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Improved JPEG encoder.
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Image specific optimal thresholding strategy for the DCT coefficients #223

Open jrmsmith opened 8 years ago

jrmsmith commented 8 years ago

I would like to call your attention that this patented algorithm yielding the optimal thresholding strategy for the DCT coefficients [image specific] have expired:

https://patents.google.com/patent/US5734755A/en

The paper can be found here:

https://infoscience.epfl.ch/record/33889/files/RamchandranV94.pdf

This algorithm do not change the quantization tables, it only deals with finding the optimal thresholding strategy for the DCT coefficients. According to the authors, the algorithm affords a 12-15% reduction of image's size.

Best regards, John Smith.

kornelski commented 8 years ago

Thanks for the tip. The paper describes a technique that sounds quite similar to trellis quantization that mozjpeg already has.

@fbossen can you confirm?

jrmsmith commented 8 years ago

According to the authors [see patent], this algorithm provides the best thresholding strategy:

[The] threshold selection for the DCT coefficients of an image or video frame is based on optimizing for minimum distortion for a specified maximum target coding bit rate or, equivalently, for minimized coding bit rate for a specified maximum allowable distortion constraint.