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pekka paalanen pekka paalanen 13 mar 2025 wayland color management sdr vs hdr and marketing this time i have three topics first i want to promote the blog post i wrote to celebrate the landing of the wayland color management extension into wayland protocols staging area it s a brief historique of the journey second i want to discuss sdr and hdr video modes on monitors and tvs i have seen people expect that the same srgb content displayed on the sdr video mode and the hdr bt 2100 pq video mode on the same monitor will look the same and they can arbitrarily switch between the modes at any time i have argued that this is a false expectation why monitors tend to have a slew of settings i tend to call them monitor knobs there are brightness contrast color temperature picture mode dynamic contrast sharpness gamma and whatever many people have noticed that when the video source puts the monitor into bt 2100 pq video mode the monitor locks out some settings often brightness and or contrast included so sdr and hdr video modes do not play by the same rules hence one cannot generally expect a match even if the video source does everything correctly third there is marketing have a look at the first third of this video they discuss video streaming services tv selling and hdr from the picture quality point of view my take of that is that some most monitors and tvs come with a screaming broken picture out of the box because marketing has to sell them if all displays displayed a given content as intended they would all look the same major technology differences notwithstanding but marketing wants to make each individual stand out have you heard of tv calibration services if i buy a new tv from a local electronics department store they offer a calibration service for a considerable additional fee why would anyone need a calibration service the factory settings should be good right posted by pq at 11 40 no comments email this blogthis share to x share to facebook share to pinterest labels graphics wayland 26 jan 2022 a pixel s color this post was first published with collabora on jan 25 2022 a pixel s color my work on wayland and weston color management and hdr support has been full of learning new concepts and terms many of them are crucial for understanding how color works i started out so ignorant that i did not know how to blend two pixels together correctly i did not even know that i did not know i was just doing the obvious blend and that was wrong now i think i know what i know and do not know and i also feel that most developers around window systems and graphical applications are as uneducated as i was color knowledge is surprisingly scarce in my field it seems it is not enough that i educate myself i need other people to talk to to review my work and to write patches that i will be reviewing with the hope of making it even a little bit easier to understand what is going on with color i wrote the article a pixel s color the article goes through most of the important concepts trying to give you a programmer a vague idea of what they are it does not explain everything too well because i want you to be able to read through it but it still got longer than i expected my intention is to tell you about things you might not know about so that you would at least know what you do not know a warm thank you to everyone who reviewed and commented on the article a new documentation repository originally wayland cm hdr extension merge request included documentation about how color management would work on wayland the actual protocol extension specification cannot even begin to explain all that to make that documentation easier to revise and contribute to i proposed to move it into a new repository color and hdr that also allowed us to widen the scope of the documentation so we can easily include things outside of wayland egl vulkan wsi drm kms and more i hope that color and hdr documentation repository gains traction and becomes a community maintained effort in gathering information about color and hdr on linux and that we can eventually move it out of my personal namespace to become truly community owned posted by pq at 13 59 no comments email this blogthis share to x share to facebook share to pinterest labels graphics 27 feb 2021 testing 4x4 matrix inversion precision it is extremely rare that a hobby software project of mine gets completed but now it has happened behold fourbyfour have you ever had to implement a mathematical algorithm say matrix inversion you want it to be fast and measuring the speed is fairly simple right but what about correctness or precision behavior around inputs that are on the edge you can hand pick a few example inputs put those into your test suite and verify the result is what you expect if you do not pick only trivial inputs this is usually enough to guarantee your algorithm does not have fundamental mistakes but what about those almost invalid inputs can you trust your algorithm to not go haywire on them how close to invalid can your inputs be before things break down does your algorithm know when it stops working and tell you inverting a square matrix requires that the inverse matrix exists to begin with matrices that do not mathematically have an inverse matrix are called singular can your matrix inversion algorithm tell you when you are trying to invert a matrix that cannot be inverted or does it just give you a bad result pretending it is ok working with computers often means working with floating point numbers with floating point the usual mathematics is not enough it can actually break down you calculate something and the result a computer gives you is total nonsense like 1 2 2 in spirit in the case of matrix inversion it s not enough that the input matrix is not singular mathematically it needs to be nice enough numerically as well how do you test your matrix inversion algorithm with this in mind these questions i tried to answer with fourbyfour the readme has the links to the sub pages discussing how i solved this so i will not repeat it here however as the tl dr if there is one thing you should remember it is this do not use the matrix determinant to test if a matrix is invertible yes the determinant is zero for a singular matrix no close to zero determinant does not tell you how close to singular the matrix is there are better ways read more posted by pq at 12 47 no comments email this blogthis share to x share to facebook share to pinterest labels math 20 nov 2020 developing wayland color management and high dynamic range this post was first published with collabora on nov 19 2020 fixed a broken link on jan 28 2021 wayland the protocol and architecture is still lacking proper consideration for color management wayland also lacks support for high dynamic range hdr imagery which has been around in movie and broadcasting industry for a while now e g netflix hdr ui while there are well established tools and workflows for how to do color management on x11 even x11 has not gained support for hdr there were plans for it alex goins deepcolor visuals but as far as i know nothing really materialized from them right now the only way to watch hdr content on a hdr monitor in linux is to use the drm kms api directly in other words not use any window system which means not using any desktop environment kodi is one of the very few applications that can do this at all this is a story about starting the efforts to fix the situation on wayland read more posted by pq at 19 44 no comments email this blogthis share to x share to facebook share to pinterest labels graphics wayland wayland design 28 oct 2016 waltham a generic wayland style ipc over network i have recently been occupied with a new project and being with a cold all this week so i have not been much present in the wayland community now i can finally say what i and emilio have been up to waltham for more information please see our annoucement posted by pq at 14 48 no comments email this blogthis share to x share to facebook share to pinterest labels network waltham wayland design 1 mar 2016 wayland has been accepted as a google summer of code organization now is a high time to start discussing what you might want to do for both student candidates and possible mentors students have a look at our project idea examples to get a feeling of what kind of projects you could propose first you will need to contribute at least a small but significant patch to show that you understand the workflow we have put some first task ideas together there are our application instructions for students of course all the pages are reachable from the wayland gsoc wiki page and also the wayland organization page if you want to become a mentor please contact me or kat the contact details are on the wayland gsoc wiki page note that students can also apply under the x org foundation organization since wayland is within their scope too and they also have other excellent graphics project ideas you are welcome to submit your wayland proposals to both projects posted by pq at 13 58 no comments email this blogthis share to x share to facebook share to pinterest labels graphics gsoc wayland 16 feb 2016 a programmer s view on digital images the essentials how is an uncompressed raster image laid out in computer memory how is a pixel represented what are stride and pitch and what do you need them for how do you address a pixel in memory how do you describe an image in memory i tried to find a web page for dummies explaining all that and all i could find was this so i decided to write it down myself with the things i see as essential read more posted by pq at 16 03 no comments email this blogthis share to x share to facebook share to pinterest labels graphics older posts home subscribe to posts atom about me pq msc eng in information technology self employed i am not in facebook or linkedin view my complete profile disclaimer all statements and opinions are 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