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Adaptive transform coding by selecting optimum block lengths according to variatons between successive blocks

  • US 5,235,623 A
  • Filed: 11/14/1990
  • Issued: 08/10/1993
  • Est. Priority Date: 11/14/1989
  • Status: Expired due to Term
First Claim
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1. An adaptive transform coding method comprising:

  • a) storing subblocks of input digital samples representing an audio-frequency signal in a buffer at predetermined intervals, reading the stored samples from the buffer and segmenting the samples from the buffer into a plurality of blocks each having an integral multiple of length of said subblock;

    b) encoding each of said blocks into corresponding transform coefficients and storing said transform coefficients in a memory;

    c) squaring each of said transform coefficients;

    d) summing those of said squared transform coefficients which correspond to high-frequency components of said input digital samples to produce squared sums;

    e) detecting a minimum of said squared sums as corresponding to an optimum block length;

    g) selecting those of said transform coefficients which correspond to said optimum block length from said memory; and

    h) multiplexing the selected transform coefficients with a block length signal representative of said optimum block length.

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