So this is probably nitpicking, but the above doesn’t hold for the first bar in the color bars test. See comparison below. The raw color value of this first bar is “12”, while the shader value will be stuck at “8” when the rest of the curve is fitted exactly or within ±10%.
I’m not sure if this should be fixed though, as it could well be that real CRTs power function could easily fall off more strongly as well when close to zero voltage output?
If you run the ‘new’ shader and the one from the libretro repository, there should be basically no notable changes, maybe a better glow in the new version.
I mentioned that ‘gamma correct’ is a tool to compensate the perceptive brightness reduction when thinning the scanlines, adding regular masks and the slotmask. With brightboost you get very different results regarding the color values and gamma combinations, but you practically cannot crank up the bright boost ‘bright’ since color clipping is something to be dealt with care.
Now there is 1 more tool (gamma correct) and it can be very helpful where brightboost has issues. You can also increase the monitor backlight intensity, but i guess most users aren’t comfortable with this.
Regarding the image…it’s tricky if you compare peak beam values and don’t take the ‘average area’ brightness into account. My personal preference will always be averaged brightness of the scanline with masks, but it’s tweakable and the default settings are quite neutral.
It’s really hard to compare though, since every CRT had it’s ways to tweak the brightness and even contrast. There are also differences between TN, IPS, VA, plasma and different models. Not to mention the tweaked gamma curve of the ‘new’ or ‘old’ technology plus the settings. I recently changed my display, my old one clipped scanlines (when i turned ‘magic color’ on) and had much lower contrast, for example. I just wan’t to say that it’s a lot of fun to discuss such matters, but very hard to consider the majority of the specific curious situations to be implemented in the shader.
The settings seem somewhat less intuitive now, but that might be because I’m used to doing extreme things to the shader. This definitely feels like starting completely from scratch, any advice for recreating my old guest-dr-venom preset (Type 0, the one that resembled a neotec arcade monitor)?
I think you will have better options with the new version(s). The most ‘drastic’ change is how scanlines type 1&2 correct the brightness (in a mitigated way), trinitron masks, scanline saturation (is not an issue at all). Gamma correction is an option, glow is tad slower, but nicer, brightboosts work as usual.
OK, i will change the ‘brightboost bright’ to replace Bloom and it has much more freedom now. 
Works the same when below 1.0 or slightly above 1.0, but can do some nicer stuff afterwards. I’m avoiding to make the code less reliable and feedback is very welcome, so it should work out nicely.
So you can tweak the old version a bit longer and check the ‘test versions’ a bit. I hope i’ll crack some nuts regarding some effects like afterglow etc. The main shader is nearly finished though, regressions are possible, but also fixable.
This sounds like a good idea; I dislike how the old bloom washes out the phosphors. Do you have a link to a test version?
Question about games / cores that run at double horizontal resolution. As we talked about previously this is happening for example sometimes in PSX core and always in PUAE core when resolution is set to Automatic. Lets forget about PSX core for now, as it -dynamically- switches between these resolutions (which is difficult to create solution for).
I only focus on PUAE core, as it can be set to a fixed / predictable situation. I’ll explain below.
Because of shader picture quality I previously set PUAE core option Resolution to “Low 360px”.
So now I noticed that interlace screens don’t work well when I set the core option for video resolution from Automatic to Low 360px. But I would like interlace screens to work well.
For interlace screens to work properly I need to set the following core options:
If you look closely the above conforms for the most situations to:
and only when interlace happens it switches the second to: Video > Line Mode: double
Everything fine for interlace. But because Resolution is now set to “Automatic” it effectively is at “High 720px” for everything and then shader output is too sharp for most games, as we discussed. But I need to have this at automatic for interlace to work properly.
So now my question: your shader is interpolating 5 or 6 pixels horizontally for effects? Could you tell me what I need to adjust in the shader code to have it interpolate the double amount of pixels (for example 10-12 pixels), such that it works the same when PUAE core is set to resolution Automatic (effectively High 720px)? Since it is always at 720px, never dynamically switching like PSX core, this should work?
I then would like to keep this version / patch seperately from the normal shader, so no need to worry to add extra code to main shader. I keep it purely as a patched shader for this core, all other cores use your normal shader. Or maybe, if it would be no burden to the shader, it’s even possible to do add a switch that internally in the shader, doubles the amount of pixels it takes for horizontal interpolation effect? That would be most charming solution! I would only switch it on for PUAE core and off for all other cores, and everything would be fine.
Please tell me it is possible to create this patch to accomodate for fixed double horizontal / 720px resolution 
It’s 6 texels, increased from 5 to get better filtering with high res content and even some increase in speed related with auxiliary stuff. It’s not going to change though, because i recently managed to get the shader performance similar to the old version. And the filtering is different, would make most users angry.
But you can try the NTSC version first (has 12 texel filtering) and i can adapt it for you (without the ntsc passes). This could work out even nicer since the NTSC version has a nice horizontal deconvergence implemented. Need some feedback first lol. 
Edit: almost forgot, you should replace the first two ntsc passes with the stock shader and set stock scalings to 1.0.
Edit: At the beginning of the crt-guest-dr-venom2-ntsc.slang main code part this line
vec4 SourceSize = global.OriginalSize * vec4(2.0, 1.0, 0.5, 1.0);
should be replaced with:
vec4 SourceSize = global.OriginalSize;
Thank you this works superb! I made a before and after screenshot comparison, and the difference is practically negligible. This is with same sharpness setting (5.20) for both situations, great!
Note: The “vec4 SourceSize” adjustment does not seem necessary, as it makes the picture at sharpness 5.20 a bit too blurry. EDIT: I think I need to test that a bit further by raising sharpness and see how it then compares.
Would it be possible to add this as a switch to your NTSC shader, or call it “RGB” mode (composite/s-video/rgb) that effectively disables the first two passes? Or does it need a separate preset?
Regardless of the above: could you maybe add the following two features from your main shader to the NTSC schader?:
I guess it can’t hurt, only make things better?
EDIT:
been playing around a bit more with the ntsc shader without the two ntsc passes for use with the PUAE core, and I think the default settings are looking pretty great, well done 
. I only changed the vertical glow radius by half, as I think the 2:1 pixel ratio also created this ratio for the glow, and with the V radius halved it looks nicely 1:1 hor/vert glow. Also interlaced screens look pretty great. All around very nice!
I’m not sure whether it would be possible, but of course the nicest thing would be if you could detect the source horizontal resolution and switch between the 6 and 12 texel interpolation accordingly (and maybe halve vert glow if in 12 texel mode), that could make it work for the dynamical resolution switching in the PSX core too?
EDIT2: did a test with the NTSC shader, replacing both NTSC passes with stock, but leaving the scaling factors for both of them as configured (4 and 0.5) and tried this on the SNES core. Just to compare with regular shader, and I have to say I like the “NTSC-stripped” quite a bit as an alternative to the regular shader. The “ntsc-stripped” one is capable of giving a softer image, without becoming blurry. Quite nifty 
.
Most likely needs a separate preset, afaik custom versions of the ntsc passes would have to be done for what you’re asking, mainly just a switch in the passes making them do nothing.
I think this is progress, still working on it though. Gray bars are still a bit weird. I like how the image stays nicely bright even with the increased mask strength, though. Still working without grade for now, since I broke it somehow and can’t figure out how to get it working again.
As always, scaling of the image has a pretty drastic effect on color/brightness/etc, only way to really judge settings is by firing up a game and seeing how it looks.
shaders = "10"
shader0 = "shaders_slang/crt/shaders/guest/lut/lut.slang"
filter_linear0 = "false"
wrap_mode0 = "clamp_to_border"
mipmap_input0 = "false"
alias0 = ""
float_framebuffer0 = "false"
srgb_framebuffer0 = "false"
scale_type_x0 = "source"
scale_x0 = "1.000000"
scale_type_y0 = "source"
scale_y0 = "1.000000"
shader1 = "shaders_slang/crt/shaders/guest/color-profiles.slang"
filter_linear1 = "true"
wrap_mode1 = "clamp_to_border"
mipmap_input1 = "false"
alias1 = ""
float_framebuffer1 = "false"
srgb_framebuffer1 = "false"
scale_type_x1 = "source"
scale_x1 = "1.000000"
scale_type_y1 = "source"
scale_y1 = "1.000000"
shader2 = "shaders_slang/crt/shaders/guest/d65-d50.slang"
filter_linear2 = "true"
wrap_mode2 = "clamp_to_border"
mipmap_input2 = "false"
alias2 = "WhitePointPass"
float_framebuffer2 = "false"
srgb_framebuffer2 = "false"
scale_type_x2 = "source"
scale_x2 = "1.000000"
scale_type_y2 = "source"
scale_y2 = "1.000000"
shader3 = "shaders_slang/crt/shaders/guest/afterglow.slang"
filter_linear3 = "true"
wrap_mode3 = "clamp_to_border"
mipmap_input3 = "false"
alias3 = "AfterglowPass"
float_framebuffer3 = "false"
srgb_framebuffer3 = "false"
scale_type_x3 = "source"
scale_x3 = "1.000000"
scale_type_y3 = "source"
scale_y3 = "1.000000"
shader4 = "shaders_slang/crt/shaders/guest/avg-lum.slang"
filter_linear4 = "true"
wrap_mode4 = "clamp_to_border"
mipmap_input4 = "true"
alias4 = "AvgLumPass"
float_framebuffer4 = "true"
srgb_framebuffer4 = "false"
scale_type_x4 = "source"
scale_x4 = "1.000000"
scale_type_y4 = "source"
scale_y4 = "1.000000"
shader5 = "shaders_slang/crt/shaders/guest/linearize.slang"
filter_linear5 = "true"
wrap_mode5 = "clamp_to_border"
mipmap_input5 = "false"
alias5 = "LinearizePass"
float_framebuffer5 = "true"
srgb_framebuffer5 = "false"
scale_type_x5 = "source"
scale_x5 = "1.000000"
scale_type_y5 = "source"
scale_y5 = "1.000000"
shader6 = "shaders_slang/crt/shaders/guest/linearize_scanlines.slang"
filter_linear6 = "true"
wrap_mode6 = "clamp_to_border"
mipmap_input6 = "false"
alias6 = "ScanPass"
float_framebuffer6 = "true"
srgb_framebuffer6 = "false"
scale_type_x6 = "source"
scale_x6 = "1.000000"
scale_type_y6 = "source"
scale_y6 = "1.000000"
shader7 = "shaders_slang/crt/shaders/guest/blur_horiz2.slang"
filter_linear7 = "true"
wrap_mode7 = "clamp_to_border"
mipmap_input7 = "false"
alias7 = ""
float_framebuffer7 = "true"
srgb_framebuffer7 = "false"
scale_type_x7 = "absolute"
scale_x7 = "800"
scale_type_y7 = "source"
scale_y7 = "1.000000"
shader8 = "shaders_slang/crt/shaders/guest/blur_vert2.slang"
filter_linear8 = "true"
wrap_mode8 = "clamp_to_border"
mipmap_input8 = "false"
alias8 = "GlowPass"
float_framebuffer8 = "true"
srgb_framebuffer8 = "false"
scale_type_x8 = "absolute"
scale_x8 = "800"
scale_type_y8 = "absolute"
scale_y8 = "600"
shader9 = "shaders_slang/crt/shaders/guest/crt-guest-dr-venom2.slang"
filter_linear9 = "true"
wrap_mode9 = "clamp_to_border"
mipmap_input9 = "false"
alias9 = ""
float_framebuffer9 = "false"
srgb_framebuffer9 = "false"
scale_type_x9 = "viewport"
scale_x9 = "1.000000"
scale_type_y9 = "viewport"
scale_y9 = "1.000000"
parameters = "TNTC;CP;CS;WP;wp_saturation;SW;AR;PR;AG;PG;AB;PB;sat;lsmooth;GAMMA_INPUT;SIZEH;GLOW_FALLOFF_H;SIZEV;GLOW_FALLOFF_V;glow;bloom;TATE;IOS;OS;BLOOM;brightboost;brightboost1;gsl;scanline1;scanline2;beam_min;beam_max;beam_size;decon;vertmask;scans;scansub;spike;h_sharp;s_sharp;csize;bsize;warpX;warpY;shadowMask;masksize;maskDark;maskLight;CGWG;mcut;slotmask;slotwidth;double_slot;slotms;inter;interm;gamma_out"
TNTC = "0.000000"
CP = "0.000000"
CS = "0.000000"
WP = "-50.000000"
wp_saturation = "1.000000"
SW = "1.000000"
AR = "0.070000"
PR = "0.050000"
AG = "0.070000"
PG = "0.050000"
AB = "0.070000"
PB = "0.050000"
sat = "0.100000"
lsmooth = "0.800000"
GAMMA_INPUT = "2.400000"
SIZEH = "4.000000"
GLOW_FALLOFF_H = "0.300000"
SIZEV = "4.000000"
GLOW_FALLOFF_V = "0.300000"
glow = "0.100000"
bloom = "0.000000"
TATE = "0.000000"
IOS = "0.000000"
OS = "1.000000"
BLOOM = "0.000000"
brightboost = "1.000000"
brightboost1 = "1.000000"
gsl = "2.000000"
scanline1 = "1.000000"
scanline2 = "20.000000"
beam_min = "2.000000"
beam_max = "1.000000"
beam_size = "0.000000"
decon = "0.000000"
vertmask = "0.000000"
scans = "0.500000"
scansub = "0.000000"
spike = "0.000000"
h_sharp = "3.000001"
s_sharp = "1.000000"
csize = "0.000000"
bsize = "600.000000"
warpX = "0.000000"
warpY = "0.000000"
shadowMask = "2.000000"
masksize = "1.000000"
maskDark = "0.500000"
maskLight = "1.000000"
CGWG = "0.300000"
mcut = "1.150000"
slotmask = "0.000000"
slotwidth = "2.000000"
double_slot = "1.000000"
slotms = "1.000000"
inter = "400.000000"
interm = "1.000000"
gamma_out = "2.200000"
textures = "SamplerLUT1;SamplerLUT2;SamplerLUT3"
SamplerLUT1 = "shaders_slang/crt/shaders/guest/lut/sony_trinitron1.png"
SamplerLUT1_linear = "true"
SamplerLUT1_wrap_mode = "clamp_to_border"
SamplerLUT1_mipmap = "false"
SamplerLUT2 = "shaders_slang/crt/shaders/guest/lut/sony_trinitron2.png"
SamplerLUT2_linear = "true"
SamplerLUT2_wrap_mode = "clamp_to_border"
SamplerLUT2_mipmap = "false"
SamplerLUT3 = "shaders_slang/crt/shaders/guest/lut/other1.png"
SamplerLUT3_linear = "true"
SamplerLUT3_wrap_mode = "clamp_to_border"
SamplerLUT3_mipmap = "false"
raise scanline shape low to 5.00:
I worked on the crt-guest-dr-venom shaders some more and i think they are complete or very close to completion (alas regressions) for now.
The changes are mostly nice or useful, nothing that would intentionally mess things up.
Notable changes (compared with previous version):
Download link:
https://mega.nz/file/5xwhwSRR#ipaipUOxYR36LFzpMnCtOZ9yW9uteT-N5Knlfcbc3As
Feedback is welcome. 
Quick question, what happened to the LUT pass in the presets?
My custom LUT doesn’t seem to work anymore, and I see you removed the LUT pass from the presets?
EDIT: ah I see you moved it to the “pre-shaders-…slang” pass. I just needed to set my lut size there 
Back to some testing
Hey, i knew you’d figure it out! 
Meanwhile i added 2 more ‘interlace’ modes 4&5 to the hi-res and ntsc versions. That was still on my mind to add. Also did some parameter range tweaking and cleanup.
Download link:
https://mega.nz/file/g0oXVAgb#7rwEzGqAbTBBxyxwfJ2-QwzVxUMmj8JOfVeJ37VjxWY
Edit: 4k support added for new interlaced modes (untested yet).
With Venom 2 it looks any passes you add to the top of the stack don’t work.
Might have to do with how it works now, what are you trying to put at the end of the chain?
Good catch! I was already on this, will add a stock as the first pass, which can be replaced and/or previous passes added.
Could you tell us the difference between the five types of interlace modes?
Mode0 disables ‘interlacing’.
Mode1 is the core mode, but only works with 50/60 fps content.
Mode2 is ‘baked’ mode 1 with no flickering, nice of 30fps content, screenshots or when convenient.
Mode3 is ‘vertical linear filtering mode’, if Mode2 is to blurry.
Mode4-Mode12 - best test it on preferably high res content.
Fixed now. It’s now possible to add custom prior passes or/and replace the first stock pass. ‘Interlace modes 6-12’ added (for different output resolutions convenience).
Download link
https://mega.nz/file/o9Qn1aBQ#Ir1pWTAAiAcddS8wmVsWXGBTm4Fa8vgMgWLRIiRRAmk
Edit: updated
Noticed a minor thing with the hires shader, the gamma out range is missing the 1.0 value in the range. This breaks gamma out as soon as you change the parameter in the shader.
#pragma parameter gamma_out "Gamma out" 1.8 5.0 0.05
#define gamma_out params.gamma_out // output gamma
Been playing a bit more with the ntsc shader and quite like it
Could you explain a bit the effect on what the scaling settings for the two passes below are actually achieving (first scaling x times 4.0 and then halving 0.5) in combination with the 12 pixel filtering? Just curious how you came about it as the effect is great; it gives a certain softness to the image without it becoming blurry
shader3 = shaders/guest/crt-gdv-new/ntsc/ntsc-pass1.slang
shader4 = shaders/guest/crt-gdv-new/ntsc/ntsc-pass2.slang
filter_linear3 = false
filter_linear4 = false
scale_type_x3 = source
scale_type_y3 = source
scale_x3 = 4.0
scale_y3 = 1.0
frame_count_mod3 = 2
float_framebuffer3 = true
scale_type4 = source
scale_x4 = 0.5
scale_y4 = 1.0
alias4 = NtscPass
With regards to gamma, I noticed you changed the default from 2.4/2.4 to 1.8/1.8, so I wondered why 1.8/1.8 is darker, whereas previously I assumed this gamma_input / gamma out was purely a gamma neutral operation “decoding/encoding” but apparently it’s not.
So my question below relates to gamma correction for “vintage game developer CRT gamma” versus my current LCD gamma . Supppose I have a gamma neutral output of the shader, but I would like to correct for the difference of the developers CRT monitor gamma, versus mine.
First case would not need adaption: Developer was on a pro monitor PVM (which is studio calibrated at gamma 2.2) versus mine sRGB LCD monitor which is also about 2.2.
But now suppose second case: Game developer developed end of the 80’s on a vintage CRT monitor, which has a gamma between 2.35 - 2.55 (depending on make/model)
So I would like to make an adjustment that would accurately describe the gamma correction of that developers CRT gamma versus my monitor. I.e. in extreme case I want to do a “2.2 / 2.55” correction or in least extreme case “2.2 / 2.35” gamma correction. So how do I do this in your shader?
I have four options:
Do you have an idea what is the most correct way to do an accurate gamma adjustment for the use case I put in bold above? I don’t want to end up with a correction which I think is theoretically correct, but in effect is actually breaking the gamma curve.
A very useful find indeed! Maintaining 3 versions sometimes lets some bugs slip. It should be caught by the shader compiler though. 
The ntsc passes don’t linearize input pixels by default, resulting in output, which looks like it should by these circumstances. I was holding to this look a bit with lowering the gamma. Its should be increased to 2.2 though since i thought about it a bit more.
Gamma is neutral, but there are more circumstances which involve color interpolation in the process. Glow has less influence with lower gamma, and the general look is affected by scanlines calculation - is interpolation with lower gamma, which produces a darker image. Also ‘color edges are darker’ etc.
You can’t break gamma cureve this simply in the shader. In a pass-through situation you get (color^(2.4))^(1.0/2.2) = color^1.091 etc. Interpolation makes things less predictable, so it’s more a matter of taste. You should use input gamma of your liking and tweak output gamma together with other variables. Without interpolation and shader parameter influence it would be much more simple though.
It’s IMO a way to let later passes to do some interpolation, since you typically still can do a 2-3x resizing afterwards. And later shaders have acceptable circumstances and don’t have to downsample themselves.
The 12 pixel interpolations with accommodated coefficients is a bit different, but it gives very nice results with the ntsc preset indeed. That’s why i gave myself some work, because former approach could be improved out of the box.
Anyway, shader is updated at above dl. link.