Postprocessing Algorithm in Block-Coded Images Using the Adaptive Filters along the Pattern of Neighborhood Blocks

Suk-Hwan LEE  Seong-Geun KWON  Kee-Koo KWON  Byung-Ju KIM  Kuhn-Il LEE 

Publication
IEICE TRANSACTIONS on Information and Systems  Vol.E85-D  No.12  pp.1967-1974
Publication Date: 2002/12/01
Online ISSN: 
Print ISSN: 0916-8532
Type of Manuscript: LETTER
Category: Image Processing, Image Pattern Recognition
Keyword: 
postprocessing,  blocking artifact,  block-adaptive filtering, 

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Summary: 
A postprocessing algorithm is presented for blocking artifact reduction in block-coded images using the adaptive filters along the pattern of neighborhood blocks. Blocking artifacts appear as irregular high-frequency components at block boundaries, thereby reducing the noncorrelation between blocks due to the independent quantization process of each block. Accordingly, block-adaptive filtering is proposed to remove such components and enable similar frequency distributions within two neighborhood blocks and a high correlation between blocks. This type of filtering consists of inter-block filtering to remove blocking artifacts at the block boundaries and intra-block filtering to remove ringing noises within a block. First, each block is classified into one of seven classes based on the characteristics of the DCT coefficient and MV (motion vector) received in the decoder. Thereafter, adaptive intra-block filters, approximated to the normalized frequency distributions of each class, are applied adaptively according to the various patterns and frequency distributions of each block as well as the filtering directions in order to reduce the blocking artifacts. Finally, intra-block filtering is performed on those blocks classified as complex to reduce any ringing noise without blurring the edges. Experimental tests confirmed the effectiveness of the proposed algorithm.