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Optical Engineering

Predicting dc using ac coefficients for JPEG coding
Author(s): Gopal Lakhani
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Paper Abstract

The JPEG baseline algorithm codes the dc of a block by giving its difference with the dc of the previous block. We propose to use ac coefficients for this purpose. Our method computes the difference of the sum of pixels of two boundary columns (or rows), one belonging to the current block and the other to a previous block, and then manipulates it in the direct cosine transform (DCT) domain so that the average of the coded differences for the whole image is near zero. Experimental results show that our method reduces the average JPEG dc residual by about 75% for images compressed at the default quality level. The reduction is even higher for unquantized DCT blocks.

Paper Details

Date Published: 1 February 2008
PDF: 5 pages
Opt. Eng. 47(2) 027004 doi: 10.1117/1.2844508
Published in: Optical Engineering Volume 47, Issue 2
Show Author Affiliations
Gopal Lakhani, Texas Tech Univ. (United States)

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