Comment by janwas | Hacker News Reader

Comment by janwas | Hacker News Reader

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Ah, an accusation of misquoting. I actually quoted your exact words minus "is" and "it supports".

I think we disagree on the degree of flexibility, for sure.

A cap on layers (under user/browser) absolutely makes sense, but 4 at the format level is quite limiting, especially if you want to spend some of them on salient regions.

I agree that's possible, but not that it's efficient. You'd waste a few KiB on encoding skip blocks - AVIF layers represent the whole image, whereas JPEG XL can efficiently encode and update at group level.

How flexible did Jake find AVIF progressive in 2025? [1]

"it seems pretty limited. Only particular scaling values are allowed, and 1/8 is the smallest. Supposedly, additional layers are possible[..], but whenever I tried this, the encoder would error out, or explode the file size to ~400 kB, even at lowest quality. I guess that's why it's marked 'experimental'."

> Intermediate passes in AVIF can semantically be different from the final pass

Also true of JPEG XL - scans are additive.

[1]: https://jakearchibald.com/2025/present-and-future-of-progres...

I'm not sure if you're aware of this or not but juliobbv is the developer that fixed progressive AVIF, he is fully aware of how it works and how AV1 works in general.

"You'd waste a few KiB on encoding skip blocks" This tells me you don't know how codecs work... skip blocks are not expensive to code, they are very cheap.

Jake's blog post is outdated by the way, the progressive functionality is much more advanced than it was at that point in time because Julio worked on it.

> This tells me you don't know how codecs work

Laughable.

My conservative estimate is that a few-MP image with all but a smallish region encoded using skip blocks will spend a few KiB on that. This is very expensive compared to sending only a bounding box, hence it is unattractive for purposes of updating small regions with a whole-image layer.

I am glad to hear AVIF progressive has improved. But note that my original comment was: I find it misleading to call AVIF's "up to four passes" "very flexible". I believe that stands: contrasting the flexibility of (purpose-built) JPEG XL vs. the fairly strict limitations (inherited from video) of AVIF, I am astonished anyone would still call the latter "very flexible" by comparison.

Hi, I'm the author of the article you're quoting. AVIF was limited at the time of writing, but has since seen massive improvements, including progressive support.

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