Abstract: An echo canceller processing echo, noise and near end talk in a narrower, but still intelligible, frequency band for reducing required processing power and complexity. In a preferred embodiment of the present invention, an input audio signal of captured sound in an audio communication system is decimated and then divided into a number of sub bands by an analyze filter. Each sub band is processed as in background audio echo cancelling by subtracting the signal with an echo estimate from a model of the acoustic signal in the respective sub band, except from that the signal is also bypassed, adjusted by a filter and subtracted from the processed signal. The resulting signals are then recombined by a synthesize filter and interpolated to the original sampling rate and bandwidth. Finally, the output from the synthesize filter is added to the input audio signal, which has been delayed and adjusted by a filter.

Abstract: A system, apparatus, method, and computer program product for detecting and correcting packet losses that adversely affect video quality. This packet loss feature may be employed as part of the secure video conference system, method and computer program product, or be employed in a non-secure system, method and computer program product.

Abstract: A system, apparatus, method, and computer program product for establishing secure videoconferences between multiple nodes communicating via two or more transport protocols in which at least one encryption protocol is used.

Abstract: A method for prediction of the motion vector of a pixel block in a video picture that is to be coded. The actual motion vectors of two adjacent blocks close to the uppermost left corner of the block are selected as candidates for the prediction. One additional block, also adjacent to the block, is selected to decide which of the motion vectors to be used as the prediction. The vector difference to the motion vector of the decision block is decisive for the final selection.

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: The specification discloses a multimedia conferencing service capability for dynamically allocating transmission link bandwidth among video, audio and data channels in response to changes in the utilization of those channels. The capability maximizes video quality when data is not being used and minimizes data transfer time when data is being used in a multimedia conference. A multipoint control unit (MCU) monitors the utilization of T.120 MLP data channels and changes the bandwidth allocation for all of the transmission links in response to changes in the utilization for at least one of the data channels. The utilization is monitored by measuring the data rate of outbound T.120 MLP data channels and comparing the measured data rate to the allocated bandwidth to determine the data channel utilization.

Abstract: Continuous presence designed in accordance with H.261 recommendation allows for several sites to be seen simultaneously on one screen. For instance, the H.261 recommendation specifies that two picture scanning formats (i.e., CIF and QCIF) may be used in a codec. Notably, H.323 end-points could send pictures in QCIF while receiving CIF pictures. An MCU could select four appropriate sites, receive QCIF pictures from those sites, form a composite picture, and distribute the composite picture to the conferencing end-points. It is desired to be able to allow the sites to transmit pictures at different rates according to their preferences. Each site is associated with a queue into which the transmitted QCIF pictures are stored. The transmission rate for those sites are then deduced. A thread then activates to determine if there are QCIF pictures to be placed in the associated queues. Another thread retrieves the QCIF pictures from the queues based on the deduced transmission rate.

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.