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Video telecommunication system and method for compressing and decompressing digital color video data

  • US 4,847,677 A
  • Filed: 04/27/1988
  • Issued: 07/11/1989
  • Est. Priority Date: 04/27/1988
  • Status: Expired due to Term
First Claim
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1. A method for compressing digital color video data in a video telecommunication system having means for generating a color video signal for a plurality of video picture frames, with each picture frame comprising a plurality of scan lines composed of a plurality of pixels, and each pixel in said picture frame comprising three digital color components, said method comprising the steps of:

  • (a) determining a luminance function for each pixel based upon at least one of said three digital color components;

    (b) determining at least one decision parameter for at least a substantial portion of the pixels in the scan lines of a current picture frame based upon the difference of said luminance function between pixels a predetermined distance from at least one other pixel on each scan line;

    (c) comparing said at least one decision parameter with a corresponding threshold value to determine starting pixels and ending pixels for run lengths of sequentially related pixels in said scan lines, said run lengths being of a first digital word size, and said three color components being of second, third, and fourth digital word sizes, respectively;

    (d) encoding all of said digital color components in said picture frame according to a look up table of digitally compressed color codes of the most visually significant color combinations of a fifth digital word size smaller than the sum of said second, third and fourth digital word sizes;

    (e) encoding a plurality of combination of said run lengths and digitally compressed color codes representing at least a portion of said picture frame;

    (f) comparing said run lengths and digitally compressed color codes of said current picture frame with the run lengths and digitally compressed color codes of a previous picture frame to determine changes from said previous picture frame to said current frame; and

    (g) encoding said changes from said previous picture frame to said current picture frame for at least a portion of said picture frames, whereby once an initial picture frame is encoded, only those changes in subsequent picture frames are encoded.

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