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4K DLP hack for 120 fps -- [for TI 4K projectors]

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4K DLP hack for 120 fps -- [for TI 4K projectors]

Postby RLBURNSIDE » 19 Feb 2017, 14:07

Hi guys, I figured I should share this here since this site is all about stuff greater than 60hz:

https://www.shadertoy.com/view/lslcRr

Here's a discussion on AVS regarding my idea to get 120fps in SDR and 96hz in HDR out of these new TI 4K projectors:

http://www.avsforum.com/forum/68-digita ... st50669905

http://www.avsforum.com/forum/68-digita ... st50886217

I believe it might just work based on the fact that they pass the 1 pixel-wide 4K torture test:

Image

You can see these new chips which have 2716 x 1528 native resolution, or 4M pixels, can indeed resolve every pixel in a UHD 2160p source image (8M pixels), by using what's known as "wobulation", i.e. showing 1/2 the pixels at time A and the other half at time B, both within the same frame duration as a standard 60hz frame.

It's similar to an idea I read here on Blurbusters (to give credit where it's due) about using the 3D mode on DLPs to engage 120 fps in 2D using SBS modes. But this is far better because it increases spatio-temporal resolution in both dimensions (space and time).

I also wrote a shadertoy for that here:

https://www.shadertoy.com/view/4sfcR8.

It works on my w1070.

The core of my idea is simply to exploit the fact that the second subframe needn't be sampled at the same time as the first, or even at the same offset.

It also should achieve stereoscopic 3D using VESA LCD-shutter glasses. I will be writing media player classic shaders to show movies on it and it should work even better in games because if you can do 60 fps at UHD then you can maybe do 120 fps at 2.7K (which is exactly half the number of pixels per frame, hence the same workload). Plus if you do it for stereo 3D you can also do VR SLI and single-pass stereo to render both eyes simultenously. Then it's just a matter of compositing the 2160p framebuffer in a similar way as I did in my shadertoy here.
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Re: 4K DLP hack for 120 fps -- [for TI 4K projectors]

Postby Chief Blur Buster » 19 Feb 2017, 14:43

Fascinating, 4K 120fps on a DLP projector!

Do these projectors have capability for BFI -- black frame insertion?

This will reduce persistence even further. Many 3D DLPs use a BFI to help accomodate shutter-switch delay in LCD shutter glasses (the amount of time for 3D glasses LCD shutter to fade open/closed between eyes). But a side effect of this BFI for 3D mode, is the reduction of persistence to approximately 1/4th as much motion blur as 60Hz DLP.

60Hz DLP -- 100% motion blur of 60Hz
120Hz DLP -- 50% motion blur of 60Hz (each frame visible for 1/120sec)
120Hz DLP + BFI -- 25% motion blur of 60Hz (each frame visible for 1/240sec)

This assumes 50%:50% BFI ratio. Sometimes the BFI ratio is adjustable (e.g. 60% picture, 40% black frame) so there is some fudge factor.
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Re: 4K DLP hack for 120 fps -- [for TI 4K projectors]

Postby Chief Blur Buster » 19 Feb 2017, 21:11

I've split the software-based black frame insertion driver/shader into a new topic:

Shaders/Drivers with software-based Black Frame Insertion

We can continue both discussion threads, they are both very useful topics with their own different spinoff benefits.
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Re: 4K DLP hack for 120 fps -- [for TI 4K projectors]

Postby BattleAxeVR » 14 Dec 2017, 11:49

For anyone interested, the new BenQ "4K" or "FauxK" DLP projector, model name w1700 (Europe) / HT2550 (US) uses a 1080p DMD and quad pixel shifting, operating at 240hz internally.

I wrote a proof of concept to see if, when you feed a custom packed 1:1 signal (8-bit 4:4:4 or RGB at 4K60) that you can pack four time-sequential 1080p frames into one 2160p frame and have the projector unpack it due to displaying those sub-frames in order:

https://www.shadertoy.com/view/Xl2cz3

If a high-speed camera capture of this shadertoy shows a sequence of solid colours via these new quad-shifting DLPs, then we have a method for displaying 1080p240 and if we further keep the spatial offset for each 1080p frame to match the offset of the pixel shifter / aka "wobulator" then you can get effectively 4K240hz.

For around $1500 US starting in January 2018. That's just on the shadertoy, for now, but there are ways to pack frames together digitally. I'm working on that but will not release it unless BenQ (or Viewsonic or anyone else using this new quad-shifting tech) sends me such a projector, free of charge, to develop it on.

It would require a 1:1 map so unfortunately 4K60 in HDR10 won't do, since HDMI 2.0a bandwidth limits us to 422 in 10-bit, however 48hz in 10-bit is exactly the same bandwidth as 60hz in 8-bit so it would be equally possible to achieve 4K 192hz in HDR using 1:1, assuming of course it's possible to push 10-bit at 48hz to these. I know 48hz is possible using a custom refresh rate on current 1080p DLPs, but only in 8-bit, 10-bit doesn't work (even when using YCbCr 4:4:4 which does allow 10-bit at 1080p30 IIRC).
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