Having trouble explaining why tv's cause lag to gamers.

Do you really need an analogy like that? I find that analogies actually tend to complicate matters, rather than make things easier to understand. I understand exactly what the problem is, and I don't understand your analogy at all.


All you need to do is explain that CRTs were analogue displays that basically displayed an image instantly via a simple electrical connection.
Modern displays need to process the image before it can be displayed, and this introduces a delay. The length of the delay depends on the display and the amount of processing being done.

The delay usually doesn't matter for watching video - though it can cause lip-sync problems if there is not an equal delay applied to the audio - but is a big problem with games because you have to react to things happening on-screen, and you expect the game to react to your inputs immediately, rather than being shown a delayed image.


P.S. Please don't use colored text. Not everyone is using the default theme, and blue on black is hard to read.

Any delay impacts gameplay, whether it's below 17ms or not. (assuming 60fps)

I'm not sure what's hard to understand when you say that a CRT has no delay because it's an analogue display and the signal is essentially a direct electrical connection requiring no processing, therefore there was no delay.

Flat panels require the image to be processed before it can be displayed, which adds a delay. The length of the delay can vary depending on the type or amount of processing being done.


Making it into an analogy only serves to complicate matters, and if you're wanting a basic explanation, there's no need for anything more than that.

Answer: because flat panels need to process the image before it can be displayed, which takes time, and different models of TV can have different delays depending on the type or amount of processing applied.


Talking about frames just complicates matters, and frames aren't all that relevant - delays are in milliseconds, not frames.
For a gamer, you may want to divide that by ~17 (1/60) to calculate how many frames of delay there are but as I said, it just complicates things. ~17 assumes the game is 60fps, rather than 30fps (console) or 120 fps. (high-end PC)

For example, 40ms delay would be two frames at 30fps, three frames at 60fps, and five frames at 120fps, because you must always round up when counting frames.

Or if you had two displays, one with a 1ms delay, and one with a 7ms delay, even at 120fps (8.33..ms per frame) the 1ms display would still be faster, though both technically have a zero frame delay.
If you simply explain that there's a fixed time delay, I'm not sure why someone would think that there could be a backlog that builds up. If you start talking about frames etc. then it complicates matters and perhaps someone could think that.

Lag can exceed the time between frames.

Lag can be as long as it takes for the first frame to appear once input is received.

To take your carwash analogy (which you want to replace by the way). "How long is the carwash?"

On a CRT, you opened your garage and started driving. No lag.

On a spiffy LCD, you opened your garage, some people buffed the car, then you started driving.

The "buffing" is your measure of lag.

The reason the car wash analogy is bad is that it doesn't really help show why the next frame is delayed.

Maybe plumbing?

In the old days, the water supply was on a short pipe under the sink. Turn it on, the water flowed. You could use each drop immediately.

Now, due to nasty stuff in the water supply, we need to purify each and every drop. We turn it on, each drop gets UV, reverse osmosis, filtering. Then we get it. Each drop gets these processes. so each drop is delayed before we can use it.

The problem for gaming (and again the analogy sucks), is we need to react to each "frame" quickly -- as Chron says -- because the next drop is wriggling out before we've even seen the previous one. And it's "programmed" to be hot, cold, whatever. We might know something about it based on how hot or cold the previous drop is, but we haven't even seen the previous drop.

But, again, the processing time could be 100 drops (or frames) long. It's simply not true that lag cannot exceed time between frames (drops). Sure, any TV or monitor that did would suck for gaming (or really for video), but it would very, very much be possible TGM. And I think your problem with the question stems from a misapprehension of that fact.

The "pipeline", the "carwash", whatever, is entirely independent of the frame length. That pipeline is "lag". It could be a partial frame or many frames long. So long as it can hold all the frames as "work in progress", it won't lose any of them. A factory does this with ease. It might have the capability of producing 60 cars per hour (frames per hour, i.e time between "frames" = one minute), but take 30 minutes to produce a single car ("lag" of 30 minutes because a car needs welding, parts being put in, painting, etc.). We can see that this is like having lag that is 30x the frame rate. This would suck for a first-person shooter. But it's probably really good for an auto plant. Oh, and before you say, "That's not realistic". There are absolutely auto plants that can mange 60 cars per hour (about 1200 per day, >300K per year assuming multiple shifts, but at least one shutdown day per week). There's a plant like that not from from me, although it's current only configured for 20,000 cars per year because it was sold by Toyota to Tesla. Now, I'm guessing that the "lag" is actually far longer than 30 minutes because I suspect there is no car on earth assembled that quickly, but if anything, that just enhances the point, doesn't it?

Gamers might need an analogy to help them understand propagation delay for an image. But, what they really want to know is can displays be designed to drastically reduce propagation delay.

I realize it’s caused by an apparatus and not propagation time of a cable, but a delay time is still perceived the same.

Would UHD up scaling due to lack of native content increase lag due to image processing? Are the array processors used for image processing more powerful to compensate for the increased pixel count?

TGM, I gave you a visualization.

I didn't intend to imply you don't understand the problem, but I'm not sure how these people have concocted such a stupid false equivalency that it's required.

Regardless, I gave you a solution.

And this, quite frankly is moronic: Where are they "used to" this from?

What they should be "used to" is "frame 1 comes in", it goes down the assembly line... later, frame 2 comes in... frame 1 is far enough down the line that frame 2 is at Station A... frame 3 comes in... Frame 1 is at Station C.. Frame 2 is at Station B... Frame 3 is at Station B.... Frame 4 comes in... Frame 1 exist... Frame 2 goes to station C.... Frame 3 goes to Station B... Frame 4 goes to Station A...

Lag = A + B + C.... 3 frames...

Anyone who can't understand this is too dumb to be wasting your time on. I'm sorry.

It shouldn't, if manufacturers actually care to put in a decent game mode. 4K is exactly 9x 720p or 4x 1080p and nearest neighbour resampling would give you the appearance of a 1:1 mapped image. (but with less pixel structure)
I agree. The concept of having a buffer to collect frames for processing (i.e. queuing) shouldn't be that hard to get your head around.

If it's a 60Hz display, and it takes 150ms (9 frames) to process the image, then the display will have enough memory to store 10 frames. (9 plus the one it's currently working on)

This is really weird.

If you are designing a game mode, you want the fastest processing possible to reduce lag - nearest neighbour is as fast as you can get.
Because 4K is exactly 9x 720p, and exactly 4x 1080p, you can use it without introducing any artifacts into the image - it will look the same as it would on a 1280x720 or 1920x1080 native display.

You can't do that with today's displays because they are either 1366x768 or 1920x1080 native, so 720p doesn't scale nicely. 1080p can be 1:1 mapped on a 1920x1080 display. You just increase the size of the pixels so that a 720p pixel is now a 3x3 square on a 4K display, and a 1080p pixel is now a 2x2 square.

With games, you are actually much better off using nearest neighbour resampling if you can. Using anything more "advanced" than that blurs the image. It's different when you are dealing with the perfectly anti-aliased, much softer images that you get with filmed content - but even then I would prefer the option of being able to use nearest neighbour resampling.

To dispel the backlog idea here, you could emphasize that frame 2 is still 16.66ms behind frame 1 (simultaneous processing - not buffering) so everything just comes out 83.33ms later. This never explained to me how some 60hz (16ms) lcds used to have > 80ms response times (a pixel can't have simultaneous values). The color reproduction must have been terrible.

Some people think upscaling is detrimental to image quality, and much of the 4K image scaling we've seen so far also includes image sharpening in their algorithms. Nearest neighbour allows the image to look exactly the same as it did on a 1080p native display, but without the pixel grid over the image, due to the increased pixel density. E.g. 1080p native display, 4K native display. (note: examples are actually photographs of iPads with & without a retina display, but it would be the same)

If you are using more advanced interpolation, hard-edged parts of the image are softened and can be more difficult to read.
For video content, I would definitely be wanting to use good edge-adaptive interpolation, but not for games, where the appearance of a 1:1 mapped image is far better.

And for the sake of comparison, here's that same image scaled 3x with:

• Nearest Neighbour
• Bilinear
• Jinc

I would say that example was a good candidate for an edge-adaptive algorithm like Jinc, but Jinc scaling is probably better than most displays are using. The image definitely appears softer when using it as well.

They sound dumb.

This "deceptively simple" world they come from is irrelevant to the question, "How can lag be greater than the time between frames?"

I don't have any interest in rehashing the past of low-frame-rate FPS games (although it might be instructive in how they developed such a completely irrelevant worldview).

The "car wash analogy" explains perfectly how lag can be 10000000000000000 frames long. I believe I could explain this to a 5-year-old. I am confident I could explain it to a Best Buy employee.

So I have no idea what they are "intuiting" here because it really doesn't make any sense at all. What possible logic would their be to intuit, "You can't have lag higher than time between frames without dropping frames?" Why wouldn't you intuit, "We'll hold onto the frames somewhere."

I mean there apparently is software development going on here and this concept is hard to grasp?

To me, that's impossible to grasp.

Lanczos has too much ringing and aliasing.

• Lanczos 3
• Lanczos 3 Anti-Ring

Jinc's benefits are more obvious in other images though, I'm only using that one because there are also photographs that illustrate how Nearest Neighbour looks on actual displays.

A bucket brigade is a simple analogy or visualization of delay caused by a process.

There are fifty men standing in a line. Someone hands the first man a bucket full of water, and he hands it to the next man in the line. Someone hands the first man another bucket full of water, while the second man is passing his bucket to the third man in line. The first man passes his bucket to the second man, and the second man passes his bucket to the third man and the third man to the fourth man.
The bucket passing process continues, but it takes time to pass each bucket to the next.

We have the summation of the time it takes to pass a bucket for each of the fifty men for the first bucket passed to reach the end of the line. After the first bucket reaches the end of the line, it only takes the time to pass one bucket to receive the next bucket at the end of the line.

Throughput can be increased by adding lines of fifty men. Given a second line of fifty men there will be twice as many buckets processed. But the time it takes for an individual bucket to reach the end of the line is still the summation of time of bucket passes.

I don’t know the context of the presentation but a video of a Rube Goldberg like contraption would be fun to show an apparatus being loaded and the delay of arrival at the output, but lower time for subsequent arrivals oncethe process path is loaded.

madVR