New CRT shader from Guest + CRT Guest Advanced updates

RetroArch Additions Shaders
#5096

New Release Version (2025-10-27-r1):

Notable changes:

  • pal rf noise rework
  • rf noise also added to ntsc shaders
  • ntsc and pal versions: signal desaturation (safe voltages) feature removed (we all saw how this could work, at least)
  • additional option for pal chroma filtering, more authentic
  • edit: some technical improvements

Download link:

https://mega.nz/file/4swz0KjI#IgfCuYHLnIeYiSqNo0qgH3ph0tWgB6X4REvujXJW4nM

7 Likes
#5097

That’s unfortunate, I wish it stayed

1 Like
#5098

It was more or less for curiosity’s sake it was included in the first place. As i could read arround 0.85V is the upper limit, this would need chroma to be quite hot to trigger it.

Other reason is that emulators don’t have problems with this, and for same reasons blanking will also most probably not be considered with ntsc/pal shaders etc.

2 Likes
#5099

It was an interesting experiment but it didn’t have as much of an impact as I expected.

We can conclude that the main things influencing composite video color are the IQ conversion / compression / transmission, etc, and the TV’s decoder.

2 Likes
#5100

I think I got to the bottom of this. The color fringing is a problem that occurs with any mask that has this type of vertical stripe pattern: RRGGBB

Mask 6, CRT Mask Size 2 has the some color fringing problem as Mask 12.

Mask 13 is a similarly low TVL but doesn’t do the double phosphor thing, and doesn’t have the color fringing problem.

2 Likes
#5101

Hi @guest - Your PAL preset is really nice work! I hope that with the new Mega Bezel update, just as your NTSC variant is already present, the PAL variant will also be included. That said, starting from the basic shader settings, once I activate S-Video mode, in addition to reducing the various “noises” and artifacts, should I raise the PAL resolution scaling value to 2 or something else? And what about SCART mode? I’d like to make some changes that allow me to get as close as possible to these two types of signals, which are mainly the ones I used most at the time. Thanks for your help and for your tireless work.

1 Like
#5102

Hey @ROBMARK85, glad you like the pal shaders!

Maybe you can do small offset tweaks, it’s already approximating the s-video “resolution”, so only slight changes are viable.

It should be actually named RGB Scart mode, it has higher resolution set by default. You can do small tweaks with resolution scaling, also with “Internal Resolution” parameter, this goes for all modes.

Best with these connection type modes (RF, compisite, s-video, scart) is that you can also use them with any type of content with just small tweaks.

And if you want manual tuning only then use “PAL Resolution: Connection/Core” mode 2.0 and you can use Resolution Scaling + Internal resolution to fit your purpose.

These are basically all tricks for image sharpness.

#5103

So, and I apologize in advance for my ignorance, I just need to change the signal type (Composite, S-Video, etc.) and possibly adjust the “noise,” since the signal type selection already approximates the resolution. Is that correct? I hope I understand, thank you very much.

1 Like
#5104

You can also remove artifacting and fringing for s-video (it’s disabled by default for scart). Otherwise it’s quite reliable with “preset” mode, yes.

1 Like
#5105

Perfect, thank you so much!

1 Like
#5106

I did test them and seems they work fine, thanks! but I still miss “raster bloom” (breathing) in PAL :slightly_frowning_face:

1 Like
#5107

Alas, too bad shadow mask TVs weren’t mainstream in best times:

RoboCop (by $olo1870) EasyFlash-251027-185229
RoboCop (by $olo1870) EasyFlash-251027-1852291920×1440 1.88 MB

5 Likes
#5108

AzMods20251027, fully updated for crt-guest-advanced-2025-10-27-release1.

Readme with additional details

Built on top of:

  • Image Adjustment (2024.02.07) by hunterk

  • crt-guest-advanced-2025-10-27-release1 by guest.r and Dr. Venom, based in part on Themaister’s NTSC shader

  • Sony Megatron Colour Video Monitor (2023.10.09) by MajorPainTheCactus

  • with additional functions based on or inspired by Grade by Dogway

All included “CRT Megatron” presets are currently tuned for the LG C1 and other similar displays (WRGB subpixel layout, with approximately 800 nits Peak Luminance).

The included version of Image Adjustment has been modified to allow for finer control of the effects as i found appropriate.

crt-guest-advanced-ntsc has been modified to add or expand the following options

GPGX MS color fix

Corrects Genesis Plus GX’s Master System color output, which includes minor errors i discovered while implementing the Sega MS Nonlinear Blue Fix.

  • 0=off
  • 1=on (color saturation scaled to a maximum value of RGB 255)
  • 2=sat239 (scaled to a maximum value of RGB 239)
  • 3=sat210 (scaled to a maximum value of RGB 210)
  • 4=sat165 (scaled to a maximum value of RGB 165)

Sega MS Nonlinear Blue Fix

An implementation of the behavior described in Notes & Measures: Nonlinear Blue on Sega Master System 1 & Other Findings by bfbiii.

This setting automatically adjusts to work with the GPGX MS color fix settings.

Sega MD RGB Palette

An implementation/approximation of the Mega Drive/Genesis RGB palette as discussed here.

Downsample Pseudo Hi-Res

As i understand it, 15KHz CRT displays would treat double-horizontal resolution modes (512x224, 640x240, etc) as tho they were not doubled, resulting in a blending effect, called pseudo hi-res. A number of SFC/SNES games are known to have used this behavior for transparency effects, including Breath of Fire II, Jurassic Park, and Kirby’s Dream Land 3, and as far as i know it is the correct behavior for any device originally meant to be displayed on a 15KHz CRT TV/monitor.

  • 1 = off

  • 2 = Triggers the blending effect whenever the horizontal resolution is more than twice the vertical resolution. This works well with cores that either always output a pseudo hi-res image for compatibility (such as bsnes-jg), or cores that only use pseudo hi-res for pseudo hi-res content (such as SwanStation). True high-resolution/interlaced content is not effected.

  • 3 = Triggers the blending effect whenever the horizontal resolution is 480 or higher. This is needed for cores that display pseudo hi-res content in a true high-resolution container (such as Mesen-S and a number of bsnes variants). Unfortunately, this halves the resolution of true high-resolution/interlaced content, as there is no way to differentiate pseudo hi-res and true high-resolution/interlaced content in these cores.

Internal Resolution

Modified to allow up to 1/16th downsampling. (It’s a surprise tool that will help us later.)

Sony Megatron has been modified to add or expand the following options

HDR: Content Color Gamut

Out of the box, RetroArch and Megatron clamp colors to the Rec. 709 gamut (Expand Gamut set to Off in RetroAtch, or HDR: Original/Vivid set to Original in Megatron), or stretch that Rec. 709 gamut to an unusual non-standard gamut created by someone at Microsoft (?Chuck Walbourn?) called Expanded 709 (Expand Gamut set to On in RetroArch, or HDR: Original/Vivid set to Vivid in Megatron).

Obviously, this is undesirable, as all of the major “retro” color gamuts include colors that fall outside of Rec. 709.

Serendipitously, i found that it was possible to turn this problem into it’s own solution by simply adding additional color gamuts to the “HDR: Original/Vivid”, renaming it “HDR: Content Color Gamut” to better reflect it’s newfound purpose.

When using this setting, Colour System should be set to 0/r709, and Phosphors should be set to 0/NONE.

Options are as follows:

  • 0=Rec 709/sRGB (SDR HDTV/Windows gamut)
  • 1=Expanded 709
  • 2=NTSC 1953 (The OG color system that was only really used for like 5-8ish years back when basically no one owned a color TV anyway. If you are Brazillian or from a SECAM region, it may also match some old CRT TVs you’ve used with really weirdly intense greens? Hard to say. This sort of thing is kind of underdocumented.)
  • 3=RCA 1958 (?1961?) (Millennial’s grandparent’s old TV with weird colors #1.)
  • 4=RCA 1964 (Millennial’s grandparent’s old TV with weird colors #2.)
  • 5=SMPTE C/Rec 601-525 line/Conrac (Baseline standard gamut for Analog NTSC.)
  • 6=PAL/Rec 601-625 line (Baseline standard gamut for Analog PAL.)
  • 7=Dogway’s NTSC-J (Baseline standard gamut for Analog NTSC-J.)
  • 8=P22_80s (Dogway’s Grade gamut for 1980s-early 1990s TVs.)
  • 9=Apple RGB/Trinitron PC (Should approximate basically any Trinitron monitor from 1987-the mid to late 1990s. By the early 00s, they were SMPTE C instead, at least for high end monitors like the FW900.)
  • 10=guest’s Philips PC (Gamut used by a number of extremely popular monitors that used Philips tubes, including Philips CM8533, Philips VS-0080, and Commodore 1084)
  • 11=P22_90s (Dogway’s Grade gamut for mid 1990s TVs with tinted phosphors.)
  • 12=RPTV_95s (Dogway’s Grade gamut for late 90s/early 00s rear projection TVs that game manuals said you shouldn’t play games on due to burn in risk.)
  • 13=Display P3/P3-D65 (Common wide color gamut. Variant on the gamut used for film with shared primaries. Might be useful in the future if someone makes a WCG pixel game that looks best with a CRT shader?)
  • 14=Rec 2020 (HDR gamut. Again, might be useful in the future if someone makes a WCG pixel game that looks best with a CRT shader.)

Gamut Overshoot Fix

A fix MajorPainTheCactus came up with to deal with the color errors i noticed using lilium’s HDR analysis shader. (Sony Megatron Colour Video Monitor)

He decided not to implement it at the time, as he didn’t think it wouldn’t make a perceptible difference, but a friend and i both came to the conclusion that it makes certain test pattern colors look more like they do with no shaders applied, so i have continued to use it. There should be no downside. (Sony Megatron Colour Video Monitor)

  • 0=no fix
  • 1=the 7-decimal clamp
  • 2=the 6-decimal clamp (results in non-zero blacks, perceptible in a sufficiently dark room)

Scanline Multiplier/Divisor

Multiplies or divides the number of scanlines.

Useful for cases like DOS games meant for 31KHz displays, which output 320x200 that was then double scanned to 640x400.

The divisor options are handy for displaying increased internal resolution output from 3D cores that don’t include a good downsample option, such as PPSSPP. I strongly recommend using this setting in conjuction with crt-guest-advanced-ntsc’s Internal Resolution setting to reduce shimmering.

  • -1,0,1=1x (Default/off)
  • 2=2x (Doublescan)
  • 3=Auto 2x (Automatically doublescans any content with a vertical resolution of less than 300, while leaving higher resolution content unchanged)
  • -2=1/2 (Reduces the scanline count to one half default)
  • -3=1/3 (Reduces the scanline count to one third default)
  • -4=1/4 (Reduces the scanline count to one quarter default)
  • -5=1/5 (etc.)
  • -6=1/6
  • -7=1/7
  • -8=1/8
  • -9=1/9
  • -10=1/10
  • -11=1/11
  • -12=1/12
  • -13=1/13
  • -14=1/14
  • -15=1/15
  • -16=1/16
4 Likes
#5109

GO GUEST!!! These look wonderful.

1 Like
#5110

@guest.r seems adding it to PAL is not that hard

https://www.mediafire.com/file/1pj58e5zq5kzea3/raster+bloom+PAL.zip/file

need only 3 extra files (one of them just a stock)

1 Like
#5111

It’s not like adding it to pal preset chain, it’s more or less like adding raster bloom to the HD version. I want the HD version to be as it is for now, so please don’t be to zealous about it.

#5113

Has anyone found a good solution for the color fringing when using RRGGBB etc? Or is it just something we have to live with?

1 Like
#5114

I guess this is with ntsc shaders, can you explain the circumstances and settings? With 1440p my fauvorite aperture mask width is 4, which corresponds mask width 6 with 2160p. I can usually play normally with mask 10 etc.

Dunno, it might be the temporal effects, unless the display is doing something weird due to dimming zones.

1 Like
#5115

Cyber, brother hope all is well.

I’ve upgraded my setup since the last time we talked. Have been enjoying a lot of your presets. Will have to post pictures soon :call_me_hand:

2 Likes
#5116

It’s more noticeable with ntsc shaders but I still see it in standard guest-advanced using high sharpness settings.

You can see it with mask 12 on 240p Test Suite’s menu screen- the white text gets all rainbowy on the edges. Mask 6 size 2, same thing. Seems to occur with any configuration using doubled pixels for the mask. Maybe it’s just unavoidable with high sharpness. If I lower horizontal sharpness to about 5.00, the fringing goes away. So I may have just answered my own question :smiley:

2 Likes