Custom OLED Rolling Scans -- Custom Built OLED Monitor

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Custom OLED Rolling Scans -- Custom Built OLED Monitor

Postby matteo » 11 May 2017, 10:03

Hello everyone. I've been using this forum as a reference for various monitor-related stuff for some time, but this is actually my first post. Recently I've been thinking about buying an oled panel to use with a controller board designed to accommodate my needs, also as a means to deepen my understanding of a subject I'm interested in, even if I end up not doing it. I found Blur Busters to be a great source of knowledge in this regard. Problem is I'm not able to process that huge amount of information since I don't have any kind of electronics or computer engineering background. I've been reading a lot in the last few days but all I was able to understand are the principles I need to understand. I know I can't do much by myself so, for start, I was thinking about buying a custom-made controller to drive my panel of choice, but I must at least be able to explain what I want in a comprehensible way. So I'd really appreciate if someone could help me clarify a few things.

The panel would be a SONY ECX112AKU-6 oled 1080p 60hz 10bit LVDS. From what I understand Sony monitors with this panel use rolling scan with 7.5ms pulses. I'd like the controller to have adjustable scanning speed with option to disable strobing effect, to have selectable voltage boost to compensate rolling scan dimming, to support 1080p 60+hz overclock in order to reduce flicker introduced by rolling scan, and to be low latency.

Is that possible? How much would the voltage boost affect panel lifetime, and what would be a safe boost value for an oled panel? Do oled panels have any complication regarding overclock? Is it possible to have, say, both 75hz overclock and reduced scanning time to 2ms(time for pixels to reach maximum brightness) along with 3x brightness boost to compensate 2/[(7.5/16.67)*13.33] = 33.33% resulting brightness? Would voltage boost affect color reproduction, and if so can it be re-calibrated to correct it? Is there a way to improve overclocking capability with relatively simple hardware modifications?

I apologize for my English and for every stupid thing I might have written, but as I said I'm no expert. Thank you in advance.
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Custom OLED Rolling Scans -- Custom Built OLED Monitor

Postby Chief Blur Buster » 11 May 2017, 12:29

-- OLEDs are very sensitive to burn-in, so you can't give them much of a voltage boost like you can for LED backlights.
-- Those tiny pixels are extremely sensitive to being burnt out, with permanent burn-in, and that's also why some of them don't even have an option to disable strobing. Turning off strobing would accelerate burn-in to a degree, and the pixels are already essentially overdriven as it is -- pushing the specs of the OLED pixels already.
-- You won't be able to do a 3x boost. A little boost, yes -- the shorter the rolling scan window, the slightly brighter you can drive them, but you will still get burn-in risk. But it might be a calibration nightmare.

A little known piece of OLED history: The founder of Oculus (VR headset manufacturer) was a beta tester of Blur Busters TestUFO Motion Tests almost a year before Facebook purchased Oculus. (And half a year before TestUFO launched to the public!) They also tested LightBoost monitors, and realized that blur reduction was going to be very critical to VR. Apparently, this led to Oculus' decision to use a pulsed OLED (low-persistence rolling scan OLED). We ended up being a big butterfly in the Chaos Theory of the eventual chain of decisions leading to first Oculus rolling-scan OLED...

Some ideas
-- Adjustable-height rolling scan window
-- Multiple rolling scans (double-window) in the same refresh cycle
-- Use both the OFF scan / ON scan to both do ON scans instead -- 120Hz nonstrobed using 1/60sec scanouts
See images below.
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Custom OLED Rolling Scans -- Custom Built OLED Monitor

Postby Chief Blur Buster » 11 May 2017, 12:38

Many of us are familiar with how OLEDs achieve rolling scans to reduce motion blur.
And several readers already know Why Do Some OLEDs Have Motion Blur?.

Here's a high speed YouTube video of a rolling scan OLED (Sony TriMaster PVM-1741, but PVM-2541 is similiar too)

phpBB [video]


Now, here's the first set of images I've PhotoShopped up.
I'll probably insert these images into a new article soon.

Image

Image

Image

Motion blur comparision:
8ms = 50% less motion blur than normal 60Hz
4ms = 75% less motion blur than normal 60Hz
2ms = ~87% less motion blur than normal 60Hz
OLED pulse width (ms) creates MPRT of the same value (ms). MPRT = Moving Picture Response Time.

I'm creating more images, for unusual OLED-driving ideas (double-window rolling scans, true 120Hz via 1/60sec scanouts)
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Re: Custom OLED Rolling Scans -- Custom Built OLED Monitor

Postby Chief Blur Buster » 11 May 2017, 13:11

Here's the dual-rolling scan idea of mine:

It's possible to get true 120Hz refresh cycles using 1/60sec scanout, by using multiple rolling scan windows. If addressing speed is a problem, try half vertical resolution if you can inject voltage into two rows of OLED pixels simultaneously for longer period than a faster scan velocity.

This element addition is patent-free (assuming nobody else already patented this element before May 11, 2017). I have no knowledge of such prior art. I hereby put this idea under Creative Commons CC-by-SA 3.0, please credit Mark Rejhon of Blur Busters if monitor manufacturers take these ideas. Free, no charge. (But feel free to send us a monitor!)

Image

This will only work if you can address 4 rows simultaneously (two ON scans, two OFF scans) at a scanrate-limited speed (60Hz scan). I don't know if the OLED panel you choose, can do this, but if it does, this is a legitimate solution to pull 120Hz out of 60Hz. Metaphorically speaking, this is like a theoretical CRT with two electron guns that are scanning (temporally) different parts of the same CRT.

Pros:
- Low persistence! CRT motion clarity.
- Flickers comfortably at 120Hz rather than uncomfortably at 60Hz. No double image effect during motion!
- True 120Hz achieved at 60Hz scanrates. Full motion resolution of 120Hz!
- Spend more time sending voltage to OLED pixels. Improve OLED GtG accuracy.
- Twice as bright as 60Hz for the same persistence (pulse width)

Cons:
- 120Hz with the scanout lag of 60Hz. (Note: Less important for VSYNC OFF gamers)
- The same skew effect of 60Hz.
- Requires four-channel scanout

Applicable Only To These Assumptions:
- Useful if electronics is scanrate limited. (Can't scan faster than 1/60sec)
- Only if electronics allows addressing 4 pixel rows simultaneously (2 concurrent ON passes, 2 concurrent OFF passes)

For the skew effect, see http://www.testufo.com/blurtrail in full screen mode; that line will tilt on a 60Hz non-strobed displays, including on iPads and smartphones. A true 120Hz scanout (1/120sec) has less skew effect.

NOTE: Still requires buffering of refresh cycles (1 extra buffer), since display cables are only transmitting 1 refresh cycle at a time and you're scanning-out 2 separate refresh cycles simultaneously onto the same 2-dimensional plane (albiet in scans temporally-spaced 1/120sec apart, preserving the full 120 Hz motion resolution for each pixel).
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Re: Custom OLED Rolling Scans -- Custom Built OLED Monitor

Postby Chief Blur Buster » 11 May 2017, 13:46

And a different dual rolling scan without flicker -- which may be easier on existing OLED panels to coax them to do 120Hz.

May be good for two-channel OLEDs: If you can only address two rows of pixels simultaneously (an ON scan and OFF scan), you could hijack the electronics to make both of them ON scans (if the chips let you do so). Refreshing 120Hz full-persistence frames (no strobes) using rolling scanouts at 1/60sec velocity chasing behind each other by 1/120sec (8.3ms). So it's like a CRT with two electron guns, scanning simultaneously onto different parts of the same screen. Two refresh cycles being painted in different parts of the screen at the same time. It still preserves the "each pixel is refreshed exactly 120Hz" factor, and the scan is still sequential, so you get most of the 120Hz benefits.

This element addition is also patent-free (assuming nobody else already patented this element before May 11, 2017). I have no knowledge of such prior art. I hereby put this idea under Creative Commons CC-by-SA 3.0, please credit Mark Rejhon of Blur Busters if monitor manufacturers take these ideas. Free, no charge. (But feel free to send us a monitor!)

Image

This will only work if you can address 2 rows simultaneously (two ON scans. Skipping the OFF scans) at a scanrate-limited speed (60Hz scan). This will have more motion blur than a strobed rolling scan, but will still have half the motion blur of 60Hz.

Pros:
- True 120Hz achieved at 60Hz scanrates. Full motion resolution of 120Hz!
- Spend more time sending voltage to OLED pixels. Improve OLED GtG accuracy.
- Flicker Free! Full brightness.
- Only two channels needed for scanout

Cons:
- More motion blur than strobed (impulse-driven) displays.
- Avoiding strobing makes OLED more prone to burn-in
- 120Hz with the scanout lag of 60Hz. (Note: Less important for VSYNC OFF gamers)
- The same skew effect of 60Hz.

Applicable Only To These Assumptions:
- Useful if electronics is scanrate limited. (Can't scan faster than 1/60sec)
- Assumes that the "OFF" pass can be modified to be a second "ON" pass instead. Electronics that do rolling scans and normally allow a simultaneous "ON" pass and an "OFF" pass might in theory be coaxed to do two simultaneous "ON" passes instead. Depending on how the panel is designed.

NOTE: Still requires buffering of refresh cycles (1 extra buffer), since display cables are only transmitting 1 refresh cycle at a time and you're scanning-out 2 separate refresh cycles simultaneously onto the same 2-dimensional plane (albiet in scans temporally-spaced 1/120sec apart, preserving the full 120 Hz motion resolution for each pixel).
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Re: Custom OLED Rolling Scans -- Custom Built OLED Monitor

Postby Chief Blur Buster » 11 May 2017, 14:14

What's amazing is that doing multiple scanouts simultaneously apparently doesn't have many side effects (except amplified skewing which you already see at 60Hz horizontal movement situations. And depending on how buffering is achieved, a very slight amount of lag -- but less lag than strobed LCD such as LightBoost/ULMB if done properly)

The above suggestions, may eventually be adopted as a mechanism of working-around certain kinds of OLED limitations.

In theory, this is scientifically how a 1000fps @ 1000Hz OLED could possibly be achieved someday on a 120Hz OLED panel assuming it had enough scanout channels (8 of them). For a 120Hz OLED, you would only need only 8 scanout channels to achieve 960Hz! (960 / 120 = 8). That's 1ms persistence (1ms MPRT) without strobing. 1 pixel of motion blur during 1000 pixels/second motion, just like ULMB or LightBoost at shorter pulse widths Alas, you'd need an older game (CS:GO) capable of achieving 1000fps on current high-end GPUs.

Image

But that is 1ms full persistence with no strobing, no flicker -- true PWM-free low-persistence. Blur reduction achieved by overkill Hz instead of strobing. Indeed, this would extremely hard, but this multiple-scanout technique may make this possible in scanout-rate limited situations (aka needing to spend lots of time sending voltage into each pixel row) -- achieving higher refresh rates than otherwise currently easy or possible.

NOTE: Overclocking Margin experiments
You may want to experiment with larger overclocks (e.g. 90Hz and 120Hz). Oculus essentially overclocked a smartphone OLED to 90Hz and added a rolling scan to it. There's a case of a 60Hz laptop LCD being successfully overclocked to 180Hz. Even though OLED pixels are very fast, OLED pixel transition accuracy can still become more inaccurate when overclocked so you can get some distortions (gamma curve changes, inconsistencies, other effects, etc). You might find no overclock margin (75Hz) or you might find a huge overclock margin (>120Hz) -- keep an open mind.
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Re: Custom OLED Rolling Scans -- Custom Built OLED Monitor

Postby matteo » 11 May 2017, 14:44

Wow! I am very grateful for the incredibly exhaustive and quick answer. Thank you very much. Considering my lack of knowledge I understand the principles but I would have no idea how to implement any of the solutions you posted (fortunately that would not be my job). Nonetheless I am impressed by the tricks you conceived to achieve effective 120hz on a 60hz panel. Very clever! I'm sure someone more competent than me will be able to appreciate them even more. The question is probably very stupid, but how is vsync on able to do its job with 120hz on a 60hz panel? Each of the two off scans have a corresponding vertical blank interval so it can't tell the difference with a "true" 120hz? From what I understand these are the possible cases:

1) Electronics is not scanrate limited
Overclock + rolling-scan window height adjustment + slight voltage boost
2) Electronics is scanrate limited
a) Can address 4 rows simultaneously
Double-window rolling-scan + rolling-scan window height adjustment (requires extra buffer) + slight voltage boost
b) Can address 2 rows simultaneously
Double scan without strobing (requires extra buffer) (already having the display always on, no voltage boost here)

I hope the number of addressable rows is indicated in the panel datasheet, if I can ever get my hands on one. Same for limited scanrate. I'm not sure anymore if boosting voltage, even by a small margin, is a good idea. In the end with option 2b (which I prefer) and 2ms window height I should lose 46.67% brightness, which is not such a tragedy. The real tragedy could follow the answer to my quote request for such an implementation. I hope at least to be able to make myself clear about what i want.

Thank you again for your time and your knowledge. I appreciate it very much.

edit:
Why are options 2a and 2b only achievable if scanrate is limited?
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Re: Custom OLED Rolling Scans -- Custom Built OLED Monitor

Postby Chief Blur Buster » 11 May 2017, 15:05

matteo wrote:Wow! I am very grateful for the incredibly exhaustive and quick answer. Thank you very much. Considering my lack of knowledge I understand the principles but I would have no idea how to implement any of the solutions you posted (fortunately that would not be my job).

We're happy to help whomever wants to attempt this.

Your inquiry resulted in the creation of pretty eye candy that I've been long meaning to create for an eventual Blur Busters article. Guess that article is going to arrive a little sooner. ;)

matteo wrote:Nonetheless I am impressed by the tricks you conceived to achieve effective 120hz on a 60hz panel. Very clever! I'm sure someone more competent than me will be able to appreciate them even more. The question is probably very stupid, but how is vsync on able to do its job with 120hz on a 60hz panel? Each of the two off scans have a corresponding vertical blank interval so it can't tell the difference with a "true" 120hz? From what I understand these are the possible cases:

To help make it easier to think: Scanout on a cable doesn't have to be the same thing as scanout on a panel.

- Yes on CRT it can be synchronous.
- Yes on most gaming LCDs (Instant Mode / Lagless mode) it can be synchronous to zero-out input lag.
- Yes (when it's synchronous) the Large Vertical Total tricks is useful for reducing strobe crosstalk.

Since 1930s, analog displays had to scan synchronously directly off the cable, they don't have "memory" needed for scan conversion.
However, today, digital displays don't *NEED* to do it the same way. Scanout is still important for cables because it's a convenient serialization of a 2D image into a single stream of pixels over a wire (aka a video cable).

Scanout on cable doesn't have to be same thing Scanout on Display Panel
But today, display scanout can be totally different from cable scanout. Not all display use scanout synchronous to scanout on the cable. The original video signal retains it full VSYNC, but digital display panels don't need to treat VSYNC the same way (except as a signal for other purposes, such as "Hello, it's time to begin buffering this new refresh cycle for your custom digital refresh logic." equivalent -- like DLP/Plasma needs to do).

Scanout is still used today on cables because it's a convenient serialization of a 2D image (image) into 1D (wire)
The pictures you see on your monitor comes from (essentially) comes from a single binary stream (sequence of 1's and 0's, at 24 bits per pixel, hundreds of million pixels per second for gaming monitors). Scanout is still important at the cable level as you're rapidly transmitting millions of pixels over a wire, so you're scanning out the image, one pixel at a time. Left to right, then top to bottom, calendar-style fashion. Formerly that was over analog cable. But nowadays today DVI, HDMI, DisplayPort. Still a sequential scanout today. That metaphorical equivalent of a 1930s stream train is still a great 2010s bullet train today. However, when the pixels are finally inside the monitor (e.g. in a buffer), the display doesn't have to display (scanout) the same way as the cable did. It may do a totally different image-painting technique than scanout from GPU over the cable. ...Heck, if cable scanout was slow enough, a mechanical computer monitor could just use robotic crayons or pencils to draw the refresh cycles -- that would be quite the Rube Goldberg display with a very low refresh rate!...

Vertical Blanking Intevals (VBI) -- Including VSYNC -- is in theory obsolete
It stays around because of legacy purposes. In theory, VSYNC could be eliminated from digital display signals, but that eliminates backwards compatibility, and not all electronics are fast enough to instantly begin handling the next refresh cycle immediately after the prior, and not all electronics buffer the refresh cycles either. Yes, it is impressive that a 1930s signal still digitally exists on HDMI and DisplayPort cables. But then "VSYNC OFF" would need to be renamed to "Wait For Next Refresh Cycle = OFF" if we killed VSYNC from all cables and all displays (even if the panel doesn't use VSYNC, it still needs to understand VSYNC coming in on the cable). They still even use VBI for the variable refresh rate technologies (FreeSync, VESA Adaptive-Sync, and HDMI 2.1 VRR -- all virtually identical).
Variable Refresh Rate technologies and VBI: In fact, FreeSync modifies VBI in realtime. It is easily 100% convertible from digital into analog using simple DP/HDMI/DVI-to-VGA adaptors -- and apparently allowing variable refresh rate to sometimes successfully work on certain old analog multisync CRTs in tests. (In theory, nothing prevents VRR on CRT natively -- Vector CRTs were always variable refresh rates -- like the old 1982 Star Wars arcade machines that used line art)

DLP/Plasma Require Scanout Conversion (from original video signal)
Some display technologies need to do this (e.g. plasma, DLP) because they do ultrarapid scanouts of low-resolution pulse-width-modulated pixels at ultrahigh frequencies. For example, plasma subfields (often has very low color resolution -- they look like christmass-tree-sparkly images in high-resolution high speed video) are often refreshed at 600Hz. And DLP projectors use ultra rapid cycling of all tiny mirror pixels on a tiny chips -- that's done by converting the normal 60Hz scanouts (on cable) to an ultra-high-frequency scanout (kilohertz league, 1-bit ON|OFF). The rapid 1-bit flickering (ON/OFF) of each DLP pixel hundreds of times a second is what generates the brilliant 12-bit colors you see today in 4K DLP cinemas today...

Multiple simultaneous scans on OLED is just another form of scanout conversion (from original video signal)
The dual-scan OLED is no different of a "scanout conversion" logic (and even far simpler scanout conversion than plasma/DLP, in fact!), it's simply conversion of the ordinary scanout on the cable to the display's native scanout. Not all display panels need VSYNC (formery used to give CRT electron guns enough time to move back to the beginning of the display -- upper-right corner) and the electronics can completely eliminate VSYNC (zero waits between refresh cycles) or even overlap refresh cycles (like my diagrams).

Some displays use a different scanout direction
Your Samsung Galaxy S8 smartphone uses a bottom-to-top scan. Some iPad models use a left-to-right scan (when held with Home button pointing down) but not all of them. It's also possible that scanout on a display can be different than scanout direction over video cable (scanout conversion logic -- via buffered frames).

The GPU doesn't do anything different -- it keeps delivering the frames to the monitor (with normal VSYNC embedded in the signal on the cable). Display can simply internally convert this all to a different scanout mechanism to achieve specific goals (e.g. making 1-bit DLP pixels create 10-bit color for example)

matteo wrote:1) Electronics is not scanrate limited
Overclock + rolling-scan window height adjustment + slight voltage boost
2) Electronics is scanrate limited
a) Can address 4 rows simultaneously
Double-window rolling-scan (requires extra buffer) + rolling-scan window height adjustment + slight voltage boost
b) Can address 2 rows simultaneously
Double scan without strobing (requires extra buffer) (already having the display always on, no voltage boost here)

Essentially, yep.

matteo wrote:Why are options 2a and 2b only achievable if scanrate is limited?

Sorry about the confusion. It's not limited to that. But you'll prefer to have faster scanouts if you *can* do faster scanouts. Doing scanouts synchronously off the cable can be made essentially laglessly. Display engineers have to do creative work arounds for display panel quirks and limitations.
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Re: Custom OLED Rolling Scans -- Custom Built OLED Monitor

Postby matteo » 11 May 2017, 15:30

Thanks again! You've been a great help. It will take some time for me to digest everything you posted, but now I'm more exited than before about this project. If I can actually find one of these panels, I don't think I will be able to resist anymore!
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Re: Custom OLED Rolling Scans -- Custom Built OLED Monitor

Postby Chief Blur Buster » 11 May 2017, 15:33

P.S. Datasheets for OLEDs are often downloadable at Panelook.com
There's a datasheet PDF download for the Sony ECX112AKU-6 OLED panel:

http://www.panelook.com/ECX112AKU-6_SON ... 23451.html

You do need to become an $800/year member of Panelook.com to download unlimited datasheets of all known panels in their database, but it is worth it if you intend to play with panels. So as more OLED panels arrive, you'd be able to hunt down the baddest OLED with the biggest number of channels, to pimp the Hz through them (as soon as they appear on Panelook).

So -- essentially, in theory -- for the price of one high-end gaming monitor ($800) -- plus the cost of parts purchased off places like Alibaba, etc -- a very experienced electronics engineer can be their own "homebrew monitor manufacturer" playing with prototypes, custom TCONs, FPGAs, etc, mad-scientist style. Or a few/several thousand dollars given to someone else to experiment for you. Some Blur Busters visitors here (such as zis) might even be able to help work with you to pull off such dream OLEDs (if you pay him to do it). But he's super busy with his projects, people like him has the skillz to do the stuff I desctibe in this thread. So he might not be able to do it.

It may also be possible to grab these datasheets from elsewhere (e.g. somebody else who's a member of Panelook.com).

(Paging zisworks to look at this thread -- they're a Blur Busters Forums member. Maybe they can help you create this dream OLED. Or some other company. Obviously, you might need to 'pitch in some capital' to get things moving forward, but anything's now possible with the falling prices of homebrew prototyping -- with the right low-level programming/electronics skillz)
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