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

• US 6,167,157 A
• Filed: 12/04/1998
• Issued: 12/26/2000
• Est. Priority Date: 11/24/1994
• Status: Expired due to Term

• Current Assignee: JVC Kenwood Corporation
• Original Assignee: Victor Company of Japan Limited (JVC Kenwood Corporation)
• Inventors: Sugahara, Takayuki
• Primary Examiner(s): Couso, Jose L.
• Application Number:
  US09/205,986
• Time in Patent Office: 753 Days
• Field of Search: 382/232, 382/233, 382/236, 382/238, 382/240, 382/248, 382/250, 358/432, 358/433, 348/384, 348/394, 348/395, 348/400-404, 348/407-416, 348/420-421, 348/425, 348/430, 348/431, 348/699
• US Class Current: 382/236
• CPC Class Codes: H04N 19/117 Filters, e.g. for pre-processing or post-processing sub-band filter banks H04N19/635
• CPC Class Codes: H04N 19/124 Quantisation
• CPC Class Codes: H04N 19/126 Details of normalisation or weighting functions, e.g. normalisation matrices or variable uniform quantisers
• CPC Class Codes: H04N 19/137 Motion inside a coding unit, e.g. average field, frame or block difference
• CPC Class Codes: H04N 19/139 Analysis of motion vectors, e.g. their magnitude, direction, variance or reliability
• CPC Class Codes: H04N 19/159 Prediction type, e.g. intra-frame, inter-frame or bidirectional frame prediction
• CPC Class Codes: H04N 19/176 the region being a block, e.g. a macroblock
• CPC Class Codes: H04N 19/46 Embedding additional information in the video signal during the compression process H04N19/517, H04N19/68, H04N19/70 take precedence
• CPC Class Codes: H04N 19/527 Global motion vector estimation
• CPC Class Codes: H04N 19/61 in combination with predictive coding
• CPC Class Codes: H04N 19/86 involving reduction of coding artifacts, e.g. of blockiness

Abstract

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 the plurality of blocks includes a quantization-information detecting unit detecting block-quantization-step-size information indicative of quantization step sizes used for the plurality of blocks. The device also includes a variable-gain-low-pass filter reducing high frequency components of the decoded image data in a predetermined proximity of borders of the plurality of blocks based on the block-quantization-step-size information, the high frequency components having frequencies higher than a predetermined frequency.

Claims

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 prediction-mode detecting unit detecting a prediction mode for said plurality of blocks, said prediction mode indicating one of an intra-frame coding mode and an inter-frame coding mode; and

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 prediction mode, said high frequency components having frequencies higher than a predetermined frequency wherein said variable-gain-low-pass filter comprises;

border determining means for determining whether a currently processed pixel is within said predetermined proximity of said borders;

low-frequency separating means for separating low frequency components of said decoded image data, said low frequency components having frequencies lower than said predetermined frequency;

high-frequency separating means for separating said high frequency components;

reducing means for reducing said high frequency components according to said prediction mode when said currently processed pixel is within said predetermined proximity of said borders; and

combining means for combining said low frequency components and an output of said reducing means.