How do I stack two projectors to increase FPS?

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blurfreeCRTGimp
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How do I stack two projectors to increase FPS?

Post by blurfreeCRTGimp » 26 Sep 2022, 15:41

I have heard the chief make the suggestion that one can run multiple projectors in series for increased FPS using Genlock? I just got myself 2 Nebra Anybeam MEMS projectors and I am wondering what hardware I would need, or if I could configure my GPU (GTX 1060 3gb) to output frames in series?

Any help would be appreciated. I have already verified that I can run both together for higher resolution using Nvidia surround, but higher FPS would give more benefit to me than the raw resolution. This thing is amazing in the dark for retro gaming.

Its a very Jenky setup at this point, and its hard to get the projectors to be flush and seamless for surround, but not impossible. I don't have the right mounts, and there is unit to unit variance in the throw which means each needs to be at a varied distance to get the same size so they give me that bezelless giant image. : )

I can run 1280x1440 @60hz or 2560x720 @60hz. I would prefer being able to use these in series for 720p at 120hz. The extra resolution is nice, but since I don't have 4 of them, and my 1060 doesn't have the inputs, I cant get the nice even 1440p resolution that would be ideal.

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Re: How do I stack two projectors to increase FPS?

Post by Chief Blur Buster » 26 Sep 2022, 16:30

Do you know Windows Indirect Display Driver programming? Microsoft DDK has a sample that can be modified to create a custom display driver that can do this.

Refresh rate combining 2 impulsed projectors (CRT or laser or strobed LCD/LCoS) requires two video outputs with VBI that is 50% out of phase of each other, and a unified display driver that outputs every other virtualized refresh cycle to each output, round robin.

It’s key to 8K 1000fps 1000Hz using today’s projector tech. We’ve come up with open source algorithms which we are currently writing a white paper on.

Sixteen strobed non-subrefresh-temporal (non-DLP) 8K 60Hz peojectors can do 8K 960Hz via these surprisingly simple generic algorithms. But it requires impulsed tech (e.g. CRT or strobed LCD/LCoS) and writing your own custom display driver to output the out-of-phase signals.

You have the right projector tech for refresh rate doubling! Now add software and voila.
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blurfreeCRTGimp
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Re: How do I stack two projectors to increase FPS?

Post by blurfreeCRTGimp » 26 Sep 2022, 16:59

No, I do not know how to write my own display driver, I am not that advanced. Do you think there is any software out there that could do it?

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Re: How do I stack two projectors to increase FPS?

Post by Chief Blur Buster » 26 Sep 2022, 19:12

blurfreeCRTGimp wrote:
26 Sep 2022, 16:59
No, I do not know how to write my own display driver, I am not that advanced. Do you think there is any software out there that could do it?
No. This is a new field.

I anticipate that this will finally hit open source channels within a year or two, but you never know.
There's an increasing need for display simulators in an open source indirect display driver level for multiple needs:
- VRR simulation, like www.testufo.com/vrr
- Adding BFI, like www.testufo.com/bfi
- Display algorithm simulators (e.g. CRT electron beam simulation)
- Software based overdrive algorithms

But can also be used to this specific purpose too -- creating a virtual screen (virtualized Hz) and round-robin outputting them to different graphics outputs one at a time, for refresh rate combining purposes (via stacked projector approach).
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Re: How do I stack two projectors to increase FPS?

Post by thatoneguy » 27 Sep 2022, 06:34

Laser Beam Scanning is still a thing?
Are these just rebranded Sony MP-CL1's?
Seems to be that way.

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Re: How do I stack two projectors to increase FPS?

Post by blurfreeCRTGimp » 28 Sep 2022, 15:32

I don't know if its the same parts as in the Sony. It doesn't have the same functionality as the Sony ones did. I bought these because they were the only ones left on offer lol. I had to have a piece of this technology.

I am going to try for a 2560x720 surround setup, since I bought two. There is a unit to unit variance in terms of throw distance and I would need to do keystone adjustment to align them just right.

In a dark room with any 60hz content it is amazing. Has less motion blur then my SD Sharp CRT from 2002, likely due to not having phosphor decay time. The motion is very good, and I can resolve more by sight than I can on my XL2720 overclocked to 165hz with backliught strobing and a very low pulse width. Infinite contrast is very nice to have again, especially since it cost less than 1/3 the price of OLED. No burn in is also a huge plus.

I tested it first with a SNES classic playing on what must have been an 80 inch screen. Since the SNES classic is 720p 60hz it fit perfectly with the anybeam. Regular DVD's look exactly as they should look, not processed. and I'm getting their full motion resolution. There is laser speckle, but its super minimal at larger screen sizes on a white wall. Text is difficult to read, but I did not mess with clear type settings.

I wish there was someone hear who could write a driver like the chief mentioned, because I think at 120hz this tech would smoke everything. In terms of cost for what you get, this is amazing.

I posted on the CRTgaming subreddit when I got it, because its a great cheaper alternative.

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Re: How do I stack two projectors to increase FPS?

Post by thatoneguy » 28 Sep 2022, 18:45

blurfreeCRTGimp wrote:
28 Sep 2022, 15:32
*snip*
So it's probably a Celluon PicoPro rebrand then.

Bro, don't bother with stacking these projectors if resolution is your aim. If you want to get 120hz then great but the resolution is not 720p, not even close. Karl Guttag disproved this a long time ago.
The res is closer to 360p.

https://kguttag.com/2015/06/01/celluon- ... or-part-1/
https://kguttag.com/2015/06/02/celluon- ... echnology/
https://kguttag.com/2015/06/06/celluon- ... y-revisit/

https://kguttag.com/2012/01/09/cynics-g ... esolution/

Good that you're enjoying the motion(maybe you should do the UFOTest and post it here) but let's be realistic, the resolution and the actual image quality is way worse than even a cheap consumer CRT you might find in craigslist(sure that consumer CRT maybe won't have motion as smooth but the image quality will be way better and it's much more easily compatible with actual retro consoles).
Last edited by thatoneguy on 28 Sep 2022, 19:10, edited 3 times in total.

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Re: How do I stack two projectors to increase FPS?

Post by Chief Blur Buster » 28 Sep 2022, 18:57

blurfreeCRTGimp wrote:
28 Sep 2022, 15:32
I am going to try for a 2560x720 surround setup, since I bought two. There is a unit to unit variance in terms of throw distance and I would need to do keystone adjustment to align them just right.
To prevent pixel distortion in Windows, you may want to use 2560x1440i.

You can usually double your CRT refresh rate by going interlaced -- most CRT projectors can go double Hz at interlaced. You might need to use slightly larger VBIs to vertically stretch the image a bit, since you need to give the vertical deflection enough time to reset the scan to the top of the CRT, and double Hz (even interlaced) still halves the VBI time. (Double Hz requires double number of scanlines in VBI in order to keep VBI-time-constant, and that can eat into the bandwidth headroom of your RAMDAC).

But compensate for this, and the extra Hz is typically accomodated, unless it's unable to recharge the vertical deflection capacitor fast enough in between the more-frequent VBIs -- but usually most projectors keep up just fine at double interlaced Hz.

Technically you could attempt to stack the 2560x1440i as vertically perfect as possible, in order to try and create 2560x1440p at the double refresh rate. You'd simply use ordinary screen mirroring, except configure the other projector with 1 less scanline in the VSYNC and 1 more scanline in the porch, to force the even-odd scanline swap.

Both same Pixel Clock, except ToastyX would have 1 less in Vertical Sync and 1 more in one of the porches on one of the two projectors. The problem is forcing Windows to use one timings slot for one projector and a different timings slot for the other projector -- not sure if that is possible.

But if successful, this forces projector 1 to scanout the even scanlines, while concurrently projector scanout the odd scanlines. And vice-versa for next refresh cycle.

If you align perfectly, you're creating 1 progressive scan frame from 2 interlaced projectors! Creating a simpler refresh-rate-doubling effect. Your projector's geometry must be uncannily accurate, and your screen mirroring to be as in-sync as possible, since you're trying to align the odd scanlines between the other projectors' even scanlines. To simplify this, may require creation of custom test patterns (single-pixel scanline rainbow, color coded per projector), to assist your ultra-precise convergence work. And thermal expansion will be a royal pain, so warmup first...

Windows and graphics drivers, unfortunately, will be a major limiting factor, but theoretically ToastyX may be able to install display-specific EDIDs -- experimentation will be needed to see if it will successfully work with same-pixel-clock different-VBI-behavior.

This would be a clever way to get a double-Hz progressive scan image. A projector that can only do 150Hz interlaced can usually do almost 300Hz in interlaced (undocumented if you VBI-compensate -- might eat into Hz headroom and you may only get, say, 250-280Hz), and two projectors would conveniently combine the interlaced into progressive.

The bonus is you would only need to do simple ordinary screen mirroring between the two outputs. Must be two outputs from a single GPU to keep the dotclocks in perfect sync, as there's some clock drift between separate GPUs, that causes a VBI-slew effect. Then, even then, hopefully the GPU keeps the VBI relatively in sync, so a GPU driver restart (Restart64) may force the sync if the VBI's are accidentally time offsetted.
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Re: How do I stack two projectors to increase FPS?

Post by thatoneguy » 29 Sep 2022, 07:34

Chief Blur Buster wrote:
28 Sep 2022, 18:57
To prevent pixel distortion in Windows, you may want to use 2560x1440i.
Please refer to my post above yours.
Karl Guttag already proved years ago that these LBS(Laser Beam Scannng) pico projectors are nowhere near 720p but more like 640x360(if that).
So stacking 2 of these is absolutely pointless.

Also they do 60hz interlaced scanning apparently, not progressive, so that's even worse.
You'd have to stack up two projectors just to get 60hz progressive in that case.

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Re: How do I stack two projectors to increase FPS?

Post by Chief Blur Buster » 29 Sep 2022, 10:40

thatoneguy wrote:
29 Sep 2022, 07:34
Chief Blur Buster wrote:
28 Sep 2022, 18:57
To prevent pixel distortion in Windows, you may want to use 2560x1440i.
Please refer to my post above yours.
Karl Guttag already proved years ago that these LBS(Laser Beam Scannng) pico projectors are nowhere near 720p but more like 640x360(if that).
So stacking 2 of these is absolutely pointless.

Also they do 60hz interlaced scanning apparently, not progressive, so that's even worse.
You'd have to stack up two projectors just to get 60hz progressive in that case.
Oh... Right. If the projectors are limited to that, then you're definitely right.

I was borrowing on my CRT projector experience, assuming the projectors were multisync-capable. But if it's just a 640x360 pixel grid, even with an analog-driven laser -- scratch what I just said, it was more applicable to stacking 2 CRT projectors.
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