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Benq xl2411z Crosstalk

post #1 of 4
Thread Starter 
Hello guys i am a new owner of this monitor and i am currently using strobe utility from the Blurbuster forums...I have already installed vertical tweak 1502 and set persistence at 1.5 but i cant find how to deal with Crosstalk..Some people suggest to set it completely left and some other to set it more to the right before it loses its brightness..Note i am using Blur reduction ON ..

Thanks in adnvance.
post #2 of 4
Did you use the pixel clock patcher before doing all of this? It must be installed (then you need to run the driver restarter, it is part of ToastyX CRU, so you can get the restarter from there, to avoid having to reboot PC after running the patcher).

http://www.monitortests.com/

And crosstalk is hard to explain.
The reason you have crosstalk is because of refresh.

Refresh rates is how many time the monitor refreshes a second
Monitors always refresh top to bottom. The refresh starts at the top and goes downwards. That is why the input lag (on any monitor review where they test input lag--like this one:

http://www.displaylag.com/benq-xl2720z-review-144hz-gaming-monitor/

(Go down to the input lag tests and you can see how top has lower input lag than the bottom, since the top refreshes first during a refresh sync).

How does this relate to crosstalk?
Well notice that you have the most crosstalk at the bottom of the screen?

Where is the input lag highest?
the bottom!
And that's where you have high crosstalk.
You can look for crosstalk on this test I recommend:

http://www.testufo.com/#test=photo&photo=alien-invasion.png&pps=960&pursuit=0&height=-1

press F11 to make it full screen.
The crosstalk is NOT the after image 'ghosting' of the UFO or red bar, with an inverted primary and secondary trail--that's just RTA/overdrive ghosting. The crosstalk is where you start seeing TWO frames jumbling together with a really super thick massive double/triple image...(and that's at the bottom).

The reason why this happens is because the same reason the input lag is highest at the bottom. The backlight shuts off and on every refresh (so at 120hz it shuts on and off 120 times a second). The problem is, at the bottom of the screen, since the input lag is highest, the bottom pixels have not finished completing updating the current frame before the strobe is done! So you actually have data from the *NEXT* frame mixed with the CURRENT frame. (next is key here). Actually, if the strobe phase is set to 000, you are actually having 1 frame of higher input lag than a high strobe phase.

As you increase the strobe phase, (you need to do this using the service menu; the windows slider utility is limited to strobe phase 047 to avoid shutting off the backlight), notice what happens.

service menu codes are here:

http://forums.blurbusters.com/viewtopic.php?f=2&t=2467

You start seeing a crosstalk field at the TOP of the screen move DOWNWARDS. Notice what you see above that crosstalk field and below it. Do you notice that the UFOs' and the vertical red bars seem to move AHEAD to the right one frame, ABOVE the crosstalk field, and "back" one frame below the crosstalk field? Since the image is moving from left to right, what you are seeing is the frame shifted 1 frame towards the destination -->the right--thus you are GAINING--improving input lag by 1 frame by raising the strobe phase!

So, to get the absolute lowest input lag, you must RAISE the strobe phase as high as possible before the backlight shuts off!

Now you might wonder "why..why do I have to do all of this?"

its just due to limitations with current monitor panels and response time of refreshing pixels. It's impossible to have NO crosstalk unless you have monitors with instant response time--CRT"s, Quantum LED's or OLED's.

So what exactly does strobe phase do ?
Simple.

it changes where DURING the refresh that the strobe starts and ends!
As you increase the strobe phase, you make the monitor start the strobe **SOONER** in the refresh. So you actually push the strobe phase into the PREVIOUS refresh -thus LOWERING your input lag--you gain 1 frame of improved input lag. This may not make much sense as to why you are pushing the strobe into the "previous" frame (which is actually the DESIRED CURRENT FRAME YOU WANT), until you realize that the default strobe phase is not 000. It's 100.

Now you might still be asking...."well....wait. Why is the default strobe phase set to 000 if it gives me 1 frame worse (higher) input lag?
Well...the default strobe phase is actually 100!!
When you flash a firmware or do a factory reset (recall all in the factory menu, or reset all, or set "Internet café" to enabled and turn off the monitor, it sets the strobe phase to 100. This gives you the lowest input lag possible, and you have absolutely NO crosstalk at the top of the screen. But because the BOTTOM of the screen has MORE INPUT LAG from panel response time than the refresh rate ITSELF (refresh rate frame lag is equal to 1000 divided by refresh rate in milliseconds)., you get a lot of crosstalk at the bottom of the screen.

Using a vertical total tweak causes the monitor to switch to 60hz backlight pulse widths, while 'extending' the blanking period of the strobe, which reduces strobe crosstalk, but also LIMITS the maximum strobe duty allowed--the higher the refresh rate (up to 128hz), the lower the maximum strobe duty. If you still want more information, and about WHY this happens I have math to explain it.

But here is a fun fact for you to think about in the meantime.

Maximum STROBE DUTY is 030. There are 30 values of persistence. Persistence is equal to the REFRESH RATE milliseconds divided by 100 --for example: 60hz is 16.7 milliseconds (1000 divided by 60), then divide 16.7 by 100 and you get .167, so each point of strobe duty at 60hz increases persistence (strobe width) by 0.167ms. (so without a VT tweak, the higher the refresh rate, the lower the persistence and the dimmer the screen).

Maximum strobe PHASE is 100. 100 values of strobe phase. All work perfectly.
At 120hz same thing. 8.3ms response time from refresh rate, 0.083 ms persistence per point of strobe duty.

But if you use a Vertical total tweak, 120hz uses the 60hz persistence values instead of the 120hz persistence values.
Maximum strobe PHASE then gets cut in HALF. Strobe phase 050 and higher turns off the backlight.

I'll let you think about that for a bit.
Edited by Falkentyne - 11/10/15 at 10:11am
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post #3 of 4
Thread Starter 
Wow...i am really impressed by your knowledge and ur answer..i really appreciate it...yes ive installed pixel cloak patcher but because i am playing cs go i was wondering if i have the best settings and especially about crosstalk..Generally u say that these are the optimal settings tha someone shoud use while playing cs go ?..i mean about 1.5ms peristence and late crosstalk just before it starts lose its brightness?
post #4 of 4
Yes, you are right.

I went into far more detail about strobe phase here.

http://forums.blurbusters.com/viewtopic.php?f=13&t=2540&start=10


From what I found out, the strobe phase description in the windows blur busters utility is actually wrong.
A strobe phase of 000 is actually a LATER Strobe phase--it strobes in the NEXT frame (thus you have 1 frame higher input lag) while a strobe phase at a high value strobes into the CURRENT frame (previous frame, relative to strobe phase 000) so this gives 1 frame improved input lag.
So yes, for CS:GO, you want to use the HIGHEST Strobe phase possible. But remember using VT tweaks is actually a firmware "exploit" and the monitor was not originally designed for this, so 60hz backlight pulse widths will *LIMIT* the maximum strobe phase setting (as I explained in the long link I posted).
Also a high strobe phase when using a VT tweak also limits the maximum strobe DUTY.

Example: 120hz, VT 1500 active.
050 strobe phase turns off the backlight (this is because the persistence drops to 0ms--the "OFF" period for the backlight is infinite and there is no "on" period)
049 strobe phase =this is equal to strobe duty 001 (higher values of strobe duty are ignored.
048 strobe phase =this is limited to strobe duty 002 (you can use duty 001 or 002 only).
047 strobe phase =this is limited to strobe duty 003 (you can use duty 001, 002 and 003 only)
And so on.

When not using a VT Tweak, all values of strobe duty work even at strobe phase 100 (But crosstalk is far too high at the bottom of the screen without a VT tweak).


This post has the limits of the strobe phase setting when the backlight is using the *60hz* pulse widths. (Any VT tweak causes the backlight to use the 60hz persistence pulse widths!)

http://forums.blurbusters.com/viewtopic.php?f=2&t=2467

So yes, adjust strobe phase as high as possible for LOWEST input lag and FASTEST response time in CS:GO. Once the backlight turns off, go lower and then keep decreasing it and increase strobe duty for every point you decrease strobe phase, until you get desired persistence and brightness.
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