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 Post subject: Re: Measuring lag with the OSSC (LG OLEDs)
PostPosted: Tue Jan 07, 2020 11:35 pm 


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With 120Hz as an available option in some situations, I like knowing the total latency. Better testers will almost certainly arrive that test more signal types. The current "standard" is future proof.

Total display latency doesn't say anything about the game machine or software, but it let's us know what the possibilities are. Naturally, higher frame rates will lower the possible display lag "floor". I'm okay with latency numbers that show that (as long as the frame rate is mentioned).

If anything, I would like to see lag always presented with: the top, middle, and bottom readings AND the signal information ("resolution" and frame rate) AND the display settings during the test ("game mode" settings, etc., etc.) Few reviewers share all of that. It's also frustrating that nobody bothers to test deinterlacing lag. A Time Sleuth and five minutes isn't prohibitively expensive.

Showing me the total of processing latency plus "scan out" also tells me something about how the display works. Some displays completely buffer the frame before they begin a new "scan out". Also, I can make some generalisations about how a display's "black frame insertion" feature works with the lag numbers.

The real problem is: it's complicated and oversimplification will always confuse people in the end.

More and more often (it seems), there are multiple possible display latency numbers based on: signal type, frame rate, and display feature settings.
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 Post subject: Re: Measuring lag with the OSSC (LG OLEDs)
PostPosted: Wed Jan 08, 2020 12:36 am 


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I would have bet money someone would immediately pop up to say all that. :mrgreen:

Ok but personally before everything I like to tell about the one big misunderstanding that plagues like 90% of the cases that concern people playing video games and their displays, what they need to understand first is what the figures they read on the most popular websites actually mean so they can finally call things by their name.
If we start telling about all cases, mentioning also the soft's own delay etc ll at the same time, people won't follow the reasoning, they haven't for like a decade, so...
(you're right that with more and more 4K displays around it's important to explain the oddities some of those show, but basics/ basic cases first)

In any case strictly displays-speaking whatever the signal type/rate/scan fashion, I don't call what's part of the normal displaying process for a source 'lag' or 'delay', because it's not (which is why I don't use the misleading terms 'total display lag' anymore either) as clearly only what's abnormal/unwanted actually adding to the normal-ideal chain 'flow' within the display, deserves to be called lag/delay.

For your wish, oh I feel you. Honestly if I thought building a better database-type website for lag was any possible I'd have loved to participate. I have learned however, that it is almost impossible to convince stores to let me test displays, at least in my country it's dead.
As for gathering from ppl online you know it never brings much results, or it's already obsolete models, or contributors just drop a figure, no info whatsoever sometimes not even which bar, then they disappear...
One thing that would help change that to begin is an ultra cheap standalone tester, like 15~20 bucks max, because current options are all WAY too expensive. Naturally most don't see the interest of spending that money on something they'll prolly use only 2~3 times ever.
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 Post subject: Re: Measuring lag with the OSSC (LG OLEDs)
PostPosted: Fri Jan 10, 2020 11:42 pm 



Joined: 20 Oct 2016
Posts: 14
Xyga wrote:
The OSSC doesn't read-report like the other testers do, so when it apparently doesn't add the frame 'drawn' time wherever not-the-top you place the sensor, it tells only the actual lag/delay, and in most cases there is only one measurement to report.
(logically. tho that way of reading is too counter-intuitive for what ppl expect, I won't say it enough)



Not sure what your point is here - please elaborate.

Xyga wrote:

I don't dismiss any possibilities but xeos hasn't shared anything about his monitor besides the brand, still 4.3ms would be a very common result expected for tons of monitors today, that's what you'll read from a serious website like pcmonitors.info or tftcentral.co.uk, while lesser ones would give something around 10+ms taken from the middle of the screen or an average.
This case smells like it, like he read somewhere in a review/chart that his monitor is 10+ms, and now testing himself he's surprised to read less, same as Konsolkongen here.
The same happens often-enough with ppl using a LB or any other lag tester by themselves, like "wat this is less than x or y review said", and it's hard to swallow that much more popular websites like Rtings or displaylag are, well, not technically 'wrong' but slightly misunderstanding the topic of lag/delay.



Actually, nothing of the sort - no lag numbers have been published for my monitor, anywhere, as it's ancient, about 10 years old. KDL-40vl130. I figured before I upgraded I should see how much of an improvement I'd get. Anyway, no way it's doing 4.3ms. It might *possibly* be strobing the backlight, however, which could easily create a false positive for the probe onset. Indeed with more careful measuring I discovered that it sometimes returned the same nonsense <10ms measurement even when the sensor was not overlapping the probe, but was placed on the black part of the screen. If all decent monitors are < 10 ms then there's little point in this bit of DIY hardware modding, at least IM(H)O. nobody's ever going to be able to tell the difference between 0 lag and 10ms.


Xyga wrote:
In regards to what you think about the brightness/sensor, honestly I don't think it makes a big difference. Maybe like with the other testers we can read at worst a couple ms difference between 0% and 50% brightness then another two between 50% and 100%.
Like response times in most cases the difference brightness makes for lag testing shouldn't be any significant at all.


Reading an analog value like brightness with a fixed digital threshold is going to work well only if you are very lucky. Otherwise the threshold can be too low (like my case) or too high (resulting in no measurement at all). And depending on the empirical black-to-white transition curve it could add a lot to the lag. I did a simple modification to change the sensitivity on my setup - I covered part of the box holding the photodiode with an index card so that I could shift the trigger threshold (ie make the sensor less sensitive). This worked great to eliminate the false positives I was measuring below 10ms. Now by adjusting the light level reaching the diode I can measure lag levels of 20 ms to 54 ms. Doesn't matter where on the screen I make measurements - the effect of sensor sensitivity swamps screen painting time. This is why the wiki on the lag tester offhandedly mentions using a POT instead of a fixed resistor. Sadly when ordering components I didn't realize that the OSSC was using a binary threshold instead of a DAC, though in retrospect it's obvious that's what's going on, and of course a DAC would be crazy given that the circuit was designed for just reading a button press. Using a pot would allow a bit more control than my index card trick, but does not resolve the fundamental problem of measuring the analog value with a binary threshold.

Given my new understanding of the OSSC hardware I'm not so excited by the lag testing feature. I mean, it's certainly a neat hack and there's no harm to including it in the firmware. But it's far from robust enough to be worth much. Perhaps with OLED screens were the black to white transition is essentially instantaneous, and blacks really are blacks. But I assume all OLED screens have fantastically low lag, better even than the CRTs of legend.

No offense to the designer, marqs85, - he didn't set out to build a lag tester, and the OSSC is good for what it was designed to do.


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 Post subject: Re: Measuring lag with the OSSC (LG OLEDs)
PostPosted: Fri Jan 10, 2020 11:49 pm 



Joined: 20 Oct 2016
Posts: 14
Xyga wrote:
Think about it, by the logic of taking the center or average as the reference for measuring then all CRTs lag 8.3ms (at 60Hz)
That's just silly.


Yes and no. The real lag of a 120hz CRT is in fact lower than a 60hz CRT, and presumably that would only be empirically measurable if you choose somewhere other than the top of the screen to measure. Moving to the present, 120hz or 240hz screens are almost mainstream options now, though with a price premium to be sure. A fancy graph or table can convey the fixed lag and the lag due to refresh rate, but if you want a single value that captures what people actually experience center of the screen is probably the ideal.


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 Post subject: Re: Measuring lag with the OSSC (LG OLEDs)
PostPosted: Fri Jan 10, 2020 11:54 pm 



Joined: 20 Oct 2016
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Xyga wrote:
I would have bet money someone would immediately pop up to say all that. :mrgreen:

One thing that would help change that to begin is an ultra cheap standalone tester, like 15~20 bucks max, because current options are all WAY too expensive. Naturally most don't see the interest of spending that money on something they'll prolly use only 2~3 times ever.


After playing with a raspberry pi zero a bit for some home automation projects, I think $10 is doable. Certainly if you were willing to accept the binary threshold approach used by the OSSC. I'm not sure the pi can do faster than 60hz refresh over HDMI though. Disclaimer: I'm not actually working on a raspberry pi latency tester.


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 Post subject: Re: Measuring lag with the OSSC (LG OLEDs)
PostPosted: Sat Jan 11, 2020 9:28 am 



Joined: 19 Mar 2017
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According to an LG spokesperson they will know longer be disclosing input latency https://youtu.be/zRhd2Wsy6L0?t=344


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 Post subject: Re: Measuring lag with the OSSC (LG OLEDs)
PostPosted: Sun Jan 12, 2020 12:06 am 


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strayan wrote:
According to an LG spokesperson they will know longer be disclosing input latency https://youtu.be/zRhd2Wsy6L0?t=344
Perhaps they don't want to disclose input latency on newer models because they can imply by omission it's the same moving forward as it was for the best performing model.

My first question is this, are there appreciable gains to be had if 144Hz or 240Hz OLEDs become a thing?

60Hz = 16.67 ms/Frame
120Hz = 8.33 ms/Frame (-8.33ms vs. 60Hz)
144Hz = 6.94 ms/Frame (-9.72ms vs. 60Hz)(-1.39ms vs.120Hz)
240Hz = 4.17 ms/Frame (-12.5ms vs. 60Hz)(-4.17ms vs.120Hz)(-2.78ms vs.144Hz)

Not everyone buying an LG OLED is a console gamer. Anyone who tries a 60Hz vs 120Hz monitor can feel and see the 8ms difference (especially when using a mouse). However, the difference between 120Hz, 144Hz, and 240Hz may not be so easily discerned. There is only 1-4ms difference between them. On paper, the jump from 120Hz to 240Hz should only be half as dramatic as the jump from 60Hz to 120Hz. I've never actually tried it. So is it? And how much of the difference do you think is due to display tech (IPS vs LCD vs LED vs OLED, pixel refresh rate and such)?

Sure, psychologically gamers care about the extra 4ms, even if it they couldn't feel it (and I'm not saying they can't). A 1ms display removes the lag excuse for why you suck, which is reassuring when your putting in the time to not suck (it's one of the reasons I prefer retro games on CRT). On the industry side, playing up the importance of those precious milliseconds sells monitors. Everything else being equal, if one PC monitor didn't have input latency listed, would you buy it or the one that says 1ms? Even if they both were 1ms displays, you would buy the one that say's so for reassurance. So I get why it's importance might become inflated.

My second question is if the gains would be worth the additional cable bandwidth and GPU horsepower required to handle 240Hz for anything beyond 1080p? Is 120Hz the sweet spot? Perhaps that's where LG decision to stop making light of input latency is coming from. It's good enough to not really matter anymore.


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 Post subject: Re: Measuring lag with the OSSC (LG OLEDs)
PostPosted: Sun Jan 12, 2020 12:58 am 


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I worry that a push for higher frame rates will introduce more checkerboard rendering and all the artifacts that come with it to PC--where compression doesn't belong.

It's like pushing PC games to follow broadcast television down the interlacing rabbit hole.

If I have to give up proper rendering for high frame rates, I'm good with 60Hz and 1ms polling. If the games are coded well and you have a good display, the lag is sufficiently low.
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 Post subject: Re: Measuring lag with the OSSC (LG OLEDs)
PostPosted: Sun Jan 12, 2020 10:30 am 


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strayan wrote:
According to an LG spokesperson they will know longer be disclosing input latency https://youtu.be/zRhd2Wsy6L0?t=344


Have they ever listed inputlag on their TVs? Have any manufacturer ever done that? I can’t remember ever seeing this listed when looking at specs.


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 Post subject: Re: Measuring lag with the OSSC (LG OLEDs)
PostPosted: Sun Jan 12, 2020 6:57 pm 



Joined: 07 Jan 2017
Posts: 130
Konsolkongen wrote:
strayan wrote:
According to an LG spokesperson they will know longer be disclosing input latency https://youtu.be/zRhd2Wsy6L0?t=344


Have they ever listed inputlag on their TVs? Have any manufacturer ever done that? I can’t remember ever seeing this listed when looking at specs.

GAMING MONITORS :mrgreen:


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 Post subject: Re: Measuring lag with the OSSC (LG OLEDs)
PostPosted: Sun Jan 12, 2020 11:31 pm 


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You're probably right and that's what he meant, but he is being interviewed about their 2020 OLED TVs which is why it didn't make sense to me :)


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