Do note that his "JPEG" is really JPEG with a PAQ entropy coder, which is actually a new format and not at all decodable by a JPEG decoder. He does no tests on baseline JPEG.

But it's useful to point out that a lot of new overly complex formats can't beat something as simple as that.

In my opinion, the biggest drawback of JPEG is that its window is non-overlapping. Ring-artifacts are generally not a big deal for natural images at medium quality or higher, but blocking artifacts can be noticeable even at relatively high quality settings.

There are a lot of post-processing techniques to try and mitigate this, but in my experience they tend to do about as much damage as they fix. The proper solution is to overlap the blocks using one of the myriad techniques DCT-based audio codecs use.

It is bizarre to me that for all of the attempts to beat JPEG, nobody seems to have tried simply overlapping the blocks by 2 pixels. You'd have an implementation only marginally more complex than JPEG (in fact, you can even implement it on top of an existing JPEG encoder/decoder) with a slowdown of only 25%.

JPEG-XR has (optional) lapping. But lapping has the problem that you can't do spatial intra prediction, which is significantly more valuable. And no one figured out how to make frequency-domain intra prediction as good until Daala. Plus deblocking filters have gotten pretty good now that they're tuned based on the quantizer used.

But a bigger problem is that no one is really interested in designing a new still image codec that's better than JPEG, since JPEG can't be unseated. So video codecs are where the practical development goes. And avoiding in-loop deblocking filters there means OBMC, which is extremely computationally intensive.

We'd likely have moved on to jpeg2k if it weren't for the patents.

(*)Charles Bloom.

Fixed.