libjxl VS libavif

> Regarding JPEG XL's mobile support, it makes sense it would see limited development if the company that manages one of the biggest mobile players has been the greatest restriction on their success. The lack of support also disincentivises manufacturers to prioritise support.

There was literally no involvement from any hardware vendor in the standardization of JPEG XL. It went from a Call for Proposals in Sept 2018 to Committee Draft in Aug 2019 with very little time for industry feedback. Contrast this with AV1 which had involvement from hardware vendors Intel, NVIDIA, Arm, AMD, Broadcom, Amlogic from the beginning as well as companies who ship media on hardware at scale such as Cisco, Netflix, Samsung and yes Google. These companies reviewed and provided significant feedback on the format that made it suitable for hardware implementation.

https://news.ycombinator.com/threads?id=JyrkiAlakuijala is a lead on the project and a Google employee, and active in JPEG XL development https://github.com/libjxl/libjxl/commits?author=jyrkialakuij...

https://github.com/libjxl/libjxl/blob/main/doc/format_overvi... is a pretty detailed but good overview. The highlights are variable size DCT (up to 128x128), ANS entropy prediction, and chroma from luminance prediction. https://github.com/libjxl/libjxl/blob/main/doc/encode_effort... also gives a good breakdown of features by effort level.

For JPEG XL, refer to its format overview [1]. In short its lossless mode uses a combination of multiple techniques: the rANS coding with an alias table, LZ77, reversible color transforms, a general vector quantization that subsumes palettes, a modified Haar transform and a learnable meta-adaptive decision tree for context modelling.

One good thing about JPEG XL is that its lossy mode also largely uses the same tool, with a major addition of specialized quantization and context modelling for low- and high-frequenty components.

[1] https://github.com/libjxl/libjxl/blob/main/doc/format_overvi...

The cjxl source is here. If you spot any reason why -x strip=exif may not work, tell me.

The problem is that the instructions for actually running the WASM file are not that clear... the docs the author mentions shows how to compile to WASM, which is easy enough, but then here's the instructions to make that actually work in the browser:

https://github.com/libjxl/libjxl/blob/main/tools/wasm_demo/R...

Yeah, you need some mysterious Python script, a JS service worker at runtime, choose whether you want the WASM or WASM_SIMD target, use a browser that supports Threads and SIMD if you chose that, make sure to serve everything with the appropriate custom HTTP headers... just reading that, I can see that to get this stuff working on non-browser WASM targets would likely require expertise in WASM, which is the point of the OP. WASM's UX is just not there yet.

https://github.com/libjxl/libjxl#usage

> Specifically for JPEG files, the default cjxl behavior is to apply lossless recompression and the default djxl behavior is to reconstruct the original JPEG file (when the extension of the output file is .jpg).

I mean compiling a bleeding edge kicad, inkscape or jpeg-xl is easy. But will probably trash your system if you already have an older version installed.

But you look at your image viewer that could have the lossless indicator? (and there is an issue open to add this indicator to the jxl files)

https://github.com/libjxl/libjxl/issues/432

> Have you seen this more recent data that includes AVIF? https://cloudinary.com/labs/cid22

The graph from Cloudinary uses libaom to do the encoding at speed preset 7 (s7), which is far from speed preset 0 and disables many AVIF coding tools. I do not know why this was chosen by the author, but it does not reflect AVIF performance. According to https://github.com/AOMediaCodec/libavif/issues/440#issuecomm... speed preset 8 loses 20-35% compression efficiency.

It's 2023, surely this is not yet another bug related to memory unsafety that could be avoided if we'd stop writing critical code that deals with extremely complex untrusted input (media codecs) in memory unsafe languages?

Yep, of course it is: https://github.com/webmproject/libwebp/commit/902bc919033134...

I guess libwebp could be excused as it was started when there were no alternatives, but even for new projects today we're still committing the same mistake[1][2][3].

[1] -- https://code.videolan.org/videolan/dav1d

[2] -- https://github.com/AOMediaCodec/libavif

[3] -- https://github.com/AOMediaCodec/libiamf

Yep. Keep writing these in C; surely nothing will go wrong.

As far as I understand you are talking about this plugin. I don't know c++ and half of the code was like a black magic, but if I get it correctly, it encodes your images with libavif, and adds custom metadata ([solar/time of day] -> json -> base64).

So a few dozen comments, but so far it doesn't look like any mention the immediate thing that jumped out at me which was the claims vs AVIF:

>"In turn, what users will be given is yet another facet of the web that Google itself controls: the AVIF format."

Huh? I'll admit I haven't been following codecs as super ultra closely as I used to, but I thought AOM was a pretty broad coalition of varying interests and AV1 an open, royalty free codec that was plenty open source friendly? I've heard plenty of reasonable arguments that JPEG XL has some real technical advantages over AVIF and as well as superior performance is much more feature rich and scalable. So I could see people being bummed for that. But this is the first time I've heard the assertion that it's somehow a Google project? I mean, AOM's libavif reference is BSD too [0]? I'd love some more details on that from anyone who has been following this more closely. I can even understand if AOM isn't as community friendly and an accusation that it's dominated by big corps, but in that case why single out Google alone? From wiki:

>The governing members of the Alliance for Open Media are Amazon, Apple, ARM, Cisco, Facebook, Google, Huawei, Intel, Microsoft, Mozilla, Netflix, Nvidia, Samsung Electronics and Tencent.

Like, Google is certainly significant, but that's a lot of equally heavy hitters. And interesting that Mozilla is there too.

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0: https://github.com/AOMediaCodec/libavif

> You have a good point that AVIF layered image items can act like such P/B-frames. Do libavif (or other AVIF implementations if any) make use of them?

Seemingly. As search for "libavif progressive encoding" shows several issues about this, and a search for "progressive" in https://github.com/AOMediaCodec/libavif/blob/main/include/av... shows an enum for avifProgressiveState, appears to show support for it.

I mean, it already has it: https://github.com/AOMediaCodec/libavif/commit/570c42c2c10a878c8cc896f1c5daf1a955274142

Apart from mpv and ffplay, the only software I currently have installed that can play animated AVIF is Chromium. And from what I've read from this libavif bug report, I'm not sure if looping animated files in general is something that's just done by default by a lot of software regardless of whether the file is marked as a loop or not.

The support for progressive AVIF decoding has landed in libavif and in Chromium. But are there any docs on how to create and test progressive AVIF images?

The "for example" is the key here, because AVIF does support multi-layer coding per the spec now (though not currently implemented in libavif from what I can tell).