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Proceedings Paper

Bayesian removal of coding block artifacts in the harmonic angular filter features domain
Author(s): Giovanni Jacovitti; Alessandro Neri
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Paper Abstract

Block based image and video coders operating in the DCT domain are affected by ringing, blurring and `blocking' artifacts due to quantization of DCT coefficients. At high compression ratios removal of blocking effects is required to improve service quality. For this purpose, a simple post-processing is suggested in the JPEG draft, while computationally expensive simulated annealing techniques are employed to account for the statistical behavior of actual images. In this contribution, a technique suggested by the criterion of separating the blocking artifacts from the image components in a `visual features space' is proposed. The visual feature space is obtained by filtering the decoded image with a `first order harmonic angular filter' (HAF) whose complex output represents the edges' strengths and orientations through its magnitude and phase. In this space both the image and the blocking artifacts are described by simple statistical models and blocking removal can then be performed by a proper non linear, zero memory, sub-optimal Bayesian estimator. Finally a restored image is reconstructed by the inverse of the HAF. After a brief introduction on the HAF feature space properties, the contribution provides a stochastic model of both the signal and the blocking patterns in the visual features space and the derivation of a corresponding sub-optimal `zero memory' Bayesian estimator. Computational aspects are addressed and performances are illustrated through classical examples for different levels of blocking artifacts on JPEG decoded images.

Paper Details

Date Published: 28 March 1995
PDF: 12 pages
Proc. SPIE 2424, Nonlinear Image Processing VI, (28 March 1995); doi: 10.1117/12.205214
Show Author Affiliations
Giovanni Jacovitti, Univ. of Rome La Sapienza (Italy)
Alessandro Neri, Univ. of Rome III (Italy)


Published in SPIE Proceedings Vol. 2424:
Nonlinear Image Processing VI
Edward R. Dougherty; Jaakko T. Astola; Harold G. Longbotham; Nasser M. Nasrabadi; Aggelos K. Katsaggelos, Editor(s)

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