Apparatus for synchronization and display of plurality of digital video data streams

• US 5,526,024 A
• Filed: 08/12/1994
• Issued: 06/11/1996
• Est. Priority Date: 03/12/1992
• Status: Expired due to Term

• Current Assignee: Avaya Incorporated
• Original Assignee: AT&T Corporation (AT&T, Inc.)
• Inventors: Katseff, Howard P., Gaglianello, Robert D.
• Primary Examiner(s): Hjerpe, Richard
• Assistant Examiner(s): WU, XIAO MIN
• Application Number:
  US08/289,987
• Time in Patent Office: 669 Days
• Field of Search: 345/1, 345/2, 345/3, 345/115, 345/118, 345/112, 345/185, 345/196, 345/197, 345/201, 345/198, 345/200, 348/564, 348/588, 395/153, 395/154
• US Class Current: 345/547
• CPC Class Codes: G06F 3/14 Digital output to display device ; Cooperation and interconnection of the display device with other functional units
• CPC Class Codes: G06F 3/1454 involving copying of the display data of a local workstation or window to a remote workstation or window so that an actual copy of the data is displayed simultaneously on two or more displays, e.g. teledisplay
• CPC Class Codes: G09G 2340/0435 Change or adaptation of the frame rate of the video stream
• CPC Class Codes: G09G 5/393 Arrangements for updating the contents of the bit-mapped memory

Abstract

Video image quality is preserved in an asynchronous network by providing a synchronizing arrangement in which the input of video data from an asynchronous network to a video data buffer is synchronized with the reading of information from the video data buffer. Synchronizing video data transfers to and from a video data buffer ensures that video data from only a single frame from a source is displayed on a display monitor at one time, thus maintaining image quality. Furthermore, multiple video data streams from several asynchronous sources can be displayed simultaneously on a single display screen using the synchronization technique. The synchronization arrangement synchronizes receipt of the different data streams into the frame buffer with the output of data from the frame buffer to the display screen.

Claims

1. Apparatus for displaying video data comprising:

means for asynchronously receiving the video data from an asynchronous network;

means for formatting a video display signal, that includes the video data, for display on a video display means, said formatting means including means for receiving the video data and outputting the formatted video display signal; and

means for synchronizing the receipt of the video data by the formatting means with the outputting of the formatted video display signal, said synchronizing means including means for positioning and clipping the video data prior to outputting the video data to the formatting means such that the video display signal includes video data from only a single frame at a time.

2. The apparatus of claim 1 wherein the formatting means simultaneously receives video data transmitted from a plurality of video sources.

3. The apparatus of claim 2 wherein the synchronizing means comprises:

means for storing video data received from the asynchronous network; and

means for outputting the video data from the storing means to the formatting means in response to a synchronizing signal from the formatting means.

4. The apparatus of claim 3 wherein:

the storing means includes means for indicating the locations in the storing means at which data are currently input and output; and

the outputting means includes means, responsive to the locations indicated by the indicating means, for retransmitting to the formatting means predetermined ones of the video data previously output from the storing means to the formatting means.

5. The apparatus of claim 3 wherein:

the storing means includes means for indicating the locations in the storing means at which data are currently input and output; and

the outputting means includes means, responsive to the locations indicated by the indicating means, for preventing predetermined ones of the video data in the storing means from being output from the storing means to the formatting means.

6. Apparatus for displaying video data comprising:

means for storing video data, said storing means asynchronously receiving the video data from an asynchronous network at a first, average information rate and outputting the video data at a second information rate;

means for formatting a video display signal that includes the video data for display on a video display means, the formatting means receiving video data output from the storing means and outputting the video display signal at a third information rate;

means for positioning and clipping the video data prior to receipt of the video data by the formatting means; and

means, responsive to a synchronization signal from the formatting means, for controlling the second information rate, such that the video display signal includes video data from only a single frame at a time.

7. The apparatus of claim 6 further comprising means for selectively retransmitting from the storing means to the formatting means predetermined ones of the video data previously output from the storing means to the formatting means if the third information rate exceeds the first information rate.

8. The apparatus of claim 6 further comprising means for selectively preventing predetermined ones of the video data from being output from the storing means if the first information rate exceeds the third information rate.

9. The apparatus of claim 6 wherein said storing means receives simultaneously the video data from a plurality of video sources.