Electrical computers and digital processing systems: multicomput – Computer conferencing
Reexamination Certificate
1997-02-12
2001-02-27
Peeso, Thomas R. (Department: 2767)
Electrical computers and digital processing systems: multicomput
Computer conferencing
C709S218000, C709S219000, C709S223000
Reexamination Certificate
active
06195683
ABSTRACT:
BACKGROUND OF THE INVENTION
Video communications has evolved over the years from a simple video telephone concept to a sophisticated network for allowing multiple users to participate in a video teleconference. For full featured video teleconferencing, users require both an audio communications path and a real time visual communication path synchronized to the audio path. Furthermore, it is desirable to support full color video and telephone quality audio. Video teleconferencing capabilities are limited mainly by the bandwidth of the transmission medium connecting the teleconferencing terminals.
Many computer workstations used in the office or laboratory environment today are connected with other workstations, file servers, or other resources over high-speed local area networks. Local area networks, in turn, are often connected together through high-speed gateways which connect workstations which may be distributed over a wide geographic area. Network wide protocols allow workstations to exchange packets of data at high rates of speed and reliability. Fixed bandwidth digital and analog video channels have been combined with computer networks to implement some video teleconferencing features. These include high bandwidth CATV/FDM type analog channels and fixed allocation TDM data channels for the video data.
SUMMARY OF THE INVENTION
Workstations today have obtained unprecedented computational power and utility. The powerful RISC type CPUs and fast, high resolution graphical displays have made possible multimedia workstations which integrate live audio and video into the programming environment. Graphical User Interface operating systems (GUI) have allowed effective integration of audio and video into application programming.
The present invention provides n-way video teleconferencing among networked computer workstations using the existing variable bandwidth digital data network for transferring synchronized audio and video teleconferencing data between the workstations. The teleconferencing apparatus and protocol of this invention provides high quality video teleconferencing without the need for a guaranteed wide bandwidth analog video channel or a fixed allocation digital video channel. Rather, the invention uses standard non-allocated data packets typically found on local area networks to transfer the audio and video teleconferencing data. Thus, no guaranteed bandwidth is required to carry on a useful video teleconference. An continuous audio data stream model provides continuous audio signals at the expense of video data when necessary, which is desirable since the ear is more sensitive to a break in the audio data than the eye is to the loss of a frame of video data. A “push” data model provides a secure system by preventing remote workstations from activating another workstation's video teleconferencing functions.
In general, in one aspect, the invention features a video teleconferencing method and apparatus for computer workstations connected by a digital data network. The computer workstations include a transmission source means for a local workstation to send audio and video teleconference data across the network to one or more remote workstations, and, a receiver for the local workstation to receive audio and video teleconference data back from the remote workstations. The local workstation sends teleconference data to each of the remote workstations over a variable bandwidth digital data connection, and each of the remote workstations returns teleconference data back to the local workstation over another variable bandwidth digital data connection. The variable bandwidth digital data connections include the data packet oriented data channels associated with, for example, FDDI, DECnet, and Ethernet local area networks. Furthermore, a wide area digital network, such as ISDN, can also be used with the video teleconferencing apparatus and method of this invention.
In preferred embodiments, the transmission source means includes a master software process executing on the local workstation, and the receiver includes a slave software process executing the remote workstation. The master software process formats and sends video teleconference data to the slave process. The slave process receives and reconstructs the audio and video teleconference data for audible and visual reproduction, respectively. The video data is presented as an image on the display of the receiving workstation, while the audio data is sent to either amplified speakers or headphones.
In other preferred embodiments, the master process of a local workstation causes execution of a slave process on a remote workstation for receiving video teleconference data from the local workstation. The slave process running on the remote workstation in turn causes execution of a master process on the remote workstation for sending video teleconference data back to the local workstation. The master process of the remote workstation in turn causes execution of a slave process on the local workstation for receiving the video teleconference data sent by the master process of the remote workstation. The local workstation executes a slave process for each master process on a remote workstation sending video teleconference data to the local workstation.
In yet other preferred embodiments, the transmission source includes an audio data transmitter for sending an audio data stream to the remote workstation such that the audio data can be reconstructed into a continuous audio signal. The transmission source also includes a video transmitter for sending video data to the remote workstation so that each frame of video data to be sent is inserted into the audio data stream without affecting the continuity of the reconstructed audio signal at the remote workstation.
In yet other preferred embodiments the video transmitter precludes a frame of video data from being sent to the remote workstation if a system overload exists. The audio transmitter sends the audio data stream corresponding to the precluded video frame to the remote workstation to prevent loss of continuity of the audio signal during a system overload. In other preferred embodiments the video transmitter precludes a frame of video data from being sent to the remote workstation in response to a system failure condition. The audio transmitter accumulates audio data for a predetermined time interval during the system failure condition, and transmits the accumulated audio data stream to the remote workstation once the failure has been corrected. For instance, the audio transmitter may continually accumulate the last ½ second of audio data while the failure exists, trimming any audio data older than ½ second. The last ½ second of audio data accumulated before the failure is corrected is sent to the remote workstation as soon as the failure is corrected. The most recently available frame of video is then also sent.
In still other preferred embodiments, timing information is attached to each frame of video data sent to the remote workstation. The timing information indicates a point in the continuous audio data stream which corresponds in time to the frame of video data. The receiver of the remote workstation includes a synchronizer for displaying a received frame of video when the point in the audio stream corresponding to the timing information of the received video frame is audibly reproduced at the remote workstation. The synchronizer counts the amount of audio data received in the continuous audio stream and compares the count to the timing information sent along with the most recently received video frame to determine when to display the frame.
In general, in another aspect, the invention features a multimedia computer workstation, such as a RISC workstation or IBM PC, having video teleconferencing capabilities. The multimedia workstation of this invention includes a network interface for establishing a variable bandwidth digital communications channel across a digital data network with another multimedia workstation. A video source provides a fra
Palmer Larry G.
Palmer Ricky S.
Compaq Computer Corporation
Hamilton Brook Smith & Reynolds P.C.
Peeso Thomas R.
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