Method and apparatus for caching, compressing and transmitting video signals

• US 20050105608A1
• Filed: 07/22/2004
• Published: 05/19/2005
• Est. Priority Date: 08/29/2002
• Status: Active Grant

• Current Assignee: Raritan Americas Incorporated (Legrand SA)
• Original Assignee: Raritan Americas Incorporated (Legrand SA)
• Inventors: Anderson, Swen, Coleman, Scott
• Granted Patent: US 7,606,314 B2
• Time in Patent Office: Days
• US Class Current: 375/240.10
• CPC Class Codes: G06F 12/0875 with dedicated cache, e.g. instruction or stack
• 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 2370/24 Keyboard-Video-Mouse [KVM] switch
• CPC Class Codes: H04N 19/137 Motion inside a coding unit, e.g. average field, frame or block difference
• CPC Class Codes: H04N 19/176 the region being a block, e.g. a macroblock
• CPC Class Codes: H04N 19/423 characterised by memory arrangements H04N19/433 takes precedence
• CPC Class Codes: H04N 19/507 using conditional replenishment
• CPC Class Codes: H04N 21/4143 embedded in a Personal Computer [PC]

Abstract

Disclosed is a method and apparatus for transmitting video signals from a remote computer to a local computer over a network such as a LAN, WAN, the Internet, etc. The method receives and digitizes signals from the remote computer, conditions the signals, and compresses the signals for efficient transmission over the network connection. The method and apparatus also utilizes a cache of recently transmitted video to further decrease the data needed for transmission of the signals. The conditioning and caching use frame buffers of video signals that are divided into cells to reduce noise in the image, and to limit the portions of the video signals that must be transmitted. The present invention maybe used in conjunction with a keyboard video mouse switch to enable a user at the local computer to select one of a number of remote devices for remote operation.

Claims

2. A method of transmitting video signals over a network from one of a plurality of remote computers to one of a plurality of user workstations, said method comprising the steps of:

receiving at least one video signal from a remote computer;

digitizing said video signal;

dividing said digitized video signal into one or more pixel blocks;

comparing each of said pixel blocks to a cache of stored pixel blocks using at least one code function;

transmitting to a user workstation said pixel blocks not in said cache; and

updating said cache with said transmitted pixel blocks.

3. A method according to claim 2, wherein said at least one code function generates at least one hash code for each said pixel block.

4. A method according to claim 2, wherein said at least one code function generates at least one cyclic redundancy check (CRC) code for each said pixel block.

5. A method according to claim 2, wherein said comparing uses at least a first and second hash code.

6. A method according to claim 2, wherein said comparing uses at least a first and second CRC code.

7. A method according to claim 2, wherein said comparing uses at least a hash code and a CRC code.

8. A method according to claim 2, wherein said comparing continues until a match indicative of a cache hit is found.

9. A method according to claim 8, wherein a reference code is transmitted to said user workstation upon said cache hit.

10. A method according to claim 2, wherein said comparing continues until comparison has been made to all of said stored pixel blocks in said cache.

11. A method according to claim 2, wherein said transmitting said pixel blocks not in said cache occurs upon no match of said pixel blocks to said stored pixel blocks in said cache.

12. A method of transmitting video signals over a network from one of a plurality of remote computers to one of a plurality of user workstations, said method comprising the steps of:

receiving at least one video signal from a remote computer;

digitizing said video signal;

dividing said digitized video signal into one or more pixel blocks;

computing at least a first and second hash code for each of said pixel blocks;

comparing said first and second hash codes to a cache of stored hash codes;

transmitting to a user workstation said pixel blocks not in said cache; and

updating said cache with said transmitted pixel blocks.

13. A method according to claim 12, wherein said comparing continues until a match indicative of a cache hit is found.

14. A method according to claim 13, wherein a reference code is transmitted to said user workstation upon said cache hit.

15. A method according to claim 12, wherein said comparing continues until comparison to all of said hash codes of said stored pixel blocks in said cache has occurred.

16. A method according to claim 12, wherein transmitting said pixel blocks not in said cache occurs upon no match of said first and second hash codes to said stored hash codes.

17. A keyboard, video, and mouse system for selectively controlling a plurality of remotely located computers from a plurality of local user workstations comprising:

at least one remote computer;

at least one user workstation;

a transformation apparatus for compressing, analyzing and converting at least one video signal from said remote computer;

a first and second frame buffer from said at least one remote computer; and

a cache of stored frame buffers;

wherein said transformation apparatus compares said first frame buffer to said second frame buffer by utilizing a first threshold and a second threshold stage; and

wherein said transformation apparatus divides said frame buffers into current blocks and compares said current blocks to said cache of stored frame buffers using a plurality of computed codes transmitting only those blocks not in said cache.

1. (canceled)

18. A system according to claim 17, wherein said computed codes are hash codes.

19. A system according to claim 17, wherein said computed codes are CRC codes.

20. A system according to claim 17, where said computed codes are a combination of hash codes and CRC codes.

21. A system according to claim 17, wherein said cache is updated upon said current blocks not being found in said cache.

20-1. A system according to claim 17, wherein a reference code is transmitted to said user workstation upon a match of said current blocks in said frame buffers to said cache of stored frame buffers.