Does TN monitor color dithering add input lag?

[Throckmorton]

We know that when monitors do scaling and visual "enhancements" it takes extra time for the image to actually get to the screen, aka input lag. This is why monitors without built in scalers and other hardware between the input and display can have less input lag.

But what about dithering? TN monitors are supposed to have low response times and therefore be better for gaming, but EVERY TN screen dithers to get from 262,144 colors up to "16.2 million" colors. I would think this would require a lot of processing and therefore add a lot of input lag.

 

[Throckmorton]

No comments after 4 days??

 

[NoQuarter]

I don't know. But I have seen that while IPS panels on average have worse input lag than TN panels, the fastest IPS panels have less input lag than the fastest TN panels. Is that because of the dithering TN panels have to do? I don't know!

Maybe someone at beyond3d knows more.

 

[LtGoonRush]

I'm not certain, but I believe the answer is no, because like LCD overdrive the temporal dithering operates on the electrical signal being sent to the LCD transistors, not the image data.

 

[Ross Ridge]

Dithering is very easy to do, and can be done without having buffer an entire frame at once. There wouldn't need to be more than a couple of lines of lag.

Stuff the causes the huge lag you see on TVs is largely because the processing being done needs to have two or more entire frames buffered to work.

 

[Throckmorton]

Dithering is very easy to do, and can be done without having buffer an entire frame at once. There wouldn't need to be more than a couple of lines of lag.

Stuff the causes the huge lag you see on TVs is largely because the processing being done needs to have two or more entire frames buffered to work.

But what about temporal dithering? The monitor has to figure out the next 2+ frames before it can display them, right?

 

[MathMan]

Temporal dithering in TN monitors doesn't require earlier frames: all it does is jiggle the LSB of the 6 bit pixel in a fixed way.

Eg given a constant picture and an 8 bit value of 9, the 6 bit value sent to the panel will be something like 2/2/3/2/2/2/3/2/...

Dithering is one of the easiest operations in the monitor pipeline and is usually done without looking at the surrounding pixels. Basically zero additional input lag.

(BTW: a common misconception is that overdrive adds significant lag. It doesn't. You only need to look up the earlier value and a lookup table, but that doesn't add lag to the current pixel.)

 

[Ben90]

But I have seen that while IPS panels on average have worse input lag than TN panels, the fastest IPS panels have less input lag than the fastest TN panels.

An oversimplified rule of thumb is that going to 120hz from 60hz cuts off 8.33ms of input delay with everything else being equal. Since the fastest 120hz panels already offer under 8ms of delay, its impossible for current 60hz IPS panel to be faster than these best TN's.