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Method of reducing quantization noise generated during a decoding process of image data and device for decoding image data

  • US 5,949,908 A
  • Filed: 11/21/1995
  • Issued: 09/07/1999
  • Est. Priority Date: 11/24/1994
  • Status: Expired due to Term
First Claim
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1. A device for decoding coded image data divided into a plurality of blocks so as to generate decoded image data by applying an inverse orthogonal transformation to each block of said plurality of blocks, said device comprising:

  • a quantization-information detecting unit detecting block-quantization-step-size information indicative of quantization step sizes used for said plurality of blocks;

    a variable-gain-low-pass filter reducing high frequency components of said decoded image data located in a predetermined proximity of borders of said plurality of blocks based on said block-quantization-step-size information so as to take into account said quantization step sizes of a given block as well as differences in said quantization step sizes between said given block and adjacent blocks thereof, said high frequency components having frequencies higher than a predetermined frequency; and

    a control-signal generating unit generating a control signal by using said block-quantization-step-size information on a given block and adjacent blocks thereof, said control signal being indicative of said quantization step sizes used for said given block differences in said quantization step sizes between said given block and said adjacent blocks, and whereinsaid variable-gain-low-pass filter, operating based on said control signal, reduces said high frequency components in said given block by an increased amount as said quantization step sizes used for said given block increase in size, and reduces said high frequency components in said given block by an increased amount as said differences in said quantization step sizes increase.

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