Gianni Rosato
@giannirosato.com
Multimedia Compression Engineer Mastodon: @gianni@disobey.net Web: https://giannirosato.com/ Work: https://halide.cx/
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 - 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.
github.com
Making Software: Image Compression www.makingsoftware.com/chapters/ima... Cool to see WebP addressed here too!
Making Software: Image compression.
Exploiting the quirks of human vision to make images smaller, without looking awful.
makingsoftware.com
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...
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.
rachelplusplus.me.uk
The Codec Wiki has moved from wiki.x266.mov to codecs.wiki – apologies for the down-time!
wiki.x266.mov
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!
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
An Updated Sponza glTF – Ignacio Castaño
ludicon.com
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
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.
halide.cx
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
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
v4.0.0 · Alliance for Open Media / SVT-AV1 · GitLab
[4.0.0] - 2026-1-23 API updates Major release with...
gitlab.com
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 - halidecx/fcvvdp: Fast CVVDP implementation in C
Fast CVVDP implementation in C. Contribute to halidecx/fcvvdp development by creating an account on GitHub.
github.com
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 - 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
github.com
Enhancing HDR on Instagram for iOS With Dolby Vision: https://engineering.fb.com/2025/11/17/ios/enhancing-hdr-on-instagram-for-ios-with-dolby-vision/ #av1 #vp9 #hdr
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
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
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.
giannirosato.com
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!
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...
github.com
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
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?
halide.cx
The Halide Compression website (halide.cx) now has an Atom feed – just paste the URL into your favorite RSS reader and you should be good to go!
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?
halide.cx
New blog post about my experiences using spark.js with three.js: www.ludicon.com/castano/blog... Re-posts and feedback appreciated!
three.js + spark.js – Ignacio Castaño
ludicon.com
Anyone using rss/atom readers can now type `giannirosato.com` into their reader to get my website's atom feed
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!
An Interview With Julio Barba | Halide Blog
halide.cx
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
Zola
Everything you need to make a static site engine in one binary.
getzola.org
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.
Tune 3: Still Picture is coming to SVT-AV1: https://gitlab.com/AOMediaCodec/SVT-AV1/-/merge_requests/2489#note_2704093242 Formerly Tune 4 in SVT-AV1-PSY. Thank you @juliobbv.bsky.social !
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 😉.”](https://cdn.bsky.app/img/feed_thumbnail/plain/did:plc:lj7y6n7ouwe2276ubo5cizaa/bafkreiabxrmpl67iegnifzu64fdckai6yjodzjneksoknqebyndshcjila)
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...
A Better Image Compression Comparison - Rachel++
rachelplusplus.me.uk
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
Improving AVIF in Open Source | Halide Blog
halide.cx
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.
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
