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Old 18 February 2019, 17:41   #1
Dr.Venom
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High Dynamic Range and Wide Color Range

Hi Toni,

Quick question on a possible improvement for black frame insertion. Currently black frame insertion is the only way to experience the smooth motion of a CRT on a LCD, but at the cost of much lowered brightness. (Too much IMO).

I was wondering whether it would be possible to use the beamracing method to insert a black frame only during a single frame slice, for example if we would have 10 slices, only insert a black frame on (during) slice 10.

Since there's very little jitter with the frame slicing and it's actually vsync-OFF (instant frame flipping), would it actually flip (show) an entire black image for the 1/N duration of a frame?*

Potentially this would result in much less "strobing" and much improved brightness, while retaining the smooth motion aspect(?).

Would love to hear your opinion on this.

* Edit: I assume this feature would only be possible with a G-Sync monitor.

Edit 2: On second thought this would probably need a 500Hz G-sync monitor for the 10 slices example. Hmm...

Last edited by Dr.Venom; 18 February 2019 at 17:51.
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Old 18 February 2019, 18:22   #2
Toni Wilen
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This is probably something that bright HDR capable display would fix.
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Old 25 February 2019, 14:52   #3
Dr.Venom
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Quote:
Originally Posted by Toni Wilen View Post
This is probably something that bright HDR capable display would fix.
It'll probably fix the darkness, but I'm not sure how the strobing will look like since the difference between bright and dark will become bigger. Maybe for this we would need 200Hz monitors, such that every fourth frame could be "black frame inserted", instead of every second?

With regards to HDR I noticed a page on MSDN that has some information / links for enabling HDR and WCG in applications (you probably already seen it):

High Dynamic Range and Wide Color Gamut

The page also has a nice example on the brightness of various objects. Never knew that the reflection of the sun on the metallic surface of a car is 10.000 nits. Not to speak of the sunlight reflecting in a car window: 300.000 nits!
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Old 25 February 2019, 19:02   #4
Toni Wilen
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Yeah, I have seen that page.

This is probably wrong thread but HDR implementation needs some discussion first because it does not seem to be that simple and use of HDR with emulators isn't very popular topic and normally source images are already in expected HDR format.

- How to properly convert Amiga output to HDR colorspace (R10G10B10A2 or R16G16B16A16). Linear conversion? Range? Or can it still use normal R8G8B8 and GPU does automatic conversion of target mode is HDR?
- https://developer.nvidia.com/hdr-gdc-2018 explains some things and also says float R16G16B16A16 should be used for best compatibility and quality.
- SetHDRMetaData(). Lots of parameters here..

And so on..

Of course this must be optional which means too deep display emulation changes are not possible. Real implementation won't happen until good enough gaming HDR monitor gets released. (I do have 4K HDR capable TV (and also projector) but using them for testing and development is too annoying)
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Old 03 March 2019, 14:30   #5
Dr.Venom
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Good points.

I guess most important thing to answer is why would we want HDR enabled for WinUAE?

From what I understand our CRTs from yesteryear - on which 99% of the Amiga library was developed - have a peak brightness of around 200 nits (this needs verification). Since LCDs these days are capable of the same peak brightness or better, it doesn't seem to make sense to have HDR implemented for plain "unfiltered" WinUAE usage.

Probably THE reason we would want HDR implemented is to create a step up for shader usage and then mainly CRT shader authenticity?

For example simulating a Trinitron CRT or Slotmask CRT faithfully, requires the application of scanlines and masks which lower the brightness by a substantial amount. Clearly for truly accurate simulation, without making use of tricks like "brightboost" in the shader etc, the peak brightness for any average LCD will get lowered (in some cases probably substantial) below 200 nits, giving rise to a more "dull" and/or unnatural looking image / CRT simulation.

Another question then is HOW would a shader want to compensate for loss of brightness because of scanline and mask application? Is it possible to target a certain peak brightness level after application of scanlines and masks? I.e. would it be possible for a shader to target a certain peak brightness like CRT values of 200 nits for complete authenticity?

I think input from guest.r on this topic would be very helpful.

As a small starting point I found that someone tried (and apparently succesfully) to enable HDR (and WCG?) for NVidia and make use of it through shader application in the Dolphin (Wii) emulator.

It clearly seems a hack, as there's a seperate utility to start / enable HDR mode system wide before running the emulator, but maybe it can spark some ideas. Both git repos can be found here:

HDR-switcher
HDR-shaders

Lastly I understand this discussion may come a bit early, since there don't seem to many WinUAE users out there that have HDR capable setups / workable test setups.

Anyway, it would be fine to rename this thread into something like "High Dynamic Range and Wide Color Range", and keep this as a starting point for some (future) discussion?
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Old 03 March 2019, 19:25   #6
Toni Wilen
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So far I have 3 reasons:

- CRT shaders.
- Black frame insertion
- Brightness/contrast/etc adjustments that support HDR if enabled. (Instead of clipping almost immediately)

There is lots of time to plan this properly
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Old 03 March 2019, 23:51   #7
Foebane
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I had to research Black Frame Insertion to see what Dr.Venom was even talking about, and after the explanation and seeing this demo, I can see that it would be closer to recreating a CRT display, but would be darker, although to me, the BFI'ed UFO looked as bright as the blurry UFO. My monitor is running at 50Hz max, so wouldn't be much use for BFI. And yes, Amiga emulation looks smooth but blurry on it.

I'd also like to link to these videos explaining why trying to recreate a true CRT display on an LCD monitor is nigh-on impossible to do authentically, and (I guess) would require much more processing time than the emulation itself:
Original: [ Show youtube player ]
Follow-up: [ Show youtube player ]
This channel is well-worth a look, too.
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Old 04 March 2019, 19:04   #8
Toni Wilen
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I don't think these videos are on topic. This is about HDR/wide color, not some CRT or LCD basics.
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Old 04 March 2019, 22:13   #9
Foebane
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Quote:
Originally Posted by Toni Wilen View Post
I don't think these videos are on topic. This is about HDR/wide color, not some CRT or LCD basics.
Sorry, I thought this thread mentioned custom overlays and filters for the recreation of such displays. They could be useful in that regard.
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