GLSL Shader problem,.. (is it a bug or am I doing something wrong?)

[Selur]

Using:

//!HOOK MAIN
//!BIND HOOKED
//!DESC Levels
// Define levels adjustment parameters
#define input_low 16.0
#define input_high 235.0
#define gamma 1.0
#define output_low 16.0
#define output_high 235.0
vec4 hook() {
   vec4 color = HOOKED_texOff(0);
   // Normalize input and output parameters to [0, 1] range
   float input_low_norm = input_low / 255.0;
   float input_high_norm = input_high / 255.0;
   float output_low_norm = output_low / 255.0;
   float output_high_norm = output_high / 255.0;
   // Apply input low/high levels
   vec3 normalized = (color.rgb - input_low_norm) / (input_high_norm - input_low_norm);
   
   // Ensure values are within the [0, 1] range before gamma correction
   normalized = clamp(normalized, 0.0, 1.0);
   // Apply gamma correction using 1/gamma
   vec3 gamma_corrected = pow(normalized, vec3(1.0 / gamma));
   // Apply output low/high levels
   vec3 adjusted_output = gamma_corrected * (output_high_norm - output_low_norm) + output_low_norm;
   // Ensure values are within the [0, 1] range
   color.rgb = clamp(adjusted_output, 0.0, 1.0);
   return color;
}

through:

# Imports
import vapoursynth as vs
# getting Vapoursynth core
import sys
import os
core = vs.core
# Import scripts folder
scriptPath = 'F:/Hybrid/64bit/vsscripts'
sys.path.insert(0, os.path.abspath(scriptPath))
# loading plugins
core.std.LoadPlugin(path="F:/Hybrid/64bit/vsfilters/Support/libvs_placebo.dll")
core.std.LoadPlugin(path="F:/Hybrid/64bit/vsfilters/SourceFilter/LSmashSource/LSMASHSource.dll")
# Import scripts
import validate
# Source: 'G:\TestClips&Co\files\test.avi'
# Current color space: YUV420P8, bit depth: 8, resolution: 640x352, frame rate: 25fps, scanorder: progressive, yuv luminance scale: limited, matrix: 470bg
# Loading G:\TestClips&Co\files\test.avi using LWLibavSource
clip = core.lsmas.LWLibavSource(source="G:/TestClips&Co/files/test.avi", format="YUV420P8", stream_index=0, cache=0, prefer_hw=0)
frame = clip.get_frame(0)
# Setting detected color matrix (470bg).
clip = core.std.SetFrameProps(clip=clip, _Matrix=5)
# setting color transfer (170), if it is not set.
if validate.transferIsInvalid(clip):
  clip = core.std.SetFrameProps(clip=clip, _Transfer=6)
# setting color primaries info (to 470), if it is not set.
if validate.primariesIsInvalid(clip):
  clip = core.std.SetFrameProps(clip=clip, _Primaries=5)
# setting color range to TV (limited) range.
clip = core.std.SetFrameProps(clip=clip, _ColorRange=1)
# making sure frame rate is set to 25fps
clip = core.std.AssumeFPS(clip=clip, fpsnum=25, fpsden=1)
# making sure the detected scan type is set (detected: progressive)
clip = core.std.SetFrameProps(clip=clip, _FieldBased=0) # progressive
# adjusting color space from YUV420P8 to YUV444P16 for vsGLSLLevels
clip = core.resize.Bicubic(clip=clip, format=vs.YUV444P16, range_s="limited")
with open("F:/Hybrid/64bit/vsfilters/GLSL/parameterized/Levels.glsl") as glslf:
  glsl = glslf.read()
clip = core.placebo.Shader(clip=clip, shader_s=glsl, width=clip.width, height=clip.height)
# adjusting output color from: YUV444P16 to YUV420P10 for NVEncModel
clip = core.resize.Bicubic(clip=clip, format=vs.YUV420P10, range_s="limited", dither_type="error_diffusion")
# set output frame rate to 25fps (progressive)
clip = core.std.AssumeFPS(clip=clip, fpsnum=25, fpsden=1)
# output
clip.set_output()

I expected the filtered and the unfiltered version to be identical, which they are not.

Is there a bug in vs-placebo? Am I using it wrong? Is there a bug in my shader code?

[quietvoid]

I don't know? You could always try using the shader in mpv.

[Asd-g]

//!HOOK MAIN means the shader is applied on RGB input and not on YUV (as supposed by the shader code).

[Selur]

So the shader needs to me rewritten to assume YUV input to work with placebo.Shader or is there a mistake in the shader that it doesn't work with RGB as intended?