Abstract: A video coding and transmission system may employ techniques for adapting buffered video to network condition changes. Video data may be coded as reference data and non-reference data. According to the embodiments, non-reference frame may be detected in buffered video while awaiting transmission to a network. When network degradation is detected, one or more of the buffered non-reference frames may be dropped when network degradation is detected. Information about the dropped frames may be passed to an encoder for updating buffer parameters for future encoding. In this manner, a video coding system may provide faster responses to changing network conditions than systems without such buffer management techniques.

Abstract: Some embodiments present a method of performing a variable shift operation. This method can be used by a microprocessor that does not allow variable shift operation for certain operand sizes. The method simulates a shift instruction that shifts an operand by a shift count. The method identifies a first shift command and a second shift command. The method computes a mask value. The mask value depends on whether the shift count is less than half of the operand size or greater than or equal to half of the operand size. The method uses the mask value to cause one of the first shift command and the second shift command to produce no shift. In some embodiments, the method allows for the shift count to be specified in bytes or in bits.

Abstract: Some embodiments provide an architecture for establishing a multi-participant conference. This architecture has one participant's computer in the conference act as a central content distributor for the conference. The central distributor receives data (e.g., video and/or audio streams) from the computer of each other participant, and distributes the received data to the computers of all participants. In some embodiments, the central distributor receives A/V data from the computers of the other participants. From such received data, the central distributor of some embodiments generates composite data (e.g., composite image data and/or composite audio data) that the central distributor distributes back to the participants. The central distributor in some embodiments can implement a heterogeneous audio/video conference. In such a conference, different participants can participate in the conference differently. For instance, different participants might use different audio or video codecs.

Abstract: A method, apparatus, system, and signal-bearing medium that in an embodiment determine at least one capability of a transfer of data, set at least one parameter that affects performance of the transfer to an initial state based on the capability, detect performance of the transfer, and modify the parameter based on the performance. In this way, the data transfer can adapt to changing capabilities of the network and the devices that send and receive the data.

Abstract: A video coding system and method for increasing a transmitted output bit rate of a video encoding system by altering the content of the bit stream. A video encoder may receive a coding mode signal from a computer application for coding source video data, the coding mode signal indicating a target bit rate having a risk factor related to transmission error associated to the target bit rate. The coded bitstream may be modified based on the risk factor indicated in the coding mode signal. A modified coded bitstream may be outputted at the target bit rate and at a reduced coding efficiency, and the channel may be tested for transmission errors. Based on the test results, a revised coding mode signal indicating the same target bit rate, but a revised risk factor may be provided. The coded bitstream may be revised by removing the modifications previously made to the coded bitstream and a revised coded bitstream having greater coding efficiency may be output at the target bit rate.

Abstract: Some embodiments provide an architecture for establishing a multi-participant conference. This architecture has one participant's computer in the conference act as a central content distributor for the conference. The central distributor receives data (e.g., video and/or audio streams) from the computer of each other participant, and distributes the received data to the computers of all participants. In some embodiments, the central distributor receives A/V data from the computers of the other participants. From such received data, the central distributor of some embodiments generates composite data (e.g., composite image data and/or composite audio data) that the central distributor distributes back to the participants. The central distributor in some embodiments can implement a heterogeneous audio/video conference. In such a conference, different participants can participate in the conference differently. For instance, different participants might use different audio or video codecs.

Abstract: Some embodiments provide an architecture for establishing a multi-participant conference. This architecture has one participant's computer in the conference act as a central content distributor for the conference. The central distributor receives data (e.g., video and/or audio streams) from the computer of each other participant, and distributes the received data to the computers of all participants. In some embodiments, the central distributor receives A/V data from the computers of the other participants. From such received data, the central distributor of some embodiments generates composite data (e.g., composite image data and/or composite audio data) that the central distributor distributes back to the participants.

Abstract: Some embodiments provide an architecture for establishing multi-participant audio conferences over a computer network. This architecture has a central distributor that receives audio signals from one or more participants. The central distributor mixes the received signals and transmits them back to participants. In some embodiments, the central distributor eliminates echo by removing each participant's audio signal from the mixed signal that the central distributor sends to the particular participant.

Abstract: Some embodiments provide an architecture for establishing a multi-participant conference. This architecture has one participant's computer in the conference act as a central content distributor for the conference. The central distributor receives data (e.g., video and/or audio streams) from the computer of each other participant, and distributes the received data to the computers of all participants. In some embodiments, the central distributor receives A/V data from the computers of the other participants. From such received data, the central distributor of some embodiments generates composite data (e.g., composite image data and/or composite audio data) that the central distributor distributes back to the participants.

Abstract: Some embodiments provide an architecture for establishing multi-participant audio conferences over a computer network. This architecture has a central distributor that receives audio signals from one or more participants. The central distributor mixes the received signals and transmits them back to participants. In some embodiments, the central distributor eliminates echo by removing each participant's audio signal from the mixed signal that the central distributor sends to the particular participant.

Abstract: Some embodiments provide an architecture for establishing multi-participant video conferences. This architecture has a central distributor that receives video images from two or more participants. From the received images, the central distributor generates composite images that the central distributor transmits back to the participants. Each composite image includes a set of sub images, where each sub image belongs to one participant. In some embodiments, the central distributor saves network bandwidth by removing each particular participant's image from the composite image that the central distributor sends to the particular participant. In some embodiments, images received from each participant are arranged in the composite in a non-interleaved manner. For instance, in some embodiments, the composite image includes at most one sub-image for each participant, and no two sub-images are interleaved.

Abstract: A method, apparatus, system, and signal-bearing medium that in an embodiment detect that a first packet is not received, add a place holder for the first packet in a buffer, request retransmission of the first packet, and create an estimated packet based on a combination of a second packet previous to the first packet, a third packet following the first packet, and a fourth packet from a previous frame that is spatially corresponding to the first packet. In another embodiment, a method, apparatus, system, and signal-bearing medium are provided that send a encoded packet to a receiver, save the encoded packet in a bitstream, determine whether the encoded packet is lost, and when the encoded packet is lost, decode the bitstream with the lost packet omitted and insert a reconstructed frame associated with the lost packet into a reference frame storage. In another embodiment, when the encoded packet is lost, a decoder is run on a reference frame chosen as the last uncorrupted frame.

Abstract: Some embodiments provide an architecture for establishing multi-participant video conferences. This architecture has a central distributor that receives video images from two or more participants. From the received images, the central distributor generates composite images that the central distributor transmits back to the participants. Each composite image includes a set of sub images, where each sub image belongs to one participant. In some embodiments, the central distributor saves network bandwidth by removing each particular participant's image from the composite image that the central distributor sends to the particular participant. In some embodiments, images received from each participant are arranged in the composite in a non-interleaved manner. For instance, in some embodiments, the composite image includes at most one sub-image for each participant, and no two sub-images are interleaved.

Abstract: Some embodiments provide an architecture for establishing multi-participant video conferences. This architecture has a central distributor that receives video images from two or more participants. From the received images, the central distributor generates composite images that the central distributor transmits back to the participants. Each composite image includes a set of sub images, where each sub image belongs to one participant. In some embodiments, the central distributor saves network bandwidth by removing each particular participant's image from the composite image that the central distributor sends to the particular participant. In some embodiments, images received from each participant are arranged in the composite in a non-interleaved manner. For instance, in some embodiments, the composite image includes at most one sub-image for each participant, and no two sub-images are interleaved.

Abstract: Some embodiments present a method of performing a variable shift operation. This method can be used by a microprocessor that does not allow variable shift operation for certain operand sizes. The method simulates a shift instruction that shifts an operand by a shift count. The method identifies a first shift command and a second shift command. The method computes a mask value. The mask value depends on whether the shift count is less than half of the operand size or greater than or equal to half of the operand size. The method uses the mask value to cause one of the first shift command and the second shift command to produce no shift. In some embodiments, the method allows for the shift count to be specified in bytes or in bits.

Abstract: Some embodiments provide an architecture for establishing multi-participant video conferences. This architecture has a central distributor that receives video images from two or more participants. From the received images, the central distributor generates composite images that the central distributor transmits back to the participants. Each composite image includes a set of sub images, where each sub image belongs to one participant. In some embodiments, the central distributor saves network bandwidth by removing each particular participant's image from the composite image that the central distributor sends to the particular participant. In some embodiments, images received from each participant are arranged in the composite in a non-interleaved manner. For instance, in some embodiments, the composite image includes at most one sub-image for each participant, and no two sub-images are interleaved.

Abstract: A step-wise approach to automatically determining the bandwidth of a communication channel includes dividing the channel's potential bandwidth into a number of ranges. An initial range is then selected and a series of data packets specific to the selected range are transmitted from a first endpoint to a second endpoint, with the second endpoint determining one or more channel metrics based on the transmitted packets (e.g., measured transmission rates). If the metrics indicate the current range accurately reflects the channel's bandwidth, a measured transmission rate of the transmitted data packets is used as the channel's bandwidth. Otherwise, another range is selected and the process is repeated. The described approach rapidly determines channel bandwidth, even when the channel between the two endpoints is asymmetric. Techniques described herein are particularly beneficial when used in conjunction with multimedia conferencing applications.

Abstract: A step-wise approach to automatically determining the bandwidth of a communication channel includes dividing the channel's potential bandwidth into a number of ranges. An initial range is then selected and a series of data packets specific to the selected range are transmitted from a first endpoint to a second endpoint, with the second endpoint determining one or more channel metrics based on the transmitted packets (e.g., measured transmission rates). If the metrics indicate the current range accurately reflects the channel's bandwidth, a measured transmission rate of the transmitted data packets is used as the channel's bandwidth. Otherwise, another range is selected and the process is repeated. The described approach rapidly determines channel bandwidth, even when the channel between the two endpoints is asymmetric. Techniques described herein are particularly beneficial when used in conjunction with multimedia conferencing applications.

Abstract: Some embodiments provide a method for adjusting a video sampling rate during an video encoding operation. The method receives a metric that quantifies the usage of a computer that performs the video encoding operation. The method computes an adjustment factor based on the metric. In some embodiments the metric is a system idle time. The method defines the video sampling rate based on the adjustment factor. Some embodiments compute the adjustment factor by performing a non-linear operation based on the metric. In some embodiments, the non-linear operation includes performing an integral operation based on the metric. In some embodiments, the non-linear operation includes performing a derivative operation based on the metric. Some embodiments perform more than one operation to compute the adjustment factor. In some embodiments, each operation is assigned a weight.

Abstract: Some embodiments present a method of performing a variable shift operation. This method can be used by a microprocessor that does not allow variable shift operation for certain operand sizes. The method simulates a shift instruction that shifts an operand by a shift count. The method identifies a first shift command and a second shift command. The method computes a mask value. The mask value depends on whether the shift count is less than half of the operand size or greater than or equal to half of the operand size. The method uses the mask value to cause one of the first shift command and the second shift command to produce no shift. In some embodiments, the method allows for the shift count to be specified in bytes or in bits.