Method and apparatus for digitizing and compressing remote video signals

• US 7,684,483 B2
• Filed: 08/29/2002
• Issued: 03/23/2010
• Est. Priority Date: 08/29/2002
• Status: Active Grant

• Current Assignee: Raritan Americas Incorporated (Legrand SA)
• Original Assignee: Raritan Americas Incorporated (Legrand SA)
• Inventors: Coleman, Scott
• Primary Examiner(s): RAO, ANAND SHASHIKANT
• Application Number:
  US10/233,299
• Publication Number:
  US 20040042547A1
• Time in Patent Office: 2,763 Days
• Field of Search: 348142-160, 709202-220, 358420-539, 382160-170, 37524001-24029
• US Class Current: 375/240.01
• CPC Class Codes: H04N 19/507 using conditional replenishment
• CPC Class Codes: H04N 21/4143 embedded in a Personal Computer [PC]

Abstract

A method and apparatus for digitizing and compressing video signals for transmitting the signals between a remotely located computer and a host or local computer. The digitization and compression method and apparatus is capable of dividing frame buffers into cells and comparing image data from previously captured frame buffers to create synchronized video signals and transmit the video signals over an extended range by limiting the portions of the transmission bandwidth of pixel data transferred between the remote computer and the local computer. In an alternate embodiment of the present invention, a keyboard video mouse switch is disposed between the remotely located computer and the local computer.

Claims

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

receiving a video signal from a remote computer;

dividing said video signal into one or more blocks of pixels;

generating a histogram of pixel values for each of said blocks;

generating frequently occurring pixel values and infrequently occurring pixel values using said histogram;

determining if the infrequently occurring pixel values should be mapped to the frequently occurring pixel values;

converting said video signal to a compressed video signal by mapping said infrequently occurring pixel values to said frequently occurring pixel values based on said determining step, and;

transmitting said compressed video signal to a user workstation,

wherein said step of determining includes the steps of

calculating a distance function between a infrequently occurring pixel value and a frequently occurring pixel value;

comparing the computed distance function to a previously stored computed distance function;

replacing the previously stored computer distance function with the computed distance function if it is eater than the computed distance function;

repeating the steps of calculating, comparing and replacing distance functions for all frequently occurring pixel values against the infrequently occurring pixel value;

updating the color map if the stored distance function is less than a threshold distance;

repeating the step of repeating the steps of calculating, comparing and replacing distance functions for all frequently occurring pixel values against the infrequently occurring pixel value and updating the color map for all the infrequently occurring pixel values.

2. A method according to claim 1, wherein said video signal is digitized upon said receiving.

3. A method according to claim 1, said method further comprising a step of:

converting each pixel that comprises said video signal to a compact representation.

4. A method according to claim 3, wherein said compact representation is an 8-bit per pixel representation.

5. A method according to claim 1, wherein said converting includes mapping each said pixel according to a color code table.

6. A method according to claim 1, wherein said transmitting includes:

bit-splicing said video signal to form bit-frames;

compressing said bit-frames to form compressed bit-frames; and

sequentially transmitting said compressed bit-frames to said user workstation.

7. A method according to claim 6, wherein said compressing is preformed utilizing a lossless compression algorithm.

8. A method according to claim 1, said method further comprising the step of:

comparing one of said pixel blocks to a cache of stored pixel blocks.

9. A method according to claim 8, said method further comprising the step of:

updating said cache with one of said pixel blocks in response to said comparing.

10. A method according to claim 8, wherein said comparing includes computing a cyclic redundancy check (CRC) code for at least one of said pixel blocks.

11. A method according to claim 8, wherein said comparing includes computing at least one hash code for at least one of said pixel blocks.

12. A method according to claim 8, wherein said pixel blocks are only transmitted to said user workstation if said pixel blocks are not in said cache.

13. A method according to claim 1, wherein said remote computer and said user workstation are connected via a network.

14. A method according to claim 13, wherein said network is selected from the group consisting of a local area network (LAN), a wide area network (WAN), the Internet, a wireless network, or a modem connection.

15. A method according to claim 13, wherein said network further comprises a KVM switch.