4 ms·
> But I feel like we have a number of years to go until we can really get back to where we used to be with vintage gaming consoles and CRT displays. Interestin
by MayeulC 6y ago
> But I feel like we have a number of years to go until we can really get back to where we used to be with vintage gaming consoles and CRT displays.
Interesting. CRTs also had a fixed framerate. Let's make that 60 fps for the sake of the argument.
It really depends on what you are calling "vintage". Most later consoles (with GPUs) just composited images at a fixed frame-rate.
Earlier software renderers are quite interesting, though, in that they tend to "race the beam" and produce pixel data a few microseconds before it is displayed. Does that automatically transfer to low latency? I'm not sure. If the on-screen character is supposed to move by a few pixels with the last input, it really depends on whether you have drawn it already. Max latency is 16 ms, min is probably around 100 µs. That gives you 8 ms of expected latency. And I think you still get tearing, in some cases.
There is also no reason it couldn't be done with modern hardware, except the wire data format for HDMI/DP might need to be adjusted.
However, and I've said that for a long time, one key visible difference between CRTs and LCDs is persistence. Images on a LCD persist for a full frame, instead of letting your brain interpolate the images. The result is a distinctively blurry edge on moving objects. Some technologies such as backlight strobing (aka ULMB) aim to aleviate this (you likely need triple buffering to combine this with adaptative sync, which I haven't seen).
I wonder if rolling backlights could allow us to race the beam once again?
QLED/OLED displays could theoretically bring a better experience than CRTs if the display controller allowed it: every pixel emits its own light, so low persistence is achievable. You don't have a beam with fixed timings, so you could just update what's needed in time for displaying it.
- dan-robertson 6y agoA separate latency difference is in how long it takes for the pixels to switch. Ie the time between when the device starts trying to change the colour of a pixel and when you see that colour change. This is a relatively long time for an lcd but not so long for a crt
- MayeulC 6y agoWell, isn't it an aspect of persistence? This is usually called ghosting, and can be combated using "overdrive"; https://blurbusters.com/faq/oled-motion-blur/ https://blurbusters.com/faq/oled-motion-blur/ https://blurbusters.com/faq/lcd-overdrive-artifacts/ https://blurbusters.com/faq/lcd-overdrive-artifacts/ Edit: regarding my older comment, I thought that QLED were quantum dots mounted on individual LEDs. They are regular LCDs, with quantum dots providing the colour conversion. That makes more sense from an economical perspective, less so for performance. Maybe OLED and QLED could be combined to leverage the best OLED for all colors?
- dan-robertson 6y agoIf you draw a graph of the signal going into a monitor (above) vs the luminosity of a pixel, it might look like this for a crt: ^ | _______________ | / | | | | |_/ |_________________> t ^ | /\ | / \ | | \ | | \ | | `-._ |____/__________`-.___>t And the luminosity like this for an lcd: ^ | _________ | .’ | / | / | / |______-’______________>t Persistence is the time it takes between when the luminosity goes up and when it goes down. It is low for CRTs and high for LCDs (which stay on until they need to switch unless the monitor is low persistence (or low persistence is emulated with a high refresh rate and black frame insertion). The switching time is the time between when the signal starts (or rather when the monitor has finished working out what the signal means and has started trying to change the luminosity) and when it gets bright (or in the case of LCDs, to the right luminosity). Ghosting comes from not switching strongly enough and overdrive (switching too hard) tends to lead to poor colour accuracy.
- ric2b 6y agoThose charts are awesome, props for the creativity.
- MayeulC 6y agoNice charts, did you draw them by hand? You are right. That directly contributes to latency. This effect is called pixel response time [1], and is usually measured "grey-to-grey" [2]. Nowadays, though, I think monitors usually have a short response time (<1ms for "gamer" monitors). > Persistence is the time it takes between when the luminosity goes up and when it goes down Right. But that proves the two are somewhat linked, especially as pixel response isn't symmetric (0->1 and 1->0). Reading a bit more into it, the industry terms for persistence seem to be both grey-to-grey (GtG), and Moving Picture Response Time (MPRT). The latter is a measurement method [3] for perceived motion blur. It directly depends on the time each pixel remains lit with the same value ("persistence" strikes again), so a slow (>1 frame) or incomplete transition can create motion blur (contributes to persistence). > low persistence is emulated with a high refresh rate and black frame insertion It can also be achieved wit backlight strobing on backlit displays: strobing for 1ms on a "full-persistence" (pixel always on) display gives a 1ms persistence regardless of the frame rate. A ~1000 FPS display would be necessary to get the same level of persistence with black frame insertion alone. I believe this is part of the reason Valve went with an LCD instead of an OLED screen to get the 0.33ms persistence on the Index HMD. [1] https://blurbusters.com/gtg-versus-mprt-frequently-asked-questions-about-display-pixel-response/ https://blurbusters.com/gtg-versus-mprt-frequently-asked-que... [2] (from the above) https://hal.archives-ouvertes.fr/hal-00177263/document https://hal.archives-ouvertes.fr/hal-00177263/document [3] (also from blurbusters article) https://lcd.creol.ucf.edu/Publications/2017/JAP%20121-023108.pdf https://lcd.creol.ucf.edu/Publications/2017/JAP%20121-023108...