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Digital watermark detection method and apparatus

  • US 7,471,807 B2
  • Filed: 03/25/2004
  • Issued: 12/30/2008
  • Est. Priority Date: 09/05/2003
  • Status: Expired due to Fees
First Claim
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1. A digital watermark detection apparatus to detect watermark information embedded in an input image signal, comprising:

  • an image-size-reduction unit configured to reduce an image size of the input image signal by reducing resolution of the input image signal and to generate a size-reduced image signal; and

    a detector to detect the watermark information in the size-reduced image signal, the detector including;

    a correlator to compute an auto-correlation function of the size-reduced image signal;

    an extraction unit configured to extract a specific frequency component signal by filtering the auto-correlation function; and

    an estimation unit configured to estimate the watermark information from the specific frequency component signal,wherein the correlator includes a controller which controls a phase of the size-reduced image signal to generate a phase-controlled image signal, the correlator computing, as the auto-correlation function, a correlation value between the phase-controlled image signal and the size-reduced image signal.

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