Enhancement of JPEG-Compressed Images by Re-application of JPEG
Journal of VLSI Signal Processing Systems - Special issue on multimedia signal processing
Deringing cartoons by image analogies
ACM Transactions on Graphics (TOG)
Effective blocking artifact reduction using classification of block boundary area
PCM'05 Proceedings of the 6th Pacific-Rim conference on Advances in Multimedia Information Processing - Volume Part II
A training-based method for reducing ringing artifact in BDCT-encoded images
EGMM'04 Proceedings of the Seventh Eurographics conference on Multimedia
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Blocking effects are a major degradation in block based image coding techniques. In this paper, we propose an adaptive postprocessor for the removal of blocking effects. The adaptation is achieved by changing filter coefficients according to the local characteristics of images and the blocking effects. Here, a space-variant lowpass filter is used to smooth the pixels at block boundaries where the blocking effects are highly visible. In addition, the pixels that are closed to an edge are adaptively regional or directional lowpass filtered if the blocking effects are obvious. As for the pixels at edges, they are left untouched by the postprocessor. Therefore, blocking effects can be removed without blurring the edge sharpness. Performance improvements compared with other techniques are obtained according to simulation results. The proposed postprocessor has 0-1 dB gain (depending on the images) compared with the loop filter of H.261, the linear filter, and the nonlinear space-variant postprocessor