XL2411P Flickering or turning off entirely with veritcal total of 1350 or 1502

Adjusting BENQ Blur Reduction and DyAc (Dynamic Acceleration) including Blur Busters Strobe Utility. Supports most BenQ/Zowie Z-Series monitors (XL2411, XL2420, XL2720, XL2735, XL2540, XL2546)
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Jimbo
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XL2411P Flickering or turning off entirely with veritcal total of 1350 or 1502

Post by Jimbo » 15 Mar 2021, 23:33

I don't know if my monitor is defective or not, but doing vertical total tweaks seems to be causing me issues after awhile. On 1350, I get some pretty noticeable lines across my monitor. On 1502, my screen would flicker. On 1500, my monitor would turn off and I would have to restart the PC. I am doing these tweaks on 120hz

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Chief Blur Buster
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Re: XL2411P Flickering or turning off entirely with veritcal total of 1350 or 1502

Post by Chief Blur Buster » 17 Mar 2021, 00:54

TL;DR: VT1502 is an overclocked Large Vertical Total
Jimbo wrote:
15 Mar 2021, 23:33
I don't know if my monitor is defective or not, but doing vertical total tweaks seems to be causing me issues after awhile. On 1350, I get some pretty noticeable lines across my monitor. On 1502, my screen would flicker. On 1500, my monitor would turn off and I would have to restart the PC. I am doing these tweaks on 120hz
VT1350 is a non-overclocked Vertical Total, but can also create lines similar to 144Hz strobed, because VT1350 is pushing your 120Hz refresh cycle into a 1/144sec scanout (144Hz), so only VT1350 is in-spec, but it will produce a lines-effect not too different from running the panel at native 144Hz strobed (that's an inversion artifact from a strobing interaction, very common on these 144Hz panels when strobed at 1/144sec scanout).

VT1500 is an overclocked Vertical Total for 120Hz -- it forces a panel into an overclocked 1/160sec scanout (aka 160Hz refresh cycle equivalent). Your refresh cycle is in velocity of 1080/1502ths of 1/120sec = approximately 1/160sec scanout. So no, it's not defective, you're just overclocking your LCD beyond spec.

Scanout velocity of an LCD is (vertical resolution)/(large VT) * (interval between refresh cycle). That's the time interval between first pixel and last pixel refreshed. You're creating a faster-scanout with a longer-idle between refresh cycle scanouts. Not all pixels refresh at the same time on an LCD, they refresh first to last pixel in a finite time -- high speed videos of scanout. Large Vertical totals speed up the scanout, and sometimes the scanout is beyond manufacturer spec (e.g. scanout faster than 1/144sec even though interval between scanouts is lower than 144).

To make Overclocked Vertical Totals more reliable on your XL2411P, you will need to use a utility such as OORbuster (Chopper1337 fork specific to XL2411P) found in the 220Hz overclock thread. Then you can do really humongous VT's (possibly VT1800 or VT2000).

You do want to derive your large-VT mode from an existing working mode though (ideally), via the clone-working-overclock, then lock-radio-button-on "Total" AND "Pixel Clock" (in ToastyX), then increasing Vertical Total (which will automatically lower your refresh rate when you manually increase VT). So if you had a successfully working VT1125 200Hz mode, you may be able to get a (VT1125 * 200 / 120) = VT1875 at 120Hz, if you manually modify a working overclock (rather than doing an automatic / GTF / CVT formula).
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Falkentyne
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Re: XL2411P Flickering or turning off entirely with veritcal total of 1350 or 1502

Post by Falkentyne » 17 Mar 2021, 02:43

Just to check a few things,

What timings are you using for 120hz?
Make sure you are NOT using the 60hz porch / sync / horizontal timings! That will set your horizontal total to 2200, which can cause issues due to a way too high pixel clock (This leads to a 396 mhz pixel clock).

For example:
Porch: 88,4
Sync: 44,5
HT: 2200
VT: 1500

Leads to a 396mhz pixel clock.
I've had issues with this timing before.


Porch 48,3
Sync 32,5
HT: 2080
VT: 1500
Leads to a 374 mhz pixel clock.
This one works.

You can also try HT: 2001, VT 1497-1498-1499. This will keep your pixel clock below 360 mhz, which will keep your monitor at 8 bit color depth. (some monitors will drop down to 6 bit color or YCBCR422 mode if you go above 359.9 mhz).

*NOTE* when using HT: 2001 and VT 1497-1499 please check carefully for frame skipping / pulsating backlight due to a failed sync. You can check for this in Test UFO/Alien invasion fullscreen with blur reduction enabled. Certain VT/ HT combos cause frameskipping! This is an issue on the Mstar scaler monitors. Certain exact HT/VT combos may cause frameskipping "sometimes" when you switch modes (or activate the S-switch or a monitor preset display mode). Certain HT/VT combos cause frameskipping all the time. Certain combos are 100% reliable. I found 100hz to be very tolerant of everything on the Mstar monitors, but 120hz was rather picky about what was reliable, and 85hz was even MORE picky (everything frameskipped in the VT 1497-1502 range *EXCEPT* VT 1501 ).

Jimbo
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Re: XL2411P Flickering or turning off entirely with veritcal total of 1350 or 1502

Post by Jimbo » 17 Mar 2021, 18:07

The only thing I've touched in timings was the vertical total, I never thought to touch the porch or sync numbers. I was simply following a guide to get the most out of my monitor, and it told me to turn on blur reduction and to create a custom resolution at 120hz with a vertical total of 1350. While I was pleased with the motion clarity, I wasn't sure why I had lines across my monitor until Chief posted his explanation.

So Falken, is my goal here to stay below a certain pixel clock? Even at 120hz, with default porch, sync, HT, but a 1500 VT will still result in problems with my monitor(374.4 mhz pixel clock). I have tried 100hz with a 1502 VT and have absolutely no issues. Should I push the VT even higher at 100hz? I'm not sure where to go, I'm simply trying to make the most out of my monitor and am with all this information.

Falkentyne
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Joined: 26 Mar 2014, 07:23

Re: XL2411P Flickering or turning off entirely with veritcal total of 1350 or 1502

Post by Falkentyne » 18 Mar 2021, 00:24

Jimbo wrote:
17 Mar 2021, 18:07
The only thing I've touched in timings was the vertical total, I never thought to touch the porch or sync numbers. I was simply following a guide to get the most out of my monitor, and it told me to turn on blur reduction and to create a custom resolution at 120hz with a vertical total of 1350. While I was pleased with the motion clarity, I wasn't sure why I had lines across my monitor until Chief posted his explanation.

So Falken, is my goal here to stay below a certain pixel clock? Even at 120hz, with default porch, sync, HT, but a 1500 VT will still result in problems with my monitor(374.4 mhz pixel clock). I have tried 100hz with a 1502 VT and have absolutely no issues. Should I push the VT even higher at 100hz? I'm not sure where to go, I'm simply trying to make the most out of my monitor and am with all this information.
Hi,
On the Mstar scaler models, touching only the vertical total is a mistake.
If you edit the 60hz values, you will notice that the front porch is 88 pixels 4 lines and sync is 44,5, and HT is 2200.
if you apply this to another refresh rate, trying to do a tweak, since the HT is so high (2200 vs 2080), this can cause issues. I saw no problem at 100hz, but there were issues back when I used DVI, trying this at 120hz on my XL2720Z. I assume there may also be issues with displayport as well.

When I switched to the lower values (select "Automatic" in Toasty X CRU, then I switch to manual later) for 100hz and 120hz, which reduces the front porch to 48,3 and sync width to 32,5 and HT to 2080, this worked fine at both 100hz and 120hz.

There was no problem with DVI as long as you used the "Toasty X Pixel clock patcher".

The only issue was, over displayport, going above 359 mhz would switch the card into 6 BPC mode due to the 360 mhz pixel clock limit for displayport 1.1. I believe on Nvidia cards it might fall back to YCBCR422 mode (I am unfamiliar with this mode, but I've seen it used with HDMI). Does weird stuff to the colors...

So for 120hz, what I did on my XL2720Z (over displayport) was reduce the horizontal total manually even below the "2001" value I mentioned (with a VT of 1498). (because of random issues with pixel skipping on some mode switches). This worked GREAT on an AMD video card, but on Nvidia it was VERY unreliable. So I found some settings which worked perfect on Nvidia:

1920x1080@120: (Nvidia)
Porch 24,3
Sync 32,5
HT: 1984
VT: 1500
Pixel clock: 357.12 mhz

With these timings, 120hz is perfect and NEVER randomly pixel skips or "backlight pulses" after a mode switch/resolution switch.

You can try this.

For AMD I used:
Porch 48,3
Sync 32,5
HT: 2001
VT:1499 or 1497 (I forgot).

Perhaps the nvidia one is also reliable on AMD too.


For 100hz, just use
porch 48,3
Sync: 32,5
HT: 2080
VT: 1500.

Jimbo
Posts: 4
Joined: 15 Mar 2021, 23:25

Re: XL2411P Flickering or turning off entirely with veritcal total of 1350 or 1502

Post by Jimbo » 18 Mar 2021, 03:16

Thanks for the explanations, Falken. I ended up trying your settings

1920x1080@120: (Nvidia)
Porch 24,3
Sync 32,5
HT: 1984
VT: 1500
Pixel clock: 357.12 mhz

And I no longer have any issues. Seriously, thank you. Appreciate it.

Falkentyne
Posts: 2793
Joined: 26 Mar 2014, 07:23

Re: XL2411P Flickering or turning off entirely with veritcal total of 1350 or 1502

Post by Falkentyne » 18 Mar 2021, 16:50

Jimbo wrote:
18 Mar 2021, 03:16
Thanks for the explanations, Falken. I ended up trying your settings

1920x1080@120: (Nvidia)
Porch 24,3
Sync 32,5
HT: 1984
VT: 1500
Pixel clock: 357.12 mhz

And I no longer have any issues. Seriously, thank you. Appreciate it.
Glad to help.

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