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This could be what provides the 'activation energy' to get large Web sites working with JXL; it avoids the situation where you don't want to touch a new standar
by twotwotwo 7y ago
This could be what provides the 'activation energy' to get large Web sites working with JXL; it avoids the situation where you don't want to touch a new standard until everyone else switches too. If Google ships a decoder in Chromium, I would give JXL decent odds of getting a lasting niche.
Also, 20% off JPEG1 sizes is better than it may sound; you only save about 30% more by switching to any of the new codecs (JXL's VarDCT or the video-codec-based ones) that apply a ton of new tools. Given JPEG1 was published 1992, that just confirms to me Tim Terriberry's quip that it was "alien technology from the future."
Working against JPEG XL: it's four modern image formats in one (VarDCT, Brunsli, FUIF, and a separate lossless codec) so a ton of work to independently implement. Also, video codecs already have ecosystem support, and have or will probably get hardware support first.
Further out: "JPEG restoration" is something I mostly see experimental work about but could also take the old format a bit further. The idea is to use priors about what real images should look like to make an educated guess at the information that was quantized away, so you get less of the characteristic blocking and ringing from overcompresed images.
(For example, look at Knusperli, JXL's "edge-preserving filter", or AV1's CDEF. The "quantization constraint" supported by the first two of those is, to me, what makes it "restoration" and not just another loop filter: it can always return pixels that could have compressed to the exact DCT coefficients in the file.)
- JyrkiAlakuijala 7y agoThe separate lossless codec and FUIF and some additional ideas have been integrated into the modular mode. The modular mode and VarDCT can be mixed in the same image. JPEG XL decoder no longer performs 'quantization constraint', it is a classic loop filter, just with heuristics and control fields to maintain detail much better than loop filters in video codecs. If you start with sharp high quality originals that don't have yuv420 in them, you usually will see 65 % savings with JPEG XL, i.e. more than 30 % on top of brunsli. You can think of VarDCT-mode as guetzli(-35 %) + brunsli(-22 %) + format specific changes(-30 %) like variable sized dcts, better colorspace, adaptive quantization and loop filtering.
- twotwotwo 7y agoThanks, I appreciate the corrections and detail. I was mostly going by the committee draft on the arXiv (https://arxiv.org/abs/1908.03565 https://arxiv.org/abs/1908.03565 ), which still mentioned the quantization constraint (J.3) and a "mathematically lossless" mode (annex O) distinct from modular. "Four formats" was just imprecise wording on my part. The material already public about JPEG XL's design rationale, testing, and so on has been really fun to follow as an outsider. I selfishly hope there's more of it as the work on it and rollout continue. Even with the standard itself public, a lot can be mysterious to those not immersed in this stuff.
- janwas 7y agoYes, quantization constraint was removed post-CD and Annex O was recently merged into the modular mode to simplify the standard. JXL's page count is 1/2 to 1/3 of contemporary video codecs.
- twotwotwo 7y agoThanks. If there are places the public can follow progress post-CD, I'm curious. (I see https://gitlab.com/wg1/jpeg-xl/ https://gitlab.com/wg1/jpeg-xl/ was updated late Feb, yay.)
- janwas 7y ago:) There are updates every ~3 months at https://jpeg.org/news.html https://jpeg.org/news.html.