Picturetel Corporation

Multilink Inc.

Qin-Fan Zhu

Louis J Kerofsky

A transmitting terminal transmits the data to a server and the server transmits the data to a receiving terminal. The server detects transmission errors in the data. If the server detects a transmission error, the server sends a request to the transmitting terminal for data correcting the effects of the detected transmission error on data affected by the detected transmission error. The server also sends the affected data to the receiving terminal prior to receiving the correction data. In other words, the server does not wait to receive the correction data before sending the affected data to the receiving terminal. Additionally, the server modifies the data received from the transmitting terminal to conceal the detected error from the receiving terminal.

Error correction and concealment during data transmission

A multipoint control unit (MCU) includes a plurality of segment processors arranged to extract segment data from a corresponding plurality of input video streams and a plurality of data queues, each one of the data queues being coupled to a corresponding one of the plurality of segment processors for storing segment data provided from the segment processors. The (MCU) also includes a data combiner coupled to the data queues for combining output data from the data queues and a controller coupled to the combiner for selectively providing data to the combiner in accordance with the amount of the data in the data queues. Several different approaches for determining what queues to obtain data from are described to reduce insertion delay Asymmetric picture rates are also used to reduce the video mixing delay. In addition, the multipoint control unit can optionally have the segment processors including a rate reducer and have the combiner controller send bit rate control information to the reducer to control the operation of the reducer.

Low delay real time digital video mixing for multipoint video conferencing

A transcoding method and apparatus having an input former, a requantizer, a buffer, a prediction processor, and a composite switch. The transcoder has multiple feedback paths routed through the composite switch that are selected depending upon system requirements. The input former can further include an inverse quantizer, a summer, and a selector. The selector connects different signal paths in the transcoder depending upon the coding mode of the input bitstream. The buffer can include a frame buffer, a QP buffer, and a comparator for generating a control signal. Further features of the transcoding method and apparatus include a frequency weighted thresholder and a computation resource manager.

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Wilmington, MA, United States of America

Qin-Fan Zhu