System for minimizing screen refresh time using selectable compression speeds

• US 6,505,239 B1
• Filed: 10/16/2000
• Issued: 01/07/2003
• Est. Priority Date: 11/14/1997
• Status: Expired due to Term

• Current Assignee: e-Parcel corporation
• Original Assignee: Atabok Japan Inc.
• Inventors: Kobata, Hiroshi, Gagne, Robert A. Jr., Tonchev, Theodore C.
• Primary Examiner(s): Dinh, Dung C.
• Application Number:
  US09/688,149
• Time in Patent Office: 813 Days
• Field of Search: 709/247, 709/231, 709/208, 709/233, 709/234, 709/232, 345/501, 345/2.1, 345/2.2, 345/2.3, 348/384.1, 348/387.1, 348/390.1, 348/397.1
• US Class Current: 709/208
• 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 2340/02 Handling of images in compressed format, e.g. JPEG, MPEG

Abstract

A system is provided for the remote control of one computer from another in which selectable compression speeds are utilized to minimize overall screen refresh time. In one embodiment, an algorithm selection module at one computer chooses the highest compression available corresponding to a worst case scenario, followed by measurement of the compression time and the transmission time, with the ratio of compression time to transmission time being used to select a decreased compression, thereby to lower compression time and consequently lower the overall screen refresh time. By adjusting both the send time and the compression time on the transmit side, the above ratio can be made to equal one, which corresponds to the most efficient utilization of the available bandwidth and CPU power, which in turn translates into the quickest screen refresh time for the remote control operation.

Claims

1. A system for minimizing the screen refresh time of a display in communication with a first computer over a network, said system comprising:

a compression algorithm selector on said first computer selecting one of several compression algorithms for compressing data at said first computer prior to transmission of said data over said network to said display, said compression algorithm selector comprising;

a calculator determining compression and transmission times of said data for more than one of said compression algorithms ; and

a selector selecting among said compression algorithms of said compression algorithms based on a relationship between the compression and transmission times determined by the calculator.

2. The system of claim 1, wherein said compression algorithms are ordered according to a compression rate that is defined between said compression time and said transmission time.

3. The system of claim 2, wherein compression algorithm selector iterativley evaluates several of said compression algorithms before said selector selects one of said compression algorithms.

4. The system of claim 3, wherein said display has a refresh cycle and wherein said compression algorithm selector iteratively selects from said plurality of compression algorithms for every refresh cycle.

5. The system of claim 1, wherein said display is divided into a plurality of grids and wherein said compression algorithm selector further comprises:

a check sum generator generating a check sum for each grid of said plurality of grids;

a comparator comparing the check sum of each grid to the previous check sum for said grid of said plurality of grids and detecting a change in check sum for each grid of said plurality of grids; and

a data compressor collecting and compressing data for each grid having a change in checksum, for each grid of said plurality of grids.

6. The system of claim 1, further comprising a variable transmitter capable of changing said transmission rate.

7. The system of claim 1, wherein said plurality of compression algorithms include run length encoding algorithms.

8. The system of claim 1, wherein the compression algorithm having the lowset compression rate comprises a run length encoding algorithm.

9. The system of claim 8, wherein the compression algorithm having the next higher compression rate comprises a Huffman compression algorithm preceded by run length encoding.

10. The system of claim 9, wherein the compression algorithm having the next higher compression rate includes a modified adaptive Huffman compression algorithm using a 9-bit tree entry size, said Huffman compression algorithm being preceded by run length encoding.

11. The system of claim 10, wherein said tree entry size is a 13-bit tree entry size corresponding to the highest compression rate.

12. The system of claim 1 wherein the predetermined value of the ratio is one.

13. A method for minimizing the screen refresh time of a display in communication with a first computer over a network, said method comprising:

selecting one of a plurality of a compression algorithms for compressing data at said first computer prior to transmission of said data over said network to said display;

determining the compression time and the transmission time of said data; and

selecting that compression algorithm of said plurality of compression algorithms based on a relationship between the compressions time and transmission time determined.