoding the compressed video signals from respective terminals to uncompressed video signals in a pixel domain;
a pixel bus receiving the uncompressed video signals at timeslots associated with respective terminals;
a selector for selecting the uncompressed video signals from one or more timeslots of the pixel bus; and
a plurality of encoders, each encoder for encoding the selected uncompressed video signals for transmission to respective terminals.
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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.
190 Citations
20 Claims
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1. A multipoint control unit for receiving compressed video signals from terminals in a conference and for transmitting selected compressed video signals to the terminals, the multipoint control unit comprising:
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a plurality of decoders, each decoder for decoding the compressed video signals from respective terminals to uncompressed video signals in a pixel domain; a pixel bus receiving the uncompressed video signals at timeslots associated with respective terminals; a selector for selecting the uncompressed video signals from one or more timeslots of the pixel bus; and a plurality of encoders, each encoder for encoding the selected uncompressed video signals for transmission to respective terminals. - View Dependent Claims (2, 3, 4, 5)
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6. A multipoint control unit for receiving compressed video signals from terminals in a conference and for transmitting selected compressed video signals to the terminals, the multipoint control unit comprising:
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a first bus having timeslots for transporting compressed video signals and audio signals; at least one bridge processor coupled to the first bus for placing compressed video signals and audio signals from respective terminals into timeslots of the first bus; a decoder for decoding compressed video signals received from timeslots of the first bus; a second bus receiving the decoded video signals at timeslots associated with respective terminals; selector means for selecting the decoded video signals from one or more timeslots of the second bus; and an encoder for encoding the selected decoded video signals and for applying the encoded video signals to the first bus; at least one bridge processor receiving the selected encoded video signals and audio signals from the first bus for transmission to the respective terminals. - View Dependent Claims (7, 8, 9)
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10. In a video teleconferencing system in which a plurality of audiovisual terminals operable to send and receive compressed digital video signals communicate with each other through a multipoint control unit having a video processing unit, the video processing unit comprising:
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a pixel bus having a plurality of timeslots for transporting uncompressed digital video signals; a pixel bus controller for controlling access to the pixel bus; and a plurality of processors, each processor coupled to the pixel bus and associated with at least one timeslot; each processor comprising; a decoder for decoding first compressed digital video signals from one of the plurality of audiovisual terminals to first uncompressed digital video signals; means for inserting the first uncompressed digital video signals into the at least one associated timeslot on the pixel bus when an output control signal is received from the pixel bus controller; means for receiving second uncompressed digital video signals from any timeslot associated with any processor when an input control signal is received from the pixel bus controller; a encoder for encoding the second uncompressed digital video signals to second compressed digital video signals; and means for transmitting the second compressed digital video signals to the one of the plurality of audiovisual terminals. - View Dependent Claims (11, 12)
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13. A video teleconferencing system comprising:
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a plurality of audiovisual terminals, each audiovisual terminal operable to send and receive compressed digital video signals; and a multipoint control unit for allowing the plurality of audiovisual terminals to communicate with each other in a conference, having a video processing unit, the video processing unit comprising; a plurality of processors, each processor comprising; a decoder for decoding first compressed digital video signals received from one of the plurality of audiovisual terminals to first uncompressed digital video signals; means for sending the first uncompressed digital video signals to any other processor; means for receiving second uncompressed digital video signals from any processor; an encoder for encoding the second uncompressed digital video signals to second compressed digital video signals; and means for transmitting the second compressed digital video signals to the one of the plurality of audiovisual terminals; wherein the decoder and the encoder comprise a coding algorithm, the coding algorithm for a respective processor matching a terminal coding algorithm for a respective audiovisual terminal and differing from the coding algorithms of other processors in the conference, such that the conference comprises audiovisual terminals having different terminal coding algorithms. - View Dependent Claims (14)
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15. In a multipoint control unit for receiving compressed video signals from terminals in a conference and for transmitting selected compressed video signals to the terminals, the method comprising the steps of:
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decoding the compressed video signals from respective terminals to uncompressed video signals; making the uncompressed video signals available at the respective maximum data rate of each uncompressed signal on a bus; selecting plural uncompressed video signals from the bus for a receiving terminal; and encoding the selected plural uncompressed video signals in a composite image for transmission to the receiving terminal at a data rate determined by the receiving terminal such that the receiving terminal receives each video signal in the composite image at maximum available image resolution.
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16. In a multipoint control unit for receiving compressed video signals from terminals in a conference and for transmitting selected compressed video signals to the terminals, the method comprising the steps of:
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decoding the compressed video signals from respective terminals to uncompressed video signals in a pixel domain; receiving the uncompressed video signals on a pixel bus having timeslots associated with respective terminals; selecting uncompressed video signals from one or more timeslots of the pixel bus; and encoding the selected uncompressed video signals for transmission to respective terminals. - View Dependent Claims (17, 18, 19, 20)
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Specification