VT and input lag

[b0t]

is there a chance in this world that increasing vertical totals (1875 @ 144hz) adds input lag somehow? or am I having the worst placebo

[Chief Blur Buster]

is there a chance in this world that increasing vertical totals (1875 @ 144hz) adds input lag somehow? or am I having the worst placebo

Which sync technology are you using? You need to use RTSS (end-of-VBI pageflip) not VSYNC ON (beginning-of-VBI pageflip).

The use of Quick Frame Transport (aka QFT / large vertical totals / large VTs) requires concurrent optimization of your sync technology (can't use ordinary VSYNC OFF or VSYNC ON if you're wanting maximal input lag reduction with QFT signals). QFT has no effect on VSYNC OFF, and should ideally be used alongside other refresh-synchronous technology such as strobing or RTSS Scanline Sync or Special K Latent Sync.

[b0t]

is there a chance in this world that increasing vertical totals (1875 @ 144hz) adds input lag somehow? or am I having the worst placebo

Which sync technology are you using? You need to use RTSS (end-of-VBI pageflip) not VSYNC ON (beginning-of-VBI pageflip).

The use of Quick Frame Transport (aka QFT / large vertical totals / large VTs) requires concurrent optimization of your sync technology (can't use ordinary VSYNC OFF or VSYNC ON if you're wanting maximal input lag reduction with QFT signals). QFT has no effect on VSYNC OFF, and should ideally be used alongside other refresh-synchronous technology such as strobing or RTSS Scanline Sync or Special K Latent Sync.

Im using strobing (blur reduction on my benq XL2540 @ 144hz)
we've discussed it on my previous thread, u told me I can set it as high as 1875, I did. it didn't show any "no signal" or anything like it, I tested the vt 1875 with moving photo, crosstalk reduced alot especially at the bottom (my area is set to 15 which makes my "least clear" area of the screen the top.

I mean, if the display shows the resolution and the pc as before it means ive succeeded with raising the vt doesnt it? I really hope its a placebo.

tl;dr : Yes, I am using BenQ blur reduction enabled on my XL2540 @ 144hz

[Chief Blur Buster]

Great to know VT1875 helped. However, you didn’t answer my question — what sync technology are you using?

Large VTs can increase or decrease latency depending on what sync technology you configure.

Also, not all pixels refresh at the same time — the first to last pixels can refresh differently (high speed videos at www.blurbusters.com/scanout …) and the latency behaviours can change when time differential between first and last pixels change. Latency is never a signal number in the real world…

Sync technologies include things like VSYNC ON, VSYNC OFF, VRR/FreeSync/GSYNC, Fast Sync, RTSS Scanline Sync, Special K Latent Sync, etc. Sometimes uncapped VSYNC OFF is not the most ideal sync technology to use for certain kinds of display signals (e.g. strobed QFT).

[b0t]

Great to know VT1875 helped. However, you didn’t answer my question — what sync technology are you using?

Large VTs can increase or decrease latency depending on what sync technology you configure.

Also, not all pixels refresh at the same time — the first to last pixels can refresh differently (high speed videos at www.blurbusters.com/scanout …) and the latency behaviours can change when time differential between first and last pixels change. Latency is never a signal number in the real world…

Sync technologies include things like VSYNC ON, VSYNC OFF, VRR/FreeSync/GSYNC, Fast Sync, RTSS Scanline Sync, Special K Latent Sync, etc. Sometimes uncapped VSYNC OFF is not the most ideal sync technology to use for certain kinds of display signals (e.g. strobed QFT).

Oh I understand now, sorry.
Im using VSYNC OFF (for competitive play obviously), capped to 300 (but I might lower it because it does dip on full DM servers to about 160~ and can go up to 220~ish

so if VSYNC OFF + Large VT doesnt benefit me, you're saying I might aswell play on default 144hz strobed and that's it ?

EDIT : I've dug some stuff up from earlier threads that you replied to Mark ,

previous thread :
viewtopic.php?t=9807

you said "2.Reduction of input lag for refresh-synchoronized technologies such as DyAc strobing or VSYNC ON or anything that relies on refresh cycles being delivered fully (panel refreshes sooner = screen can strobe-flash sooner)"

and also another thread I've found asking about input lag in relation to fiddling with VT :

viewtopic.php?t=6558

and again, you wrote there :

Large Vertical Totals usually don't help VSYNC OFF (although it can helped strobed VSYNC OFF a little bit, because of the earlier flash). Non-strobed input lag is identical for VSYNC OFF non-QFT versus QFT, because the unsynchronized frame delivery all averages out. For a VT-double-visible-resolution, you may get half as much tearing though, because tearing will be hidden in the VBI half the time. (But if you're using non-strobed VSYNC OFF QFT at lower Hz, the pros mostly zero-out and the cons increase.... So you probably might as well use max-Hz anyway -- why are you reading this thread? Right Tool For The Right Job.... Non-strobed VSYNC OFF usually works best & feels best with max Hz).

I just need to know that there's ANY benefit for me using custom res @144hz VT1875 blur reduction ON vs just default 144hz blur reduction ON

EDIT#2 : By reading further into your replies in that post, and correct me if I am wrong ;

VSYNC OFF + strobing + QFT/Large VT like in my case, benefits the crosstalk more than the latency reduction, I actually am seeing improvement in the bottom rows of Alien Invasion in Moving Photo@UFO;

If I were to be more specific, I have the Area setting on 15, it means that if opening the test in fullscreen, lines 1-2 (from the top) and lines 14 [the bottom] (u may even say that in the 14th its slightly worse) but in the 15th line, crosstalk is severe. after enabling VT1845, it made lines 14-15 ALMOST as good as the 100% crosstalk free center (I'd say only by 15-20% worse than the center) , while on the top first,second and 3rd line this time - crosstalk became worse. now I can sacrifice another line from the top of my screen for almost 100% crosstalk free bottom.

but question is, doesnt it actually ADD input lag/latency somehow? considering Im not using any SYNC technology like u previously asked (only strobing+the 1875vt like I already said)


FINAL EDIT: just to be sure Ive done it correctly, I made it like Falkentyne taught back in the day:
1. Choosing LCD Standard ( was renamed to Automatic - PC) I guess?
2. Editing only the refresh rate to the desired one which is 144Hz
3. switching to Manual ticking the line to be able to set Vertical Totals
4. Making sure its set to :Porch 48,3 ; Sync 32,5 HT 2080 (AND NOT Porch 88,Sync 44 and HT 2200)
5. Setting the VT to desired value (which is for me 1875)

Here if I remember correctly (I'll check when I get to the PC to make sure) I got pixel clock of around 560mhz~ (using DP, supported up to 1.2 by my GTX970)

so did I do everything correctly? (read in the cru official thread that dp can actually go up to 600mhz or something)

[chandler]

really desperate for a reply here as I've been looking for a concrete answer about this for some time now all over the place (large VT vsync off + strobing input lag increase - apart from reducing crosstalk)

[Falkentyne]

You really need to test this for yourself.
If you don't feel any greater input lag, there isn't any. If you tell your brain there's input lag, your brain will create it for you.
Chief already answered this as best he can. The rest is up to you and your own testing. Sometimes you have to do the work yourself.

[progamingnoob]

I absolutely love the way high vt tweaks look when strobing, but it definitely at least feels like significantly more input lag, kovaaks scores fall of a cliff.

[b0t]

You really need to test this for yourself.
If you don't feel any greater input lag, there isn't any. If you tell your brain there's input lag, your brain will create it for you.
Chief already answered this as best he can. The rest is up to you and your own testing. Sometimes you have to do the work yourself.

Hi falkentyne, can you at least tell me if I've done it correctly ? (and if 560mhz clock via DP 1.2 is fine ? )

[Chief Blur Buster]

so if VSYNC OFF + Large VT doesnt benefit me

Only if you're not using strobing or a modified VSYNC ON

While there are monitor-specific exceptions, these are general rules of thumbs:

Things that benefit from QFT:
- Strobing with ANY sync technology
- Non-strobing with a modified VSYNC ON clone (e.g. RTSS Scanline Sync)

Things that do not benefit from QFT:
- Non-strobing with ordinary Microsoft Windows VSYNC ON (due to its beginning-of-VBI presentation behavior).\\

VSYNC OFF + strobing + QFT/Large VT like in my case, benefits the crosstalk more than the latency reduction, I actually am seeing improvement in the bottom rows of Alien Invasion in Moving Photo@UFO;

Correct.

but question is, doesnt it actually ADD input lag/latency somehow? considering Im not using any SYNC technology like u previously asked (only strobing+the 1875vt like I already said)

Since VSYNC OFF randomizes the splicing of the signal, average input lag of QFT vs non-QFT is identical. However, latency gradient does become slightly distorted. The input lag of top versus center versus bottom.

The interaction between signal scanout, display scanout, and global strobe flash, can distort the latency gradient (the lag difference of gametime:photontime for top edge of screen versus bottom edge of screen).

Non-QFT Version
Nonstrobed + VSYNC ON creates input lag gradient where top < center < bottom
Nonstrobed + VSYNC OFF creates identical lag gradient where top = center = bottom
Strobed + VSYNC ON creates identical input lag for top = center = bottom
Strobed + VSYNC OFF creates input lag gradient where top > center > bottom

Adding QFT simply tightens the latency gradient, where DIFFERENCE(top, bottom) is simply the time delta between delivery of first pixel row and delivery of last pixel row. However, in the case of VSYNC OFF, the AVERAGE of (top, center, bottom) is unchanged, even if DIFFERENCE(top, bottom) is a smaller lag difference, since top can increase a bit while bottom decrease a bit.

So yes, you are seeing modified latencies, depending on where your eyes are looking at (crosshairs? Top edge? Bottom edge?)

You may just simply have to get used to the new latency mechanics -- it is usually a matter of aimtraining to your new settings. You might have potentially noticed modified top-edge and bottom-edge latency despite unchanged center, or such -- it is a very odd latency gradient. lag at center -- it varies from screen to screen, and how its strobe backlight behaviour changes to large vertical totals. However, you might be used to years of a specific behaviour.