Guest-Advanced 4k HDR1000 experiments

RetroArch Additions Shaders
#1

Intro:

Here are the results of my recent experiments to optimize guest-advanced for 4k HDR1000 displays and 100% masks.

I adjusted the scanline beam profile to maximize the dynamic range, avoiding clipping of course.

Quite a bit of time was spent playing with sharpness controls. RGB sharpness is optimized, but NTSC sharpness can be adjusted to taste. I would avoid messing with the horizontal filter too much, though. “Horizontal Blur Sigma” can be increased up to 0.80 for more sharpness/ringing.

Mask 10 is the default, scroll down to “Recommended Mask Settings” for other mask settings.

I have omitted any combinations which resulted in low brightness, or which are not designed to work the display’s subpixels.

Any feedback or suggestions for improvement are welcome!

Observations:

Even at 1000 nits, I found some mask/scanline combos to be too dark. In fact, most slotmask combos still leave something to be desired. 4k HDR1000 is not the endgame for CRT emulation. There are still limitations with masks and scaling at 4k, and HDR1000 is not sufficient for all mask/scanline combos. At 8k, all of the mask/scaling issues should be resolved. HDR1400 is currently the highest tier of HDR brightness, which may be enough for all slotmask combos (does anyone have an HDR1400 display around here?).

Instructions:

-HDR1000 and 4k are required

-Recommended HDR settings for HDR1000 displays: Luminance 1000, Paper White 1000, Contrast 5.0. This may need to be adjusted based on your display.

-Local dimming should be disabled

-These have been tested at 10x scale with overscale - they should work pretty well at 9x and other scales, but I haven’t tested them thoroughly at other scales.

TVL and Brightness:

Preset:		TVL:	Brightness:
dotmask		432		Medium 
MGX+slot	720		Medium
RGBX		540		Medium
MGX			720		High
RRGGBBX		308		High

Download: https://mega.nz/file/A6sFFJrQ#mqm5AGEOSmFGELncCH2yE7aFOEHTbRfpWOSxJRuoaf4

Photos:

Recommended Mask Settings:

Mask Type Pattern Approx. TVL
RRGGBBX 12 ~308 TVL
RGBX 10 ~540 TVL
MGX 9 ~720 TVL

Slotmask can be added to any mask by setting “Slot Mask Strength Bright Pixels” and “Slot Mask Strength Dark Pixels” to 1.00. You may need to adjust “Slot Mask Height” to either 2.00 or 3.00 depending on the scale that’s being used to avoid moire-like interactions between the mask and scanlines. Warning! Slot mask can make the image too dim even on an HDR1000 display.

A note on sharpness:

For low TVL masks like RRGGBBX, different sharpness settings are required. I recommend the following as a starting point.

ntsc_ring = "0.000000"
ntsc_sharp = "-10.000000"
ntsc_shape = "0.500000"
NDEBLUR = "8.000000"
DEDGE = "0.700000"
GAMMA_INPUT = "2.400000"
gamma_out = "2.200001"
HSHARPNESS = "1.000000"
SIGMA_HOR = "0.700000"
S_SHARP = "0.000000"
HSHARP = "1.000000"
MAXS = "0.300000"

Update 9/26:

-Replaced rgb presets with new presets using the ntsc version of the shader, tweaked for perfect sharpness/color/etc. The additional bit of processing looks better than the regular version of the shader- it’s actually capable of being a bit sharper with lower TVL masks.

-Spent quite a bit of time tweaking the horizontal filter- this should be the safe maximum for sharpness. Let me know what you think- best judged with a high TVL mask like MGX.

-Gamma corrected (standard 2.5/2.2) - helped color separation in highlights and improves the colors

-Adjusted beam profile accordingly. Try increasing Scanline Shape Bright Pixels and you’ll start clipping almost immediately. Try reducing it and the scanlines disappear over the brightest colors. Adjusted the dark beam as well to compensate for gamma adjustment.

-Added slight vertical deconvergence- I think it improves shade separation in highlights, lets you eek out a bit more brightness. Basically just gives you a bit more scanline variability. Plus, it looks good :slight_smile:

Update 10/21:

Reduced presets, added instructions for mask settings- minimizes the number of presets, and I like keeping things simple.

A few tweaks to gamma, brightness boosts, etc

Added magic glow 0.02 - I think it helps mimic more realistic phosphor behavior

Minor tweaks to sharpness

Added a new mode, “Enhanced S-video,” featuring “smart dithering deblur.” Basically the cleanest possible image with separate Y/C. Thanks, @guest.r!

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Guest-advanced-ntsc: Final Form
#3

Sometimes you have to compromise on the phosphor shape a bit in order to avoid moire patterns with the scanlines. A mask height of 3 does not play nicely with odd-numbered integer scales, introducing moire patterns with the scanlines (inconsistent scanline width/shape). E.g., for a mask height of 3, you should use an integer scale of 2, 4, 6, 8, etc. (apparently there is an option in Megatron to compensate for this - thanks @Cyber)

Do you mean height 2? Anyway, it was worth to take a look at the presets to get some ideas for tweaking for my lower res/lower brightness displays :+1: One thing I would personally change if you tweak it further is differentiating sharpness more according to mask TVL.

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#4

It’s a bit confusing - “mask height 2” corresponds to a triad that is 3 pixels tall (horizontal black line every 4th pixel)

You’re right- the sharpness settings should be tailored to the TVL. This is something I started working on, but I gave up. I couldn’t really find anything to improve RGB sharpness, but I think there’s some room for improvement with NTSC sharpness. I’ll see what I can do!

#5

I don’t understand why horizontal and substractive sharpness have to be fixed to 6.0/2.0 then. Are there major effects if you would lower it to something like 5.0/1.0?

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#6

6.00/2.00 is the sharpest I could get without introducing detectable artifacts, but if one wants to lower sharpness as a matter of taste, I don’t think there’s a problem with it.

Compared to 5.00/1.00, 6.0/2.0 is a bit sharper with fine details, but we’re talking like single-phosphor differences in sharpness, now. You can check the menu screen on 240p Test Suite for this. I also used the black line around the green pipe in Super Mario Bros :stuck_out_tongue: You can crawl forward with Mario (just tap forward) and slowly scroll while observing the black line. This is mostly a thing with RRGGBBX. If you go too high with sharpness, text on Test Suite menu screen gets all rainbowy. If you go too high you can also see how things almost become less sharp when looking at some high contrast edges, in some situations- it’s kind of a color bleed effect. Going higher with sharpness caused some additional problems that can be seen in the Scroll Test - Try 15.00/2.00 with RRGGBBX and you can see what I mean.

I think 6.00/2.00 is pretty close to optimized for RRGGBBX but I’m still looking for ways to improve it, if possible. Let me know if you find something! I need to take a closer look at each TVL and see if anything can be done- I didn’t notice anything obviously wrong with 6.00/2.00 at other TVLs but there could still be room for improvement.

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#7

I think this should count:

Peak 10% Window 1,466 cd/m²

Peak 25% Window 1,378 cd/m²

Sustained 10% Window 1,443 cd/m²

Sustained 25% Window 1,364 cd/m²

I took all of them for a spin. Brightness and saturation wise, they looked great even using my HDR settings in RetroArch but only for NES and possibly N64 though. My first encounter was with Legendary Axe II on the Turbografx16/Duo and it was a bit washed out and over sharpened for my taste.

With Super Mario Bros. on the NES things looked much better. My biggest issue was with the vertical lines that are supposed to be black, for example in the pipes, I found the contrast to be a bit low and the high levels of fringing and artifacting only exacerbated that. Turning both parameters down resulted in a much more palatable experience for me. Leaving them as is only compounded the lack of BFI and relatively poor motion by my VA panel.

I had to switch to Mask Layout 1 to match my display’s subpixel output but that resulted in probably worse colours than Layout 0 for the MG masks. Perhaps those only work correctly on R-G-B layout displays?

Judging from these presets, we seem to have similar tastes in what constitutes a good CRT shader preset.

I know you’ve been baptised in CRT-Guest-Advanced but don’t hesitate to give my most recent shader stacks a whirl which combine elements of Sony Megatron Colour Video Monitor, CRT-Guest-NTSC, Grade, ImgMod and there are some with and without XBR.

The two most recent and possibly best stacks are my current “Epic” 18 pass shader stack and my “W2” and “Sharp Neo-GX” 12 pass shader stack which deliberately omitted any smoothing shaders in favour of getting the smooth/sharp recipe fine tuned by mainly just using NTSC settings.

If you don’t like any smoothing, it can even be sort of bypassed or minimized even while using the “Epic” 18 pass stack.

These can be found in my miniLED and miniLED Epic preset packs.

One key trick I’ve learned recently is to cleanup any “noise” in the scanlines caused by little pieces of rendered vertical slot mask that might be better off culled by reducing the Scanline Max. While the Scanline Min can be used to fine tune the darker/narrow end of the scanline dynamics.

I recently updated my Old Skool Arcade Epic preset to reflect this.

The Shader Parameter in question is called “Vertical Center”.

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#8

Found a complete list of HDR1400 products here:

https://displayhdr.org/certified-products/

Probably not in my budget any time soon!

I think you’re referring to NTSC preset sharpness? I think I found some improvements to the horizontal filter, I’ll post soon. The Artifacting/Fringing is a matter of taste IMO and should be adjusted as desired.

Yes, I probably should have mentioned that- that could be affecting sharpness and color, definitely.

I admit I haven’t tested with TG16- that had a unique composite output (much like Genesis) and probably needs a fine-tuning. This is probably a decent starting point, though.

That’s a neat trick- I often use the beam min/max to fine tune, very handy. I’ll check this out.

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#9

I think I found some improvements to the horizontal filter, this is basically as sharp as RGB but still blends dithering:

ntsc_sharp = "-4.000000"
HSHARPNESS = "1.800000"
SIGMA_HOR = "0.400000"
S_SHARP = "1.600001"
HSHARP = "2.000000"
MAXS = "0.200000"
HARNG = "0.600000"
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#10

I updated to 1.21 (finally). Were there any changes to HDR? I swear I’m able to squeeze out a bit more brightness? Or possibly a change within guest-advanced (I updated shaders, too)?

I’m taking another look at some different combinations - I think low TVL + slot could be possible with the right HDR settings :thinking:

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#11

Great! Did you install the Nightly or Stable? It’s the Nightly that has the new Shaders Menu.

I don’t think there were any changes to HDR but CRT-Guest-Advanced has been undergoing changes at it’s usual rapid pace.

Depending on which version you were using before, you might have actually downgraded it or just installed a different version that’s not the latest.

I’ve stabilized my CRT-Guest-Advanced, Sony Megatron Colour Video Monitor and Mega Bezel Installations by installing them into different Folders.

I’ve recently revisited my Mega Bezel preset pack because I feel like the reflective bezel and background are the perfect solution to blooming/backlight bleed in the pillar boxes on an LCD when playing in a dark room and occasionally walking around.

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#12

Nope, lol. Let me try this again…

Yep, I’ve gotten into the habit of saving entire Retroarch versions and shaders :smiley:

Not a bad idea - the pillarboxes on an HDR1000 display with local dimming off look pretty terrible.

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#13

Remember, there’s also @Hyllian’s uBorder which supports CRT-Guest-Advance as well. uBorder is much lighter weight. I’m not sure when last CRT-Guest-Advanced has been updated for it though as CRT shaders need to be ported to ensure compatibility.

I’m sure @Hyllian won’t mind updating it if necessary.

It also supports Sony Megatron Colour Video Monitor and many other popular CRT shaders.

I even made one of the first uBorder CRT Shader preset packs during it’s early stages of development:

Spoiler

The latest RetroArch Nightly finally allows us to overwrite and update the currently active preset without remembering and retyping it’s filename. It also displays the currently active preset and allows us to revert any unsaved changes made while tweaking with the push of a button!

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#16

Mask Review

Did a few more tests, came up with some rankings.

RRGGBBX: this is my favorite, it’s very bright and the lower TVL just has a great consumer feel, and it helps to disguise some stuff you don’t want to see when using composite video.

Dotmask: second favorite. It’s a bit darker, but capable of adequate brightness. The lower TVL looks really nice and the dotmask pattern has an interesting texture.

RGBX: third favorite. It’s bright, but the higher TVL isn’t as well suited for retro games IMO. It’s basically a PVM, if that’s your thing. Some games, particularly those designed with RGB in mind, can look really good with a higher TVL, but I usually just prefer a lower TVL. The mask is not really noticeable at all, even at close viewing distances, but you can still see it.

MGX: this one ranks a bit lower than the above, IMO, because although it’s a bit brighter the mask just isn’t very satisfying - it’s even higher TVL and you can’t really detect the mask at all at normal viewing distances. Just kinda darkens the image.

MGX-slot: same as above, but ranks lower because the mask stuff isn’t really noticeable and it’s darker.

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#17

Brightness Tests

Here are some measurements taken with a light meter, full white, 100% window, no scanline mode. Average of 3 readings, light meter placed against the screen. Round to the nearest whole number. Measurements in nits.

Mask			Nits

MGX:			412
RRGGBBX: 		350 
MGX+slot:		306
dotmask: 		300
RGBX:			300
RRGGBBX+slot:	263
RGBX+slot:		223

These readings agree nicely with my eyeballings of the masks in my previous post. I think the minimum for CRT-like brightness on a sample and hold display is around 300 before scanlines are applied. RRGGBBX+slot is just barely out of reach- the brightest I can get it is around 275 by fiddling with HDR settings. Maybe it’s enough in a dark room? This also means that RGBX+slot is also ruled out.

Scanlines actually consume a bit more brightness than I thought - here are the readings with my scanline profile applied:

Mask						Nits

MGX+scanlines:				314
RRGGBBX+scanlines:			264
MGX+slot+scanlines:			236
dotmask+scanlines: 			229
RGBX+scanlines:				225
RRGGBBX+slot+scanlines:		201
RGBX+slot+scanlines:		170

For reference, a high-end consumer CRT could achieve a maximum brightness of anywhere from 200-300 nits (full-screen white image). However, this was only briefly sustained and would drop slightly.

It’s important to also acknowledge that perceived brightness on a CRT was likely higher than a sample and hold display of the same nits, due to variable persistence of the electron beam. John Carmack did a talk at the 1st Oculus connect where he talked about the effect of persistence on perceived brightness.

It would be interesting to see if beam simulator on a high Hz display has an effect on perceived brightness, but my monitor only goes up to 160Hz.

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#18

It’s hard to pick a favourite but I feel the least connection to Trinitron Masks, but I do love the scanline dynamics they produce at higher TVLs.

I’ve also seen the brightest masks with the most vibrant colours with Trinitron Masks in Sony Megatron Colour Monitor.

When I used CRT-Guest-Advanced via Mega Bezel, my Shadow (Dot) Mask presets ended up the brightest with slot mask all else equal being the darkest.

I then attempted to normalize brightness among all 3 mask types in my Neo-GX preset pack.

Dot mask is starting to become my favourite for various practical as well as subjective reasons.

Firstly, the dynamics are almost as good as Trinitron. On our digital displays the roughness that the dot triads add to the scanline help make them look more "analogue’ to me.

It’s a bit like deconvergence, when it’s completely disabled, the phosphors and scanlines look a bit robotic.

I also tried using Fringing and Artifacts and found that they work well in many scenarios and also contribute to making the signal feel more analogue. I got used to fringing after a few minutues.

They don’t work when I’m trying to fake additional colours and transparency for Turbo Duo games though as they add err artifacts to the areas where there should be just new colours.

That’s the main reason for my 3D Comb Filter presets.

Slot Mask is probably challenging because of the extra darkness potential but it looks great once you get it right. I think I accomplished this with my Old Skool Arcade Epic Presets. I almost always use Slot Mask with Arcade games for authenticity but dot mask looks awesome here as well.

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#19

I know what you mean - low TVL slotmask is probably my ideal for most retro systems, but the brightness is just barely not there - HDR1400 should definitely get us the rest of the way there. It’s also possible that the perceived brightness of True Black HDR1000 will be higher than regular HDR1000.

It’s sort of “maybe adequate, takes a lot of work” vs “clearly works” for the ones I’ve recommended.

I haven’t made any attempt to do this since it would mean introducing clipping - I’m probably one or two clicks away from clipping something with my current configurations.

I’m also not using any brightness mitigations - even a single click on some things can yield a pretty significant gain in perceived/actual brightness- after you loosen that restriction, a lot more possibilities open up.

I like RRGGBBX and dotmask configuration about the same, I flip between the two depending on the mood. I think you’re right that the dotmask feels a bit more analogue, but RRGGBBX is quite a bit lower TVL, which has its own benefits - sometimes less is definitely more when it comes to pixel art.

I see you’ve been using a similar dotmask in some of your presets, looks good. As I recall reading, some of the earliest color TVs used a low TVL dotmask (Zenith Chromaclear)- this should probably be paired with a very smeary and blurry composite video signal for authenticity :stuck_out_tongue:

Yep, sometimes when you disable these completely it feels a little too perfect, and some things can look a bit better with a bit of fringing/artifacting. Artifacting 0.00 / Fringing 1.00 is probably as good as it gets for a CRT. Sometimes I like to crank things up a bit higher because it just feels right.

Yep, quite a bit - adding the slotmask is a ~25% loss of brightness according to my calculations and confirmed by tests.

I can get dotmask a lot brighter if I use a “standard” configuration- CRT Mask 4.00, Lottes MaskDark 0.00, MaskLight 1.00

This measures 296 nits using the same test settings as my above tests.

Since the RGB triad is 4 pixels wide at the widest point, that’s 540 TVL.

I’m using an alternative dotmask- Mask 10.00, (Transform to) Shadow Mask 1.00

This adds a black pixel, which prevents the red and blue phosphors from blurring together and helps with phosphor shape. Obviously, it’s a bit darker due to the addition of the black pixel.

The TVL is 432, so it’s a bit closer to consumer grade and has a bit more texture.

Taking another look at the Lottes configuration, it’s not that bad if you don’t mind sacrificing the phosphor shape a bit and don’t mind your reds and blues blurring into magenta. The extra brightness is definitely nice. It does need a bit of extra work to fine-tune, though, compared to the others- an HDR adjustment might be enough (needs a bit more contrast)

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#20

You can try RGB Mask 6 for dotmask then manipulate the size. That’s what I did for my Neo GX presets and when I was trying to match my CRT-Guest Advanced presets to My Megatron presets.

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#21

Looks to be the same as the Lottes layout above but without the weird color/brightness/etc shift.

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#22

Update:

-Replaced rgb presets with new presets using the ntsc version of the shader, tweaked for perfect sharpness/color/etc. The additional bit of processing looks better than the regular version of the shader- it’s actually capable of being a bit sharper with lower TVL masks.

-Spent quite a bit of time tweaking the horizontal filter- this should be the safe maximum for sharpness. Let me know what you think- best judged with a high TVL mask like MGX.

-Gamma corrected (standard 2.5/2.2) - helped color separation in highlights and improves the colors

-Adjusted beam profile accordingly. Try increasing Scanline Shape Bright Pixels and you’ll start clipping almost immediately. Try reducing it and the scanlines disappear over the brightest colors. Adjusted the dark beam as well to compensate for gamma adjustment.

-Added slight vertical deconvergence- I think it improves shade separation in highlights, lets you eek out a bit more brightness. Basically just gives you a bit more scanline variability. Plus, it looks good :slight_smile:

-To add slotmask, simply adjust “Slot Mask Strength Bright Pixels” and “Slot Mask Strength Dark Pixels” to 1.00. Only recommended if you have HDR1400…

-No more separate NTSC presets - instead, this handy cheat sheet can be used to adjust the parameters to whatever look you prefer :smiley:

Guest-Advanced-NTSC Shader Preset Cheat Sheet

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Please show off what crt shaders can do!
#23

Ok, quick update-

After some additional tests, gamma adjustment really should be done with the HDR settings when using HDR and left neutral in the shader (e.g., 2.4/2.4)

My original recommendations for HDR settings are mostly still good- Peak Luminance 1000, Paper White 750. Contrast should come down to ~5.00.

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