1 February 2008 Predicting dc using ac coefficients for JPEG coding
Author Affiliations +
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.
© (2008) Society of Photo-Optical Instrumentation Engineers (SPIE)
Gopal Lakhani, Gopal Lakhani, } "Predicting dc using ac coefficients for JPEG coding," Optical Engineering 47(2), 027004 (1 February 2008). https://doi.org/10.1117/1.2844508 . Submission:


Image compression using conditioning contexts
Proceedings of SPIE (January 09 1997)
Index-compressed residual adaptive vector quantization
Proceedings of SPIE (July 05 1998)

Back to Top