Visually, I think AV1 adds less DCT-ish noise, but tends to blur small, low-contrast details a little more than x265. (Compare the ends of tree branches on the default image, Crepuscular Rays, or faraway tiles and details in Mercado dos Lavradores. Haven't done objective measurements though--you may disagree.) I, personally, like AV1's tradeoffs better, at least from what I see there. Patches of ringing draw attention, whereas slight blurring is something we're used to ignoring since it comes from lots of things besides codecs; natural vision and camera images aren't completely sharp either. (Dunno why AV1's that way, but might be that it does more aggressive deringing with that filter Monty's posting about next.)
The photo caption on the comparison in this story suggested the same conclusion re the detail vs. noise tradeoff, for what it's worth: https://www.cnet.com/news/google-mozilla-av1-photo-format-co...
The paper on the deringing filter included subjective tests, and it suggests that test subjects liked its results more consistently than you might guess from the changes in objective metrics--small sample size though: https://arxiv.org/pdf/1602.05975.pdf
Sometimes you may want x265's bias towards more detail; in the Tiger image, AV1 "cuts" the whiskers near the top of the image shorter than x265 does. Tricky to 'teach' encoders that some detail is more important than others despite both being equally low size or contrast.
Given they're both a ton better than JPEG, the big advantage to AV1 for a random developer is the openness; we can use it w/out needing to either take a legal risk or lean on the implementation of some company that's dealt with the HEVC patent mess for us.
Once I get past that, some of the test images look better on AV1, and some look better on x265. Some of them kill detail here, some of them kill detail there. I think this is a victory -- both of them perform really well, considering, and allocating a bit more bits to get it looking nice is always an option.
It's good to have a royalty-free codec that's actually good, and with much more profile and fanfare than just a weird garage-band secret project like VP9 was. And with widespread hardware support, it may actually make a dent in JPEG's marketshare.
[1] https://hn.algolia.com/?query=niftich%20fake%20sharpness&sor...
It's confusing how people seem to use HEIF to mean container. And if HEIF is actually the container, then what is the payload in Apple's case, and what exactly is HEIC?
HEIC is an ISOBMFF 'brand' to be used inside the container to indicate that the payload's codec is HEVC (in 'Main' profile or 'Main Still Picture' profile), and that it's one still-image and not a sequence [1].
In most of the cases where the payload is the HEVC codec, the corresponding file extension is encouraged to be .heic and the MIME-type follows as well. Apple has a note about this in their transcript at WWDC 2017 [3].
[1] https://nokiatech.github.io/heif/technical.html [2] https://mpeg.chiariglione.org/standards/mpeg-h/image-file-fo.... [3] https://developer.apple.com/videos/play/wwdc2017/513
HEIF is the Nokia-developed, MPEG and ISO-blessed container for image sequences and transforms, which is published as MPEG-H Part 12, and is based on the good-old ISOBMFF, which you typically recognize as the ".MP4 container". HEIF's most wide deployment right now is on Apple iPhones, where it's the new default capture format for still images and 'live' images (effectively, a short video on either side of a high-res still).
AV1 is the AOMedia-developed, Google/ex-On2/Xiph.Org/Cisco consensus video format that's the evolution of the VP8/VP9 line and Daala.
This format takes the nice royalty-free state-of-the-art MPEG container and puts a royalty-free payload in it, making it a useful best-of-both-worlds.