Can’t eliminate Crosstalk - XL2546

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Re: Can’t eliminate Crosstalk - XL2546

Post by Chief Blur Buster » 16 Mar 2018, 13:04

KKNDT wrote:The only thing I haven't tried yet is to reduce the dynamic range. I don't know whether it can be done by users.
That's easy -- it's just merely manipulating Brightness / Contrast. Either via monitor OSD (preferred) or via graphics drivers (fallback). You want to brighten blacks and dim the whites. Or use one of the "16-to-235" modes instead of the "0-to-255" modes. (some drivers have that option). You lose a little contrast and color precision.

But with this "reduce dynamic range" trick, you've intentionally added more overdrive overshoot headroom below black, and above white -- which can reduce ghosting effects for high-contrast color edges.
k2viper wrote:Got some XL2546 crosstalk pics from a Russlan forum user, they can be seen here: https://drive.google.com/file/d/1TzZTD5 ... v7mQR/view

I'd say its pretty similar to LG's crosstalk, but XL2546 definitely have much more obvious overshoot which overall makes picture look worse then LG's.
Large Vertical Totals will help hide the crosstalk zone offscreen on most of the 144Hz BenQ/ZOWIE monitors. The longer VBI gives more time for LCD GtG to complete between refresh cycles.

The end result is that you'll have more space to move the "crosstalk bar" (via "Strobe Phase" adjustments) off the screen before it wraps-around to the opposite edge of the screen -- imagine a Large Vertical total as virtual screenspace below bottom edge of screen or above top edge of screen, that provides "crosstalk bar hiding room".

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That's a scanout diagram of a Large Vertical Total via Custom Resolution Utilities.

This specific example is 100 refresh cycles per second, even though a display panel is scanned out in 1/144sec.

The bigger VBI -- the easier to hide LCD GtG in the VBI (aka VSYNC interval). The bigger the VT, the better. And it's easier to have larger VT at lower refresh rates. That's why lower-Hz strobing has less strobe crosstalk -- LCD GtG is hidden between refresh cycles = more strobe crosstalk disappears.

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....Now you're getting it! That's why Large Vertical Totals really help strobe backlights.

The bigger the Large Vertical Total, the easier it is to push the crosstalk zone off the screen edge before it "wraps around" to the top edge of the next refresh cycle.

The VBI height (the pause between refresh cycles) ideally needs to be taller than the crosstalk zone to more completely hide the worst strobe crosstalk between refresh cycles! That's the "Cramming LCD GtG pixel response into the Vertical Blanking Interval (VBI/VSYNC)" trick that strobe backlights do to bypass LCD pixel response limitations.

The VBI size is (Vertical Total - Vertical Active) -- so VT1350 on 1080p means you've got 1080 visible rows of pixels and 320 VBI rows of pixels as the pause between refresh cycles.

The VBI can even be bigger than the image. e.g. 60Hz with the scanout velocity of 240Hz -- approximately ~VT4400 works on certain 240Hz monitors. You open Custom Resolution Utility, go to highest Hertz, put radio button on "Pixel Clock" (lock the pixel clock) and then increase the Vertical Total to lower the refresh rate to your target refresh rate -- and voila. That's the Appendix A approach of http://www.blurbusters.com/crosstalk for creating brand new Large Vertical Total modes for an existing monitor. A quadruple VT (1/240sec) on 60Hz will create an approximately 12 millisecond VBI pause between the 4.2ms scanouts, big enough to drive the LCD GtG truck through, even for 5ms IPS and VA GtG.

There is no limit how big a VBI can be -- except the monitor's technological limitations on tolerating such a large VBI.

(FreeSync/VRR is simply a variable Vertical Total -- variable pause between refresh cycles).

For LG's case, the large-VT 240Hz mode is simply a 240Hz with the scanout velocity of 280Hz. :)
Which is why I am impressed at LG -- its unique ability to do Large Vertical Total at 240Hz!! It's only approximately 0.8ms VBI, so won't hide 1ms GtG (realworld >1ms GtG).

The HDMI 2 lag-reducing Quick Frame Transport is essentially a form of Large Vertical Total -- but you can do QFT tricks on any signal like DVI, DP, etc.
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Re: Can’t eliminate Crosstalk - XL2546

Post by Falkentyne » 17 Mar 2018, 02:35

KKNDT wrote:BENQ opens all the parameters to users. Theoretically, I don't think other models can do better strobe than a well optimized BENQ monitor with same panel.

Pulse width
Pulse phase
Overdrive in factory mode

VT
Rrefresh rate

I tried all the settings but still saw faint crosstalk. Strobe backlight requires very fast GtG to completely eliminate crosstalk. Maybe we need to count on the next GEN AUO panel as planed. (pushing the on/off, white>black response time on TN Film down from the current 5ms typical to 3ms before overdrive)

The only thing I haven't tried yet is to reduce the dynamic range. I don't know whether it can be done by users.
The overdrive changing in factory mode was new to the XL2730 (in a very limited way) and was only full range changing in the XL2735 and XL2540 and newer.

This setting was originally used on the old Mstar scalers and the firmware type, that was available on the Asus VG248QE and VG278, and the option "OD Gain" was there as well, although no one knew about it. It was useful in removing even the faintest overshoot from Lightboost mode.

The OD gain really needs to be used far more often on the XL2735, XL2540 and XL2546. It's VERY useful.

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Re: Can’t eliminate Crosstalk - XL2546

Post by Chief Blur Buster » 17 Mar 2018, 14:49

(Hmmmmmm. Thinking. Is there a VCP command for the OD gain?
Someone will need to do a little SoftMCCS hacking to find out)

If so, I could probably add additional adjustments (e.g. OD gain slider) to Blur Busters Strobe Utility (Version 2.2 or later).

The upcoming Version 2.1 has an offline TestUFO built in (no browser needed).
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Re: Can’t eliminate Crosstalk - XL2546

Post by Falkentyne » 17 Mar 2018, 17:15

Chief Blur Buster wrote:(Hmmmmmm. Thinking. Is there a VCP command for the OD gain?
Someone will need to do a little SoftMCCS hacking to find out)

If so, I could probably add additional adjustments (e.g. OD gain slider) to Blur Busters Strobe Utility (Version 2.2 or later).

The upcoming Version 2.1 has an offline TestUFO built in (no browser needed).
I don't know. I don't have any current Benq monitor :(
I do know that there was no VCP command for OD Gain on the VG248QE or VG278H.
I don't believe "Factory Menu" settings are exposed to DDC/CI, otherwise you would be able to do extremely dangerous stuff like change the Scaler bank, Panel SSC and other stuff that could brick the display.

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Re: Can’t eliminate Crosstalk - XL2546

Post by JR_Shoegazer » 31 Mar 2018, 13:45

So I’ve heard people talk about accessing the factory menu. I’ve tried to follow the steps I found online but I haven’t been able to get it to work. Does anyone have any tips? I wish I know someone in person who already had experience with this so they could just look at my setup in person because it’s definitely frustrating.

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Re: Can’t eliminate Crosstalk - XL2546

Post by PedanticFool » 31 Mar 2018, 20:05

Chief Blur Buster wrote:(Hmmmmmm. Thinking. Is there a VCP command for the OD gain?
Someone will need to do a little SoftMCCS hacking to find out)

If so, I could probably add additional adjustments (e.g. OD gain slider) to Blur Busters Strobe Utility (Version 2.2 or later).

The upcoming Version 2.1 has an offline TestUFO built in (no browser needed).
Can you expand on how the correct VCP command might be found with SoftMCCS? I've looked for an OD gain setting myself but with no luck.

I figured the best starting point would be to get the current values for every code from 0x00-0xFF and compare them to the current OD gain value displayed by the factory menu. I couldn't find an easy way to dump the contents of every code though, Tools>Refresh VCP Table seemed to only return the values for the codes listed in the capabilities string. I know this list is incomplete since it doesn't contain the StrobeEnable/StrobeLen/StrobePhase found in BlurBustersStrobeUtility.ini which work just fine.

I ended up using Tools>softOSD API command processor to grab the current values for each code from 0x00-0xFF manually with GetControl. This was awkward but seemed to work, 0x41 and 0x42 returned the current intensity and area settings but unfortunately no code returned a value which matched OD gain in the factory menu.

Is there anything else I can try? A few notes, my testing was done on an XL2540 not an XL2546. Additionally the monitor does not return VCP commands while in factory menu mode so it's necessary to first note down the current OD gain value in factory mode before power cycling the monitor and sending VCP commands.

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Re: Can’t eliminate Crosstalk - XL2546

Post by k2viper » 01 Apr 2018, 06:51

BTW LG 27GK750F-B, also has an Mstar scaler like Benqs and shows 4D, 4E, 4F controls as active. But unfortunately their values seems locked, they do not change if I send a new value to these VCP's. I tried to set these values by Strobe utility 2.0. Or maybe I'm doing something wrong?
What's the correct command for SoftOSD API to set a value to given VCP?

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Re: Can’t eliminate Crosstalk - XL2546

Post by Chief Blur Buster » 01 Apr 2018, 14:29

0x4D, 0x4E, and 0x4F are manufacturer-defined custom DDC codes used for various things. They are not standardized strobe adjustments. Sometimes monitors reject specific values, e.g. they might reject 0x0000 or 0xFFFF but mioght accept 0x180 or 0x179 or whatever. Sometimes they are 8-bit values and sometimes 16-bit values. You have to experiment and figure out what range-of-adjust they are by writing to the codes via SoftMCCS instead of via Strobe Utility.

I cannot provide help or technical support as Strobe Utility is specifically designed for BenQ-Zowie monitors at this time.
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Re: Can’t eliminate Crosstalk - XL2546

Post by k2viper » 02 Apr 2018, 01:31

Sure, I'm just asking if someone know how to set a value to a given VCP via SoftMCCS through its commandline api (SoftOSD API)?

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Re: Can’t eliminate Crosstalk - XL2546

Post by PedanticFool » 02 Apr 2018, 01:41

k2viper wrote:Sure, I'm just asking if someone know how to set a value to a given VCP via SoftMCCS through its commandline api (SoftOSD API)?
SetControl X Y - sets control X to hex value Y

http://forums.entechtaiwan.com/index.ph ... 0#msg26960

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