display "equalization"

By: --- (---.delete@this.redheron.com), May 9, 2022 7:30 pm
Room: Moderated Discussions
I found this patent
which I consider exceptionally cool, even though its obvious when you think about it.

The idea is that a module in the display controller (for eg an iPhone) is aware of various "defects" in a screen, for example
- non-uniformity across the screen
- edge effects from the backlight
(these could be established at testing time)
- aging
- the effect on temperature on a display.

All this is put into tables, and a set of per-pixel brightness corrections are created which are applied to the image as it streams through.
On the one hand, yes, it's just like any sort of equalization.
On the other hand, neat!!! A simple way to make a screen look a lot better, and continue looking a lot better over a range of operating conditions and over a long time.

(When you start getting into the weeds, it is astonishing how much stuff there is in Apple's display controllers, like full-blooded neural nets for intelligent up-scaling! Of course the GPUs have the same, so in a sense it's not unexpected -- but it's also not something you immediately think of!

FWIW my tests suggested that for static scaling, Apple's solution is about as good as what's in my iMac Pro [so basically AMD as of 2017], though more dynamic (can upscale while resizing; the AMD solution uses a lower quality up-scaling while resizing, and snaps to the final quality when resizing ends). This static upscaling is REALLY good when it comes to text and sharp edges, and definitely better than just OK when it comes to textured content.

OTOH the Apple solution appears (both by patents and by eye) to not yet have any temporal component. So no temporal upscaling (as for games) and no use of frame-to-frame data to improve the quality of upscaling.
For TV content (ie using my Apple TV w/ A12) Apple is clearly superior to what's built into a recent LG OLED 4K TV for expanding the dynamic range of lousy old content (like old NTSC or 60s movies), but clearly worse when it comes to stuff that makes use of multiple frames (so upscaling fine detail, and faked smoothness of motion when you have this terrible [think documentaries] content that has been poured from 24 fps to 50fps PAL to 60 fps NTSC.

One interesting aspect this raises is that, I *suspect* the Studio Display will do above average not just in color constancy but also in correction for ambient lighting. I don't know the extent to which other monitors *in that price range* attempt this correction, not just at the basic brightness level but also at the more sophisticated ambient light color tracking [ie whitepoint correction] level.
However the Studio Display team [who appear to have dropped the ball on many things] appear also to have flubbed this, omitting a back-facing light sensor. So while the device can correct for strong light behind me, it can't correct for the color of the wall behind the monitor or bright lights behind the monitor. Oh well, maybe in two years they'll try a little harder. )
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display "equalization"---2022/05/09 07:30 PM
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