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Acoustic signal transform coding method and decoding method having a high efficiency envelope flattening method therein

  • US 5,684,920 A
  • Filed: 03/13/1995
  • Issued: 11/04/1997
  • Est. Priority Date: 03/17/1994
  • Status: Expired due to Term
First Claim
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1. An acoustic signal transform coding method which transforms an input acoustic signal to frequency-domain coefficients and encodes them to produce coded output, said method comprising the steps of:

  • (a) obtaining residual coefficients having a flattened envelope of the frequency characteristics of said input acoustic signal on a frame-by-frame basis;

    (b) predicting the envelope of said residual coefficients of the current frame on the basis of said residual coefficients of the current or previous frame to produce a predicted residual-coefficients envelope;

    (c) normalizing said residual coefficients of the current frame by said predicted residual-coefficients envelope to produce fine structure coefficients; and

    (d) quantizing said fine structure coefficients and outputting index information representative of said quantized fine structure coefficients as part of said coded output.

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