Koko-aio shader discussions and updates

kokoko3k · April 30, 2025, 10:06am

>> Starting from the code from 2024-June-13, Koko-aio needs at least Retroarch 1.16 to work <<

Version NG-1.9.70 is up on github and should be available via online updater in Retroarch.

Hi guys, first post here. In the past I made a shader for FS-UAE (Amiga emulation), but since i found that retroarch has a pretty good support for whdload games, I ported it to slangp so that it can be used with other emulators too.

I’m not that expert with technical terms, but i’m fortunate enough to own an old 15khz slot mask crt monitor inside an arcade cab loaded with Advance mame and other old emulators, so I used it as a reference. Why using a shader, you may ask, instead of the almost “real thing™”?

Actually that thing is big, heavy and power hungry and since it is running on an old AthlonXP i expect it to break sooner or later and i’ll not have spare time to fix, that’s for sure. Also, i’ve finally got an awesome oled 4k tv and i think that with that amazing (low) pixel persistance and resolution, we can get pretty damn close to the “real thing™”

One of the main goal of this shader is to be usable on integrated GPUs.
Granted, don’t expect it to run on a Raspberry pi, but the actual target is
Intel Haswell, the one on which I develop it, where it perform with all the features
enabled, when dealing with 240p content, on 1080p at resolution ad about 85/90fps.

Click to read features (outdated)

Scanlines
Screenlines
RGB phosphors
RGB deconvergence
NTSC/PAL CVBS color bleeding
Aperture grille, slot mask, shadomask.
Input signal glowing
Output signal glowing
Blooming
Gamma, contrast, saturation, luminance, color temperature adjustments
Black frame insertions through alternate blanking
Interlace flickering, forcing and emulation
Antialiasing
Curvature
Ambient lights
Vignette and Spotlight
Bezel (Thank you HyperspaceMadness for allowing me to rip his automagically generated bezel!) https://github.com/HyperspaceMadness/
Background images
Full screen glowing
3D rotation/tilt
Integer scaling
Background image Night mode
Support for backdrop images for BW game/CABs that use mirrors
NTSC emulation with selective artifacts smoothing
Temporal bloom
RF Noise
Dot matrix display emulation with grid, shadow and motion blur (gameboy mono)
Monochrome display “colorization”
TATE mode

Click to read relevant changes over previous releases

v1.9.70

New:

Phosphor triads with core resolution: Allow to target a TVL.
Backdrop: Permit to draw it just over the tube, Can now be used to simulate screen ambient reflections.
Allow to convert progressive input to interlaced.
make a generic low_fps() function that takes care of returning when content is under 30 or 35 fps.
Disable flickering on low fps interlaced content
interlacing + low level phophorgrid/scanlines: take halved period into account for fake integer scanlines activation
Add a function to clear “hives” like patterns when using dscanlines gap + slotmask

Changes:

Dot Crawl Tweaks
textures/boothill.jpg -> textures/backdrop.jpg

Fixes:

correctly scale slotmask dividers width to horizontal mask multiplier even when using core coords/size. BLAME ME FOR POSSIBLE REGRESSIONS
Correct warpedglow aspect
limit minimum warpedglow dynamic as i think there are rounding errors.
fix aliasing inside bezel border (evident when using high powered spot)
Slightly correct bezel aspect (4px wider texture)

Presets:

Add a preset that leverages TVL function
retweak GBA
do not use auto fake integer scanlines when using fake slotmask, since it mitigates moire already.
sharper Monitor-Screen_Hmask-Screen_SlotMask_Taller_Brighter
Monitor-Screen_Hmask-Screen_SlotMask_Taller_Brighter: trade hmask for scanlines, keep brightness
Improve Monitor-Screen_Hmask-Screen_SlotMask_Taller_Brighter.slangp
Monitor-Screen_Hmask-Screen_SlotMask_Taller/brighter, use dehive function, better slotmask
Tuned taller slotmas preset: switch grom BRG to GMX mask as it may give a more sparkling look (due to green being near black?)
presets: fine tune corners/edges

Performance:

Despite of new functions, performance is the same as the previous release.
Apply rgb mask multiplier in vertex shader, spare a vertex to fragment variable
BG_IMAGE_OVER: do not re-sample ambient light again
Do not sample ambient light again in fn_pixel_bezel()
skip a (now) useless ambient light re-sample
move border paint condition from canvas_bust to canvas_bezel_screen; *** blame me for regressions *** …That way it we can skip computing abientlight twice under the bezel.
warpedglow: 2 minor optimizations
Do not check if PIXELGRID_MIN_H < PIXELGRID_MAX_H, spare cycles. …please do not scanline max size < min_size in shader parameters
spare a div in fragment, done in vertex
Free 2 vec2 for 1 float in vertex shader, and spare a mul in fragment
flip coords due to tate: use mix_step instead of if/then (seems a bit faster)
Remove antimoire function, it is now a generic slotmask(fake) width override. …Set it to 1.0 and use Slotmask(fake) offset instead, to have the old behavior. …It should provides a performance boost over the previous method.

Useful links

Make sure to read the docs!
Main development done on this Github repo
Stable releases should be available through Retroarch’s online updater
(shaders_slang/bezel/koko-aio/) or here.
Click here if you want to try the latest in-develompent shader and unpack the zip somewhere inside your -already in place- shader directory.
I do not ensure you it will work as expected nor that your cat will be safe.
Texture “source” projects for main monitor frame/bezel and other misc files has been moved to another repo to lower the download size.
More presets and additional artworks: koko repo || estefan3112 repo || Starman99x repo || Duimon repo

If you want to boost your fps and you don’t mind tinkering with text files, take a look to the file config-user.txt in the shader folder and follow the instructions; on intel IGPs, I’ve seen fps boosted by 45%.

Please, tell me what you think, any comment is really appreciated.

Dynamic room lights (immersive preset)

Hires content

Overmasked

Antialiased

Mask experiments

Handhelds

Ntsc selective blurring and sharpening

monitor-Commodore_1084S-Night

monitor-slotmask-bloom-bezelwider - Arcade - Final fight

monitor-Commodore_1084S-wider - Amiga - ProjectX SE

tv-PAL-my-old - Master System - Trans Bot

tv-NTSC-1 - Genesis - Sonic 2

tv-NTSC-2 - Snes - Aladdin

tv-aperturegrille-bloom-bezel - Amiga - Leander

gameboy_mono_colorized.slangp - Gameboy mono - Super Mario Land

Hyllian · July 29, 2022, 1:29pm

Screenshots look great!

I tried testing it, but looks like you forgot to add curvature.slang to your repository. Retroarch gives that error.

kokoko3k · July 29, 2022, 1:59pm

Yep, sorry, and thanks! Just updated!

Hyllian · July 29, 2022, 2:30pm

Thanks! It worked now! I like your slotmask-bloom preset, using scanlines. Good for my tastes. I’m not very technical about crt shaders, so I just gave a completely subjective opinion.

Cyber · July 31, 2022, 12:06am

Looks really good! We’re now at a point where we’re spoiled with choices for great looking CRT Shaders!

You can take a look at what I’ve been able to come up with here as well as some other cool CRT Shader projects:

CyberLab Mega Bezel Death To Pixels Shader Preset Pack

Sony Megatron Color Video Monitor

The Guest-Advanced NTSC thread

The Guest-Advance, 100% mask strength thread

Example videos:

This is what CyberLab Turbo Duo for Blargg + Blargg_NTSC_Turbo_Duo_SNES_PSX_S-Video_CyberLab_Special_Edition looks like today!

CyberLab Turbo Duo for Blargg + Blargg_NTSC_Turbo_Duo_SNES_PSX_S-Video_CyberLab_Special_Edition

This is what CyberLab SNES looks like today!

CyberLab SNES

This is what CyberLab Genesis for Blargg + Blargg_NTSC_Genesis_S-Video_CyberLab_Special_Edition looks like today!

CyberLab Genesis for Blargg + Blargg_NTSC_Genesis_S-Video_CyberLab_Special_Edition

This is what CyberLab NES for Blargg + Core Blargg NTSC S-Video looks like today!

CyberLab NES for Blargg + Core Blargg NTSC S-Video

You can use MPC-HC, MX Player or VLC Player to view the videos.

Here’s a look at my latest preset!

CyberLab Ultimate Virtual Slot Mask CRT-1P2RTA

New Preset and System Recommendations

TVch34 Overlay

Plus

TVch34 Overlay + Mega Bezel

kokoko3k · July 31, 2022, 5:57am

Yeah, I’ve seen your presets, they are great. It seems to me they are targeting 4k resolutions, since you draw the triads horizontal gap too, right?

Do you have any comment or critic specific to work?

Cyber · July 31, 2022, 8:24am

Thanks!

My presets target 4K mainly but I’ve also tested and optimized presets for 1080p and to a lesser extent 1440p.

Most of them use RGB Mask including at 4K which uses the same mask with a size of 2 which would make it RRGGBB. This is mainly to remain compatible with displays that can’t do RGB Full 4:4:4 at 4K60Hz resolution, like one of my TVs.

Even after testing RRGGBBX masks initially, at 4K60Hz RGB Full 4:4:4, I still preferred RRGGBB because RRGGBBX TVL seemed lower.

However since I realized that in order to get “phosphor” triads to look properly on OLED TVs, I needed to use RRGGBBX mask with reversed Layout, I’ve started to include presets like that for use with OLED TVs.

I’m not one to be too critical, as I don’t even use a real CRT as a reference. I just tweak until stuff looks good to me and your work looks good!

I would just try to avoid making things even the slightest bit blurry especially when viewed from a distance because it’s tough on my eyes.

Keep up the great work!

kokoko3k · August 5, 2022, 12:50pm

With the new update you can now:

Emulate monitor curvature
Emulate a light spot (in the screenshot it is in the top/right corner)
Emulate a vignette effect (see in the screenshot that the monitor uniformity is uneven)
Emulate led ambient lights; by now the fade speed is slow and costant, but i plan to add a scene change detection euristic somehow to make the fades instant when the scene changes:

This is a WIP, you need to set aspect ratio to full in retroarch for the ambient light border to work. Also, the aspect ratio may be wrong in some configurations.

saeedalshaikhpygas · August 5, 2022, 1:26pm

Love what I’m looking at here , great stuff , I was wondering if it was possible to reduce the bloom radius less than 0.5 , Ideally to pixel perfect level ? the bloom can help restore some color but the “fog” bleeding can reduce the vibrance

The image below settings were adjusted to my display saturation ,it might look too saturated

kokoko3k · August 5, 2022, 1:36pm

For that maybe you can just disable blooming and use ‘halo’ setting?

kokoko3k · August 21, 2022, 3:07pm

In the latest commit i discovered the usefulness of mipmaps over retroarch downscaling

I may be wrong, but when scaling down using simpler scale#n=, even with bilinear filtering turned on, it seems to just discards whole lines.

Indeed I was in the need of a fast way to get the average luminance of the screen, and just scaling down to a 1x1 textures using absolute scale#n gave me just a pixel, probably from the middle of the texture.

Using mipmapping with a looow precision worked good instead and it gave me the perfect average luminance. This was handy to cheaply detect when a scene change.

That way, the “ambilight™” like effect is slow and not distracting when the scene is the same, but will instantly change when the scene changes.

The change is available in the latest commit.

hunterk · August 21, 2022, 6:41pm

Yes, you’re correct. Using the mips is the best way to get a fullscreen average.

kokoko3k · August 21, 2022, 8:05pm

Right then, so I need to rethink some other downscaling passes made for (big blurs) bloom and ambient lights itself. Thank you

edit: also, I wonder if downscaling this way is the correct behaviour of retroarch; since specifying bilinear filtering doesn’t change a thing; same very bad quality; It’s more like a decimation filter than a down scaler.

HyperspaceMadness · August 21, 2022, 7:49pm

If you set mipmap_input on for a pass it automatically takes a mipmapped version, so smoothed together if the resolution is lower.

I do this in a few passes in the Mega Bezel, an example is below, the first pass is really almost like the stock shader, but it linearize it so the blurs work properly and blend in linear space.

// Reduce Resolution  ----------------------------------------------------------------
//      Reduce the resolution to a small static size regardless of final resolution
//      Allows consistent look and faster at different final resolutions for blur
//      Mipmap option allows downscaling without artifacts
shader17 = ../../shaders/HyperspaceMadness/hsm/hsm-linearize-crt.slang
mipmap_input17 = true
filter_linear17 = true
scale_type17 = absolute
// scale_x17 = 480
// scale_y17 = 270
// scale_x17 = 960
// scale_y17 = 540
scale_x17 = 800
scale_y17 = 600
alias17 = "BR_MirrorLowResPass"

// Add Blur for the Reflection (Horizontal) ----------------------------------------------------------------
shader18 = ../../shaders/HyperspaceMadness/hsm/hsm-blur-outside-screen-horiz.slang
mipmap_input18 = true
filter_linear18 = true

// Add Blur for the Reflection (Vertical) ----------------------------------------------------------------
shader19 = ../../shaders/HyperspaceMadness/hsm/hsm-blur-outside-screen-vert.slang
filter_linear19 = true
alias19 = "BR_MirrorBlurredPass"

// Reduce resolution ----------------------------------------------------------------
// Reduced to a very small amount so we can create a blur which will create a glow from the screen
//      Mipmap option allows smoother downscaling
shader20 = ../../../../blurs/blur9x9.slang
mipmap_input20 = true
filter_linear20 = true
scale_type20 = absolute
scale_x20 = 128
scale_y20 = 128
alias20 = "BR_MirrorReflectionDiffusedPass"

// Add Diffused glow all around the screen ----------------------------------------------------------------
//      Blurred so much that it's non directional
//      Mipmap option allows downscaling without artifacts
shader21 = ../../../../blurs/blur9x9.slang
mipmap_input21 = true
filter_linear21 = true
scale_type21 = absolute
scale_x21 = 12
scale_y21 = 12
alias21 = "BR_MirrorFullscreenGlowPass"

kokoko3k · August 21, 2022, 8:06pm

So If i understood properly, this means i just need to set mipmap_input in the slangp preset and then normally use its scaling parameter and normal texture() lookup instead of textureLod() to get the mipmapped texture?

That would be handy!

HyperspaceMadness · August 21, 2022, 10:25pm

Yeah that’s what it seems to do, as if it was doing textureLod() and giving the correct mipmap level

kokoko3k · November 9, 2022, 1:14pm

Hi there, I just released 3.0 version.

The shader is faster (its gpu usage is under 65% with all of the features enabled on my poor Haswell igpu) and also looks better than ever to me.

The biggest addition is the bezel emulation for which I have to say a big thank you to HSM for allowing me to rip his automagically generated monitor frame to a simple png file.

However, the code implementation is very different from Mega Bezel, because koko-aio needs transparent areas for tube.
Adapting Mega Bezel backgrounds should still be possible with little work.
That said, standard/classic overlays works just fine, you just need to replace background.png and adapt zoom levels, curvature and image border right from the shader options. (see screenshot)

One thing still missing are presets for HiDPI screens.
If you like how the shader looks @1080p and have some free time, there are several options in the Mask area to hopefully make a preset that looks good with higher resolutions.

Yes, screenshot or it didn’t happen, ofc.

Fake, but cheap ntsc emulation:

Running with all bells and whistles and zoomed-in monitor frame

Zoomed out and with a background image reacting to ambient light,
cold color temperature

A standard Overlay, I just elarged “the hole”
with Gimp to allow the reflections to pass through too,
aperturegrille, shamelessly over-bloomed, because why not?

Some relevant changes from the latest releases:

Better denoise function
Allow to zoom out the output
Bezel and reflections
Interlace flickering emulation (you should see it live)
Several performance improvements (about 5% faster now)
Tweaked ambient light leds parameters
Better Bezel hilights and reflections
Whole image zooming depending on the content brightness
Improved scene detection logic for Ambient led lights
Bloom: allow to choose how much it affects bright colors
Allow to set an RGB Mask size for HiDPI screens
Allow to draw a gap between rgb mask triads
Presets tweaking
VMASK: implemented green-magenta to rgb subpixel layout
Add support for RGB offset
Add Contrast, brightness and color temperature controls
Add support for background or alpha driven foreground images
Add new “vibrant tv” and “fake ntsc” presets
Improved bloom look
Add simple chroma bleed option
Code cleanup

Comments always appreciated, critics needed, have fun!

SuperieurUltra · December 10, 2022, 7:45pm

Hi there.

I just saw the new version of the shader. I tested out the NTSC profile of the shader. Do you know how to get a more accurate NTSC effect so that dither patterns and vertical lines like those you see on Genesis games get blended better? Or do I have to mess around with the bandwidth limited chroma bleeding option? Nice shader by the way!

kokoko3k · December 11, 2022, 6:51am

Hi, full NTSC encoding/decoding is just not implemented (yet), so the specific “patterns to color” feature is something you cannot achieve. All of my systems was PAL, so I wasn’t interested in implementing it and by now the only thing you can do is to play with chroma bleeding, blur (input glow) and RGB shifting, but it will trick only untrained, naked eyes

SuperieurUltra · December 11, 2022, 11:03am

Ah ok, that’s a shame. I really like the “blurry composite” feel of the shader though.