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Deblocking of Block-Transform Compressed Images Using Weighted Sums of Symmetrically Aligned Pixels

Summary: Deblocking of Block-Transform Compressed Images Using
Weighted Sums of Symmetrically Aligned Pixels
A. Averbuch A. Schclar D. L. Donohoy
November 8, 2001
A new class of related algorithms for deblocking block-transform compressed images and
video sequences is proposed in this paper. The algorithms apply weighted sums on pixel quar-
tets, which are symmetrically aligned with respect to block boundaries. The basic weights,
which are aimed at very low bitrate images, are obtained from a 2-D function which obeys
prede ned constraints. Using these weights on images compressed at higher bitrates pro-
duces a deblocked image which contains blurred false edges near real edges. We refer to
this phenomenon as the ghosting e ect. In order to prevent its occurrences, the weights of
pixels, which belong to non-monotone areas, are modi ed by dividing each pixel's weight by
a prede ned factor called a grade. This scheme is referred to as weight adaptation by grad-
ing (WABG). Better deblocking of monotone areas is achieved by applying three iterations
of the WABG scheme on such areas followed by a fourth iteration which is applied on the
rest of the image. We refer to this scheme as deblocking frames of variable size (DFOVS).
DFOVS automatically adapts itself to the activity of each block. This new class of algorithms
produces very good subjective results and PSNR results which are competitive relative to
available state-of-the-art methods.


Source: Averbuch, Amir - School of Computer Science, Tel Aviv University


Collections: Computer Technologies and Information Sciences