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Reposted by Gianni Rosato

WebPerformance Report @webperfreport.bsky.social · 20/09/2026

⚡Featured posts this week: ✨ New ad metrics in CrUX: @alextcone.bsky.social ✨ The case against JPEG XL: @giannirosato.com ✨ Why Spotify Is Not Using Bayesian A/B Testing: Mattias Frånberg, Mårten Schultzberg ✨ International SEO: @polemicdigital.com 🙏 Special thanks to the authors! #webperf

WebPerformance Report performance email preview highlighting optimization scores, Perf Links, and Core Web Vitals metrics on a colorful gradient background.

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Joan León @nucliweb.net · 20/09/2026

The case against JPEG XL Investigating JPEG XL's place as a Web image codec, by @giannirosato.com, via @webperfreport.bsky.social giannirosato.com/blog/post/ca... #JPEGXL #JXL #ImagePerf #WebPerf

A dark-themed line chart titled “SSIMULACRA2,” showing BD-Rate (%) versus encoding speed in milliseconds for several image codecs. Colored lines compare codecs including AOM, JPEG XL, aperture-alpha, Iris-WebP, libjxl, SVT-AV1, and libwebp, with labeled data points. Most curves show higher BD-Rate at slower speeds, while some reach negative BD-Rate at faster speeds.

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Jake Archibald @jakearchibald.com · 14/09/2026

This is a great article. I've always been sus about the hype around JPEG XL, as it never stacked up when I actually tested it with web use-cases. giannirosato.com/blog/post/ca...

giannirosato.com

The case against JPEG XL | Gianni Rosato

Investigating JPEG XL's place as a Web image codec.

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Gianni Rosato @giannirosato.com · 14/09/2026

Might be one of my more controversial posts: "The case against JPEG XL" Link: giannirosato.com/blog/post/ca... 🫡 #compression #jpegxl #av1

giannirosato.com

The case against JPEG XL | Gianni Rosato

Investigating JPEG XL's place as a Web image codec.

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Gianni Rosato @giannirosato.com · 07/09/2026

New Halide blog post on some of the weaknesses of perceptual metrics: halide.cx/blog/metric-... These lessons are helping us develop our next encoder, Aperture. #compression

lnkd.in

This link will take you to a page that’s not on LinkedIn

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Jake Archibald @jakearchibald.com · 25/08/2026

It's really weird that the response to JPEG XL shipping is "yesss fuck WebP!" Like, we've had AVIF for years, and it outperforms JPEG XL in almost all web use-cases.

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Gianni Rosato @giannirosato.com · 10/07/2026

Hey everyone! fmetrics, a fast open-source perceptual metrics toolkit that runs on the CPU, is here: github.com/halidecx/fme... fmetrics supports IW-SSIM, MS-SSIM, CVVDP, SSIMULACRA2, & Butteraugli. See the blog post (halide.cx/blog/fmetrics) for more info. All code is Apache 2.0. Enjoy!

github.com

GitHub - halidecx/fmetrics: Fast image & video fidelity metrics in C, Zig

Fast image & video fidelity metrics in C, Zig. Contribute to halidecx/fmetrics development by creating an account on GitHub.

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Rachel Barker @rachelplusplus.me.uk · 12/06/2026

I've been improving my image compression project on and off for the last six months or so. Today I got it to basically where I want it feature-wise, so I've put out an alpha release and written a quick little blog post about it: www.rachelplusplus.me.uk/blog/2026/06...

rachelplusplus.me.uk

Tinyavif v2.0 alpha - Rachel++

I've put out a preview of the next version of tinyavif. It's basically feature-complete to what I want v2.0 to be, and I've run some quick correctness tests, so it's ready for experimental use.

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Gianni Rosato @giannirosato.com · 28/05/2026

The Codec Wiki has moved from wiki.x266.mov to codecs.wiki – apologies for the down-time!

wiki.x266.mov

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Gianni Rosato @giannirosato.com · 12/03/2026

fcvvdp 0.2.0! github.com/halidecx/fcv... Highlights: ~9-12% speed boost for single-threaded, task threading (220% faster than the reference implementation with 8 threads on my 13700k), FFmpeg support via patch. Check it out and lmk what you think!

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Ignacio Castano @icastano.bsky.social · 10/02/2026

I've put together an updated version of the Sponza scene with uncompressed PNG and compressed AVIF textures. I wrote about the process and compared the results against KTX. www.ludicon.com/castano/blog... #webgpu #web3d #sparkjs

ludicon.com

An Updated Sponza glTF – Ignacio Castaño

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Gianni Rosato @giannirosato.com · 05/02/2026

New Halide blog post on post-processing for chroma as it is relevant to compression efficiency: halide.cx/blog/chroma-... Seems like you can get a roughly 2% efficiency improvement with 4:2:0 decoder output just with smarter post-processing for chroma. Pretty neat! #avif #webp #jpeg

halide.cx

Same Image, Different Score? | Halide Compression

Metrics don't just measure encoder performance; decoding matters too, and even after decoding, not all post-processing is created equal.

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damarberlari.bsky.social @damarberlari.bsky.social · 22/01/2026

the 2nd part of my dithering visual article is finally out! 🔗 visualrambling.space/dithering-pa... this one mainly explores the threshold map and how it generates those unique visual patterns hope you enjoy this as much as I enjoyed making it! made with #threejs & #animejs

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Gianni Rosato @giannirosato.com · 24/01/2026

SVT-AV1 4.0.0 is here! Changelog: gitlab.com/AOMediaCodec... SVT-AV1-PSY's porting efforts are fully complete, and this release also features huge AVIF improvements. Maybe the most exciting release to date by my standards – SVT-AV1 is finally a real perceptual encoder! #av1 #avif #compression

gitlab.com

v4.0.0 · Alliance for Open Media / SVT-AV1 · GitLab

[4.0.0] - 2026-1-23 API updates Major release with...

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Gianni Rosato @giannirosato.com · 24/12/2025

Happy Holidays! Introducing fcvvdp, a faster CVVDP implementation: github.com/halidecx/fcv... Compared to the reference implementation running on the CPU, fcvvdp is faster (~15%) despite being single-threaded. It sees stronger wins with user time (up to ~15x) and memory usage (>90% less memory).

github.com

GitHub - halidecx/fcvvdp: Fast CVVDP implementation in C

Fast CVVDP implementation in C. Contribute to halidecx/fcvvdp development by creating an account on GitHub.

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Julio Barba @juliobbv.bsky.social · 05/12/2025

SVT-AV1-HDR 3.1.3 "Cyclonus" is out! Including all-new features from SVT-AV1, plus code cleanups and stability fixes. Get the newest version of this all-purpose AV1 video encoder! ffmpeg and HandBrake builds are available by clicking the link below: github.com/juliobbv-p/s...

github.com

GitHub - juliobbv-p/svt-av1-hdr: An all-purpose AV1 video encoder designed for visually-optimal SDR and HDR image and video encoding.

An all-purpose AV1 video encoder designed for visually-optimal SDR and HDR image and video encoding. - juliobbv-p/svt-av1-hdr

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Gianni Rosato @giannirosato.com · 04/11/2025

I spoke with @juliobbv.bsky.social at VideoLAN Dev Days in London! Here are our slides, discussing SVT-AV1-PSY: giannirosato.com/files/svt-av... I'll find access to the video & post it soon!

giannirosato.com

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Gianni Rosato @giannirosato.com · 12/10/2025

Introducing oavif: faster target quality image compression giannirosato.com/blog/post/oa... oavif can be up to 63% faster than traditional target quality encoders. Learn how in the attached blog post! #av1 #avif #compression

giannirosato.com

Introducing oavif | Gianni Rosato

oavif is a new approach to target quality encoding in image compression, designed around smarter convergence strategies and quicker scoring to be as fast as possible.

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Gianni Rosato @giannirosato.com · 03/10/2025

fssimu2 has its first release! github.com/gianni-rosat... fssimu2 is a fast SSIMULACRA2 implementation in Zig, with support for distortion map output. It is ~23% faster than the reference implementation at ~40% less memory usage, while being 99.97% accurate. Give it a look if you're interested!

github.com

Release 0.1.0 · gianni-rosato/fssimu2

First release! 🎉 Check README for more information. What's Changed generate LUT at compile time by @damster101 in #1 Zig 0.15.1 by @gianni-rosato in #3 feat: remove all simd in favor of scalar imp...

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Gianni Rosato @giannirosato.com · 15/09/2025

New Halide blog post! halide.cx/blog/consist... Quality and speed define an image encoder's compression performance. Consistency is a close third, and easily overlooked in image encoder design. What value does it provide, and how can we measure it? #avif #webp #jxl #jpegxl #compression

halide.cx

Measuring Image Encoder Consistency | Halide Compression

Quality and speed define an image encoder's compression performance. Consistency is a close third, and easily overlooked in image encoder design. What value does it provide, and how can we measure it?

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Ignacio Castano @icastano.bsky.social · 09/09/2025

New blog post about my experiences using spark.js with three.js: www.ludicon.com/castano/blog... Re-posts and feedback appreciated!

ludicon.com

three.js + spark.js – Ignacio Castaño

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Gianni Rosato @giannirosato.com · 30/08/2025

Anyone using rss/atom readers can now type `giannirosato.com` into their reader to get my website's atom feed

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Gianni Rosato @giannirosato.com · 29/08/2025

I got to interview Julio Barba from Google for the Halide blog: halide.cx/blog/julio-b... Go check it out if you're interested in what the next decade of multimedia tech might look like!

halide.cx

An Interview With Julio Barba | Halide Blog

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Gianni Rosato @giannirosato.com · 29/08/2025

Completely redesigned my website with Zola (www.getzola.org) – check it out at giannirosato.com Let me know if any links are broken if you link to my site – it should be fully backwards compatible with my old link hierarchy

getzola.org

Zola

Everything you need to make a static site engine in one binary.

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Luc Trudeau @luctrudeau.bsky.social · 01/08/2025

The “AV1 is a disaster” myth Here’s what’s actually true: - SVT-AV1 is fast, fully multithreaded and packed with SIMD. - It scales beautifully on modern CPUs. - It beats x264, x265, and VP9 in bitrate vs runtime. AV1 on CPU isn’t a disaster. It’s quietly winning.

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Gianni Rosato @giannirosato.com · 22/08/2025

Tune 3: Still Picture is coming to SVT-AV1: gitlab.com/AOMediaCodec/SVT-AV1/-/m… Formerly Tune 4 in SVT-AV1-PSY. Thank you @juliobbv.bsky.social !

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Gianni Rosato @giannirosato.com · 30/07/2025

Exciting #avif news – libaom’s tune iq (derived from SVT-AV1-PSY’s Tune 4) is used across The Guardian’s website now. They say they serve mostly AVIF, with JPEG XL shipped when supported. Very exciting stuff! Thanks @juliobbv.bsky.social!

“[sorry for the spam] Just wanted to say that theguardian.com is on `tune=iq` for the last two weeks (we serve AVIF to non-JXL-supporting browsers) and we couldn’t be more happy. Encoder consistency is much, much higher (still not as good as JXL, but that’s just an impression, not a rigorous assessment): some highly compressible images where delicate detail was being obliterated grown even ~3× in filesize and look much better while unnecessarily weighty images shrank, mostly without any perceptible degradation. Interestingly, we kept the same quality values (which differ by dpr) and as much as we can say, the overall bandwidth stayed more or less the same (I can’t see any change in the graph), so it’s likely the massive reduction of rare weighty images offset small images growing.

Huge thanks to juliobbv for his work on `tune=iq` and to whomever else worked on it. And to friends at our image CDN (Fastly). And to everyone here as without this server, I wouldn’t even know about it…
As always, we welcome improvements to any and all encoders. So the idea of “splitting Julio” couldn’t sound more exciting 😉.”

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Rachel Barker @rachelplusplus.me.uk · 19/07/2025

New post! After my previous post about image compression, a few people asked me to try different encoder settings. So I went ahead and tested a couple of them :) www.rachelplusplus.me.uk/blog/2025/07...

rachelplusplus.me.uk

A Better Image Compression Comparison - Rachel++

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Gianni Rosato @giannirosato.com · 14/07/2025

Improving AVIF in Open Source via the Halide blog halide.cx/blog/improvi... I wanted to write this to explain some of what went into Tune 4/Tune IQ, & help outline some of my reasoning for starting Halide Compression in the first place. I hope you enjoy! #av1 #avif #encoding

halide.cx

Improving AVIF in Open Source | Halide Blog

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Gianni Rosato @giannirosato.com · 09/07/2025

Introducing Iris-WebP, a better WebP encoder: halide.cx/iris/index.h... Iris offers up to >20% better compression than libwebp, and trades blows with libaom for AVIF. My goal is to build an image-first encoder ecosystem for the modern Web, so that new web image codecs aren't generally superfluous.

Iris-WebP BD-rate performance, showing speed-to-quality efficiency roughly on par with standard libaom.

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The New York Times @nytimes.com · 19/06/2025

The world’s largest digital camera — which will create an unparalleled map of the night sky — is at the heart of the new Vera C. Rubin Observatory in Chile. Here’s how it works. nyti.ms/4n8OpgP

The Vera C. Rubin Observatory, a large white and brown building, sits atop a mountain at sunset with an orange and pink sky. A headline reads: "Earth's Largest Camera Takes 3 Billion-Pixel Images of the Night Sky." Photo by Marcos Zegers for The New York Times

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Gianni Rosato @giannirosato.com · 17/06/2025

"I designed my own ridiculously fast game streaming video codec – PyroWave" themaister.net/blog/2025/06... Cool to see github.com/psy-ex/metrics in use in the wild, I'm glad it was useful!

themaister.net

I designed my own ridiculously fast game streaming video codec – PyroWave – Maister's Graphics Adventures

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Rachel Barker @rachelplusplus.me.uk · 13/06/2025

New blog post: I've spent the last couple of months building a tool to compare different image encoders, and wrote an article about some of the things you need to consider to get reliable results. I also talk a bit about how JPEG-XL is looking promising! www.rachelplusplus.me.uk/blog/2025/06...

rachelplusplus.me.uk

Evaluating image compression tools - Rachel++

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Gianni Rosato @giannirosato.com · 10/06/2025

Help restore the tax deduction for software dev in the US (Section 174) news.ycombinator.com/item?id=4422... If you live in the US and you've ever used a piece of software, you're probably interested in this. There's a sign-able letter attached.

news.ycombinator.com

Tell HN: Help restore the tax deduction for software dev in the US (Section 174) | Hacker News

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Rachel Barker @rachelplusplus.me.uk · 26/05/2025

May have bitten off quite a lot with this next blog post, but the goal is in sight! Basically built an encoder comparison tool from scratch, to really nail down the details in my own mind. Should have some interesting things to say soon - think of it as a "yes, and" to Gianni's excellent post:

giannirosato.com

Comparing Video Encoders

Comparing video encoders is easy, but not often done correctly.

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Rachel Barker @rachelplusplus.me.uk · 21/05/2025

Lil' teaser for an upcoming blog post, building on my last post (www.rachelplusplus.me.uk/blog/2025/03...): This graph compares compressing an image at a single fixed resolution (dotted curve) vs. encoding at multiple resolutions, netflix style (solid curve):

A graph comparing the size of a compressed image file against the image quality. There are three pairs of curves, comparing libaom version 3.12.1, jpegli 0.11.1, and tinyavif 1.1. Each pair has one solid curve and one dotted curve, with the dotted curve representing the size vs. quality tradeoff for encoding at a single size, and the solid curve representing netflix-style multi-resolution encoding.

The curve for libaom is the leftmost, and the curves for jpegli and tinyavif cross over as each one does better at different quality ranges. The curves for multi-resolution encoding break away from the single-resolution curves and go further to the left at lower qualities, representing better compression due to switching to a smaller resolution.

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Jon Sneyers @sneyers.info · 19/04/2025

'Spilling and smearing' 2025, Jon Sneyers, image/jxl, 31 bytes #jxlart jxl-art.lucaversari.it?zcode=c8osSU...

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Gianni Rosato @giannirosato.com · 14/04/2025

Very good article explaining entropy from an information theory perspective – highly recommend reading if you’re interested: jasonfantl.com/posts/What-is-Entropy

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Gianni Rosato @giannirosato.com · 08/04/2025

Updated numbers for Eve-AV1 & Eve-VP9 are public! The last time they were updated was around 2019, so this should give a more relevant look at how they perform. It takes a lot to improve a mature video encoder, and I'm very impressed with the Eve lineup. Shout-out @luctrudeau.bsky.social! #av1

Eve-VP9 versus open-source alternatives (libvpx, x264, x265) showing impressive gains.

Eve-AV1 versus open-source alternatives (SVT-AV1, libaom) showing impressive gains.

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Luc Trudeau @luctrudeau.bsky.social · 26/03/2025

The real headline isn’t #HDR10+. It’s that #AV1 is about to become the most streamed codec at #Netflix "AV1-SDR is already the second most streamed codec at Netflix, behind H.264 [...] we expect the day is not far when AV1 will be the most streamed codec at Netflix" Quiet shift. Big milestone.

netflixtechblog.com

HDR10+ Now Streaming on Netflix

Roger Quero, Liwei Guo, Jeff Watts, Joseph McCormick, Agata Opalach, Anush Moorthy

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UHD4k 📺 @uhd4k.bsky.social · 25/03/2025

In addition to HDR10 and Dolby Vision, Netflix now also streams content in HDR10+ format, encoded in AV1, on compatible devices. It appears that Netflix has been waiting to adopt AV1 beyond SDR until it could do so with HDR10+. flatpanelshd.com/news.php?sub...

flatpanelshd.com

Netflix adds HDR10+ streaming alongside Dolby Vision

Good news for owners of Samsung TVs

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