Video teleconferencing for networked workstations

Claims

We claim:

1. The video teleconferencing apparatus for a distributed data processing system having a plurality of computer workstations connected by a digital data network, the computer workstations comprising:

a) a master process executing on a processor of a local workstation formating and sending audio and video data across the digital data network as digital data packets to a remote workstation over a first variable bandwidth digital data connection;

b) a slave process executing on a processor of the remote workstation receiving and reconstructing the audio and video data from across the digital data network from the master process of the local workstation for audible and visual reproduction, respectively;

c) a master process executing on the processor of the remote workstation formatting and sending audio and video data across the digital data network as digital data packets to the local workstation over a second variable bandwidth digital data connection; and

d) a slave process executing on the processor of the local workstation receiving the audio and video data from across the digital data network from the master process of the remote workstation for audible and visual reproduction, respectively;

wherein the master process of the local workstation causes the execution of the slave process on the remote workstation to receive the audio and video data sent by the master process of the local workstation, the slave process of the remote workstation causes the execution of the master process on the remote workstation to send the audio and video data to the local workstation, and the master process of the remote workstation causes execution of the slave process on the local workstation to receive the audio and video data sent by the master process of the remote workstation.

2. The video teleconferencing apparatus of claim 1, wherein the local workstation executes a slave process for each master process executing on remote workstations and sending audio and video data to the local workstation.

3. The video teleconferencing apparatus of claim 1 wherein the master process of the local workstation comprises

a) audio transmission means for sending an audio data stream from the local workstation to the remote workstation via the digital data network such that the audio data can be reconstructed by the remote workstation into a continuous audio signal, and

b) video transmission means for sending video data from the local workstation to the remote workstation via the digital data network such that each frame of video data sent to the remote workstation is inserted into the audio data stream by the local workstation without affecting the continuity of the reconstructed audio signal at the remote workstation.

4. The video teleconferencing apparatus of claim 3 wherein

a) the video transmission means further comprises means for precluding a frame of video data from being sent to the remote workstation in response to a system overload condition; and

b) the audio transmission means further comprises means for sending the audio data stream corresponding to the precluded frame of video data to the remote workstation to prevent loss of continuity of the audio signal reconstructed by the remote workstation during a system overload condition.

5. The video teleconferencing apparatus of claim 4 wherein

a) the slave process of the remote workstation comprises acknowledgement transmission means for issuing a frame acknowledge message to the local workstation for each frame of video data successfully received from the local workstation by the remote workstation; and

b) the master process of the local workstation comprises acknowledgement receiver means for receiving the acknowledgement message from the remote workstation and for deferring the sending of another frame of video data from the local workstation to the remote workstation until an acknowledgement message for the most recently sent frame of video data is received from the remote workstation.

6. The video teleconferencing apparatus of claim 5 wherein the system overload condition is determined by the elapsed time between sending a frame of video data to the remote workstation and receiving an acknowledgement message for that frame of video data from the remote workstation.

7. The video teleconferencing apparatus of claim 6 wherein

a) the audio transmission means further comprises means for sending any audio data accumulated by the local workstation since the last video frame was sent to the remote workstation immediately upon receipt of the acknowledgement message from the remote workstation for the last video frame if an overload condition exists; and

b) the video transmission means further comprises means for sending the most recently available frame of video data from the local workstation to the remote workstation and dropping any other intervening frames of video data which became available during the elapsed time of the overload condition; and

c) the audio transmission means comprises means for sending to the remote workstation any audio data accumulated by the local workstation, since the last video frame was sent to the remote workstation, when another video frame becomes available at the local workstation for sending to the remote workstation if no overload condition exists; and

d) the video transmission means comprises means for sending the most recently available frame of video data from the local workstation to the remote w