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Adaptive transform coding using variable block size

  • US 5,241,395 A
  • Filed: 03/23/1992
  • Issued: 08/31/1993
  • Est. Priority Date: 08/07/1989
  • Status: Expired due to Term
First Claim
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1. A method for processing a signal corresponding to a still image so that said still image can be transmitted to a remote location via a channel, said method comprising the steps ofproviding a signal comprising a two-dimensional array of pixels which is representative of a still image,dividing said signal into blocks of pixels of size M×

  • M, each of said M×

    M blocks of pixels having a content,splitting each of said M×

    M blocks to produce a hierarchy of sub-blocks including the levels designated i-0,1,2, . . . ,K-1, so that at each level of the hierarchy, there are 4i sub-blocks of size M/2i ×

    M/2i, i=0,1, . . . ,K-1, where K is an integer,starting with the K-1 level in said hierarchy and proceeding to successive levels in said hierarchy, merging adjacent of said sub-blocks when the differences in the mean pixel value of said sub-blocks is below a predetermined threshold,applying an orthogonal transform individually to each of said sub-blocks comprising said M×

    M blocks of pixels to form transform coefficients for each of said sub-blocks,utilizing an encoder to convert the transform coefficients for each sub-block into a signal in the form of a stream of bits, andtransmitting said signal in the form of a stream of bits for each of said sub-blocks via a channel to a receiver at a remote location.

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