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TV backlight compensation (2020)

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Re: TV backlight compensation (2020)

#41

Post by EZ-Cheeze »

londons_explore wrote: post #39
EZ-Cheeze wrote: post #35

Earlier quoted context omitted.

I want to be able to edit anything on my screen in ways defined by me: "hide any faces" "put a red circle around any animal" "hide any word under three letters" http://zeroprecedent.com/lore/flipside.html

Well now you have all the building blocks to implement it...

I'll do it when I can just tell the computer to do it - maybe 2024

It will be interesting to rewatch movies with all the faces blanked out - they're eye-magnets that prevent you from noticing other details, for example in body language

Re: TV backlight compensation (2020)

#42

Post by sss111 »

serd wrote: post #22
empiricus wrote: post #20

Earlier quoted context omitted.

I don't see how the TV can compensate for the burnin without having an external picture of the screen. I have a couple of years old OLED TV, and it has burn in... The Netflix logo, the netflix animation, and subtitles are quite visible all the time now. This is despite running periodically the TV pixel refresh or however it is called...

Could you share a photo? I'd really like to see that.

second this!

Re: TV backlight compensation (2020)

#43

Post by RajT88 »

adrianN wrote: post #15
tgsovlerkhgsel wrote: post #13

Earlier quoted context omitted.

If you're not doing it as a hobby, the one-off effort put into repairing an item (or in this case, engineering the correction) is also "waste". If you want to dedicate that time to improving the planet, avoiding the waste of one TV is likely not a better use of your time than e.g. fixing some bug in some popular open source software that causes it to be less efficient. Let's say you make a change to Firefox that make…

Fair point, but I bet that making Firefox take 0.1W less on average is vastly more work that fixing a TV image. And if you write blog post about it, maybe other people can fix their TV with less work.

I don't know if I am going to ever fix a TV this way.

But the knowledge of how to create a custom shader is going to come in handy one day. More and more I am finding, most knowledge comes in handy some time. You just have to remember at the right time what is possible and go refresh your memory on it.

Re: TV backlight compensation (2020)

#44

Post by franky47 »

EZ-Cheeze wrote: post #41
londons_explore wrote: post #39

Earlier quoted context omitted.

Well now you have all the building blocks to implement it...

I'll do it when I can just tell the computer to do it - maybe 2024 It will be interesting to rewatch movies with all the faces blanked out - they're eye-magnets that prevent you from noticing other details, for example in body language

Funny how recent developments in AI have warped our comprehension of what is easy to ask to a computer vs what is hard.

Obligatory related XKCD: https://xkcd.com/1425

Re: TV backlight compensation (2020)

#45

Post by anon4584 »

adrianN wrote: post #15
tgsovlerkhgsel wrote: post #13

Earlier quoted context omitted.

If you're not doing it as a hobby, the one-off effort put into repairing an item (or in this case, engineering the correction) is also "waste". If you want to dedicate that time to improving the planet, avoiding the waste of one TV is likely not a better use of your time than e.g. fixing some bug in some popular open source software that causes it to be less efficient. Let's say you make a change to Firefox that make…

Fair point, but I bet that making Firefox take 0.1W less on average is vastly more work that fixing a TV image. And if you write blog post about it, maybe other people can fix their TV with less work.

There are other ways to improve the planet as well.

If everyone spent 2 hours a year removing washed up waste from the beaches, it would have made a big difference.

Re: TV backlight compensation (2020)

#46

Post by comboy »

Rygian wrote: post #24

This is almost identical to a problem I'm trying to solve, which is to turn a potato-quality picture of a sheet of paper into a clean scan, turning whatever levels of gray conform the paper background become a uniform #ffffff white. The obvious solutions (equalizing, converting to bitmap, …) don't work because what's white in the top left (say #ccc) is wildly different from what's white in the bottom right (say #888)…

Just so you know, there are many scanner apps which solve this problem already, not sure how many of them are open source though.

Re: TV backlight compensation (2020)

#47

Post by londons_explore »

speedgoose wrote: post #38
londons_explore wrote: post #28

Gnome (Ubuntu, Linux) allows a custom shader to be applied to the whole desktop, including fullscreen apps. Here is an up to date fork with some example shaders: https://github.com/Hello1024/gse-shader I use it to make sure a 'sensitive' pixel on my screen never turns on (it's a row of pixels which, if the difference between it and the pixels to the side have more than a certain difference in brightness, the whole sc…

How did you manage to find the issue?

I noticed the screen only died when playing videos and always died at the same point if I rewatched a video. Notably, greyscale videos never caused the issue. Then I went through a video frame by frame to get to the frame it died on. Then I erased parts of the frame to find which part caused it. Eventually I found that if the red or blue pixel in the 481st column and the green pixel in the 482nd column have a difference of brightness of too much, and neither are 255 or 0, the screen dies.

I'm pretty sure the problem is the column drivers (which put data onto the column lines). They take in serial data, and my 1920 screen has 4 column drivers, each responsible for 480 columns, so the 481st pixel is the first column that the 2nd column driver deals with.

It uses more power during the row sync pulse (because it has to drive all the column lines to the correct voltages for whatever is being displayed). It uses more power for grey values (because 255 or 0 are solid on or off, while mid values are typically dithered, wasting energy in the column capacitance). I would guess all these worst-case events for power consumption within the column driver, combined with probably 'barely passing qa' silicon, means that in edge cases the power sags, something gets reset, and the whole screen fails.

So my fix is a shader to make sure the worst case conditions can never happen all at once. Visually, it isn't really noticeable. And with more work it could probably be turned into something that could be shipped to customers (within the GPU driver) without any customer complaining (for example if you are a laptop manufacturer who has purchased millions of screens with this fault).

Re: TV backlight compensation (2020)

#48

Post by deergomoo »

nottorp wrote: post #33
ifqwz wrote: post #27

The quality of computer monitors is appalling - after buying and returning several monitors because of quality issues, I briefly considered doing this system-wide to fix colour uniformity problems. Eventually I chose to keep my old monitor instead. It has uniformity problems as well but it doesn't cost me $1000 extra to keep. But it's a damn shame that you can't throw enough money at manufacturers to make them make m…

You talking about mainstream "gaming" monitors? I'm just a programmer and gave up on those long ago. Getting entry level monitors targeted at graphic designers now. Namely Asus ProArt and I think Dell has similar stuff? They don't have 240 Hz and sub 0.01 ms response times though, so if you're buying your hardware based on bigger numbers in specs they won't do. They're probably not that great for actual designers eit…

> Asus ProArt

I’m using one of these and I’m very happy with it. Reasonable price, 75Hz, supports USB-PD + has its own USB ports so I can one-cable it with my work laptop.

Most importantly they come factory calibrated. I consider reasonable colour reproduction important even though I only use it for programming. I stare at this thing for 8 hours a day, it needs to look good.

In fairness I also have a 165Hz LG UltraGear gaming monitor, and the image quality is almost as good. My only complaint is the black levels and grey uniformity suck, but for someone who wants performance and quality it’s a decent option.

Re: TV backlight compensation (2020)

#50

Post by dontlaugh »

bzzzt wrote: post #17
rixrax wrote: post #11

I wonder if this is so 'generic' that e.g. AppleTV could add support for this? Take a photo of your TV with an iPhone when AppleTV is showing test image. And then the AppleTV output is calibrated appropriately to compensate for uneven backlight.

Calibrating color with an iPhone is already a feature in tvOS, so correcting for local errors looks like a nice improvement in that direction.

Sadly it only works with iPhones that have FaceID.
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