Add a NTSC NES color decoder shader, based on Bisqwit's code

misc/nes-color-decoder-alt.slang

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+#version 450
+
+/*
+   NES NTSC Color Decoder shader
+   Ported from Bisqwit's C++ NES Palette Generator
+   https://forums.nesdev.com/viewtopic.php?p=85060#p85060
+
+   Use with Nestopia or FCEUmm libretro cores with the palette set to 'raw'.
+*/
+
+layout(std140, set = 0, binding = 0) uniform UBO
+{
+   mat4 MVP;
+   vec4 OutputSize;
+   vec4 OriginalSize;
+   vec4 SourceSize;
+   uint FrameCount;
+} global;
+
+layout(push_constant) uniform Push
+{
+   float saturation;
+   float hue_tweak;
+   float contrast;
+   float brightness;
+   float gamma;
+} params;
+
+#pragma parameter saturation "Saturation" 1.0 0.0 5.0 0.05
+#pragma parameter hue_tweak "Hue" 0.0 -10.0 10.0 0.05
+#pragma parameter contrast "Contrast" 1.0 0.0 2.0 0.05
+#pragma parameter brightness "Brightness" 1.0 0.0 2.0 0.05
+#pragma parameter gamma "Gamma" 1.8 1.0 2.5 0.05
+
+#define saturation params.saturation
+#define hue_tweak params.hue_tweak
+#define contrast params.contrast
+#define brightness params.brightness
+#define gamma params.gamma
+
+bool wave (int p, int color)
+{
+   return ((color + p + 8) % 12 < 6);
+}
+
+float gammafix (float f)
+{
+   return f < 0.0 ? 0.0 : pow(f, 2.2 / gamma);
+}
+
+vec3 MakeRGBColor(int emphasis, int level, int color)
+{
+   float y = 0.0;
+   float i = 0.0;
+   float q = 0.0;
+
+   float r = 0.0;
+   float g = 0.0;
+   float b = 0.0;
+
+   // Voltage levels, relative to synch voltage
+   float black = 0.518;
+   float white = 1.962;
+   float attenuation = 0.746;
+   const float levels[8] = float[] (   0.350 , 0.518, 0.962, 1.550,
+                                       1.094, 1.506, 1.962, 1.962);
+   
+   float low  = levels[level + 4 * int(color == 0)];
+   float high = levels[level + 4 * int(color < 13)];
+   
+   // Calculate the luma and chroma by emulating the relevant circuits:
+   for(int p = 0; p < 12; p++) // 12 clock cycles per pixel.
+   {
+      // NES NTSC modulator (square wave between two voltage levels):
+      float spot = wave(p, color) ? high : low;
+
+      // De-emphasis bits attenuate a part of the signal:
+      if ((bool(emphasis & 1) && wave(p, 12)) ||
+          (bool(emphasis & 2) && wave(p, 4)) ||
+          (bool(emphasis & 4) && wave(p, 8))) 
+      {
+          spot *= attenuation;
+      }
+
+      // Normalize:
+      float v = (spot - black) / (white - black);
+
+      // Ideal TV NTSC demodulator:
+      // Apply contrast/brightness
+      v = (v - 0.5) * contrast + 0.5;
+      v *= (brightness / 12.0);
+
+      y += v;
+      i += v * cos((3.141592653 / 6.0) * (p + hue_tweak) );
+      q += v * sin((3.141592653 / 6.0) * (p + hue_tweak) );
+
+   }
+
+   i *= saturation;
+   q *= saturation;
+
+   // Convert YIQ into RGB according to a commonly used conversion matrix.
+   r = clamp((1.0 * gammafix(y +  0.956 * i +  0.621 * q)), 0, 1.0);
+   g = clamp((1.0 * gammafix(y + -0.272 * i + -0.647 * q)), 0, 1.0);
+   b = clamp((1.0 * gammafix(y + -1.105 * i +  1.702 * q)), 0, 1.0);
+
+   return vec3(r,g,b);
+}
+
+#pragma stage vertex
+layout(location = 0) in vec4 Position;
+layout(location = 1) in vec2 TexCoord;
+layout(location = 0) out vec2 vTexCoord;
+layout(location = 1) out float colorPhase;
+
+void main()
+{
+   gl_Position = global.MVP * Position;
+   vTexCoord   = TexCoord;
+}
+
+#pragma stage fragment
+layout(location = 0) in vec2 vTexCoord;
+layout(location = 1) in float colorPhase;
+layout(location = 0) out vec4 FragColor;
+layout(set = 0, binding = 2) uniform sampler2D Source;
+
+void main()
+{
+   vec4 c = texture(Source, vTexCoord.xy);
+
+   // Extract the chroma, level, and emphasis from the normalized RGB triplet
+   int color =    int(floor((c.r * 15.0) + 0.5));
+   int level =    int(floor((c.g *  3.0) + 0.5));
+   int emphasis = int(floor((c.b *  7.0) + 0.5));
+
+   vec3 out_color = MakeRGBColor(emphasis, level, color);
+   FragColor = vec4(out_color, 1.0);
+}

misc/nes-color-decoder-sony.slang

@@ -0,0 +1,139 @@
+#version 450
+
+/*
+   NES NTSC Color Decoder shader
+   Ported from Bisqwit's C++ NES Palette Generator
+   https://forums.nesdev.com/viewtopic.php?p=85060#p85060
+
+   Use with Nestopia or FCEUmm libretro cores with the palette set to 'raw'.
+*/
+
+layout(std140, set = 0, binding = 0) uniform UBO
+{
+   mat4 MVP;
+   vec4 OutputSize;
+   vec4 OriginalSize;
+   vec4 SourceSize;
+   uint FrameCount;
+} global;
+
+layout(push_constant) uniform Push
+{
+   float saturation;
+   float hue_tweak;
+   float contrast;
+   float brightness;
+   float gamma;
+} params;
+
+#pragma parameter saturation "Saturation" 1.0 0.0 5.0 0.05
+#pragma parameter hue_tweak "Hue" 0.0 -10.0 10.0 0.05
+#pragma parameter contrast "Contrast" 1.0 0.0 2.0 0.05
+#pragma parameter brightness "Brightness" 1.0 0.0 2.0 0.05
+#pragma parameter gamma "Gamma" 1.8 1.0 2.5 0.05
+
+#define saturation params.saturation
+#define hue_tweak params.hue_tweak
+#define contrast params.contrast
+#define brightness params.brightness
+#define gamma params.gamma
+
+bool wave (int p, int color)
+{
+   return ((color + p + 8) % 12 < 6);
+}
+
+float gammafix (float f)
+{
+   return f < 0.0 ? 0.0 : pow(f, 2.2 / gamma);
+}
+
+vec3 MakeRGBColor(int emphasis, int level, int color)
+{
+   float y = 0.0;
+   float i = 0.0;
+   float q = 0.0;
+
+   float r = 0.0;
+   float g = 0.0;
+   float b = 0.0;
+
+   // Voltage levels, relative to synch voltage
+   float black = 0.518;
+   float white = 1.962;
+   float attenuation = 0.746;
+   const float levels[8] = float[] (   0.350 , 0.518, 0.962, 1.550,
+                                       1.094, 1.506, 1.962, 1.962);
+   
+   float low  = levels[level + 4 * int(color == 0)];
+   float high = levels[level + 4 * int(color < 13)];
+   
+   // Calculate the luma and chroma by emulating the relevant circuits:
+   for(int p = 0; p < 12; p++) // 12 clock cycles per pixel.
+   {
+      // NES NTSC modulator (square wave between two voltage levels):
+      float spot = wave(p, color) ? high : low;
+
+      // De-emphasis bits attenuate a part of the signal:
+      if ((bool(emphasis & 1) && wave(p, 12)) ||
+          (bool(emphasis & 2) && wave(p, 4)) ||
+          (bool(emphasis & 4) && wave(p, 8))) 
+      {
+          spot *= attenuation;
+      }
+
+      // Normalize:
+      float v = (spot - black) / (white - black);
+
+      // Ideal TV NTSC demodulator:
+      // Apply contrast/brightness
+      v = (v - 0.5) * contrast + 0.5;
+      v *= (brightness / 12.0);
+
+      y += v;
+      i += v * cos((3.141592653 / 6.0) * (p + hue_tweak) );
+      q += v * sin((3.141592653 / 6.0) * (p + hue_tweak) );
+
+   }
+
+   i *= saturation;
+   q *= saturation;
+
+   // Convert YIQ into RGB according to the Sony CXA2025AS US decoder matrix.
+   r = clamp((1.0 * gammafix(y +  1.630 * i +  0.317 * q)), 0, 1.0);
+   g = clamp((1.0 * gammafix(y + -0.378 * i + -0.466 * q)), 0, 1.0);
+   b = clamp((1.0 * gammafix(y + -1.089 * i +  1.677 * q)), 0, 1.0);
+
+   return vec3(r,g,b);
+}
+
+#pragma stage vertex
+layout(location = 0) in vec4 Position;
+layout(location = 1) in vec2 TexCoord;
+layout(location = 0) out vec2 vTexCoord;
+layout(location = 1) out float colorPhase;
+
+void main()
+{
+   gl_Position = global.MVP * Position;
+   vTexCoord   = TexCoord;
+}
+
+#pragma stage fragment
+layout(location = 0) in vec2 vTexCoord;
+layout(location = 1) in float colorPhase;
+layout(location = 0) out vec4 FragColor;
+layout(set = 0, binding = 2) uniform sampler2D Source;
+
+void main()
+{
+   vec4 c = texture(Source, vTexCoord.xy);
+
+   // Extract the chroma, level, and emphasis from the normalized RGB triplet
+   int color =    int(floor((c.r * 15.0) + 0.5));
+   int level =    int(floor((c.g *  3.0) + 0.5));
+   int emphasis = int(floor((c.b *  7.0) + 0.5));
+
+   vec3 out_color = MakeRGBColor(emphasis, level, color);
+   FragColor = vec4(out_color, 1.0);
+}

misc/nes-color-decoder.slang

@@ -0,0 +1,139 @@
+#version 450
+
+/*
+   NES NTSC Color Decoder shader
+   Ported from Bisqwit's C++ NES Palette Generator
+   https://forums.nesdev.com/viewtopic.php?p=85060#p85060
+
+   Use with Nestopia or FCEUmm libretro cores with the palette set to 'raw'.
+*/
+
+layout(std140, set = 0, binding = 0) uniform UBO
+{
+   mat4 MVP;
+   vec4 OutputSize;
+   vec4 OriginalSize;
+   vec4 SourceSize;
+   uint FrameCount;
+} global;
+
+layout(push_constant) uniform Push
+{
+   float saturation;
+   float hue_tweak;
+   float contrast;
+   float brightness;
+   float gamma;
+} params;
+
+#pragma parameter saturation "Saturation" 1.0 0.0 5.0 0.05
+#pragma parameter hue_tweak "Hue" 0.0 -10.0 10.0 0.05
+#pragma parameter contrast "Contrast" 1.0 0.0 2.0 0.05
+#pragma parameter brightness "Brightness" 1.0 0.0 2.0 0.05
+#pragma parameter gamma "Gamma" 1.8 1.0 2.5 0.05
+
+#define saturation params.saturation
+#define hue_tweak params.hue_tweak
+#define contrast params.contrast
+#define brightness params.brightness
+#define gamma params.gamma
+
+bool wave (int p, int color)
+{
+   return ((color + p + 8) % 12 < 6);
+}
+
+float gammafix (float f)
+{
+   return f < 0.0 ? 0.0 : pow(f, 2.2 / gamma);
+}
+
+vec3 MakeRGBColor(int emphasis, int level, int color)
+{
+   float y = 0.0;
+   float i = 0.0;
+   float q = 0.0;
+
+   float r = 0.0;
+   float g = 0.0;
+   float b = 0.0;
+
+   // Voltage levels, relative to synch voltage
+   float black = 0.518;
+   float white = 1.962;
+   float attenuation = 0.746;
+   const float levels[8] = float[] (   0.350 , 0.518, 0.962, 1.550,
+                                       1.094, 1.506, 1.962, 1.962);
+   
+   float low  = levels[level + 4 * int(color == 0)];
+   float high = levels[level + 4 * int(color < 13)];
+   
+   // Calculate the luma and chroma by emulating the relevant circuits:
+   for(int p = 0; p < 12; p++) // 12 clock cycles per pixel.
+   {
+      // NES NTSC modulator (square wave between two voltage levels):
+      float spot = wave(p, color) ? high : low;
+
+      // De-emphasis bits attenuate a part of the signal:
+      if ((bool(emphasis & 1) && wave(p, 12)) ||
+          (bool(emphasis & 2) && wave(p, 4)) ||
+          (bool(emphasis & 4) && wave(p, 8))) 
+      {
+          spot *= attenuation;
+      }
+
+      // Normalize:
+      float v = (spot - black) / (white - black);
+
+      // Ideal TV NTSC demodulator:
+      // Apply contrast/brightness
+      v = (v - 0.5) * contrast + 0.5;
+      v *= (brightness / 12.0);
+
+      y += v;
+      i += v * cos((3.141592653 / 6.0) * (p + hue_tweak) );
+      q += v * sin((3.141592653 / 6.0) * (p + hue_tweak) );
+
+   }
+
+   i *= saturation;
+   q *= saturation;
+
+   // Convert YIQ into RGB according to FCC-sanctioned conversion matrix.
+   r = clamp((1.0 * gammafix(y +  0.946882 * i +  0.623557 * q)), 0, 1.0);
+   g = clamp((1.0 * gammafix(y + -0.274788 * i + -0.635691 * q)), 0, 1.0);
+   b = clamp((1.0 * gammafix(y + -1.108545 * i +  1.709007 * q)), 0, 1.0);
+
+   return vec3(r,g,b);
+}
+
+#pragma stage vertex
+layout(location = 0) in vec4 Position;
+layout(location = 1) in vec2 TexCoord;
+layout(location = 0) out vec2 vTexCoord;
+layout(location = 1) out float colorPhase;
+
+void main()
+{
+   gl_Position = global.MVP * Position;
+   vTexCoord   = TexCoord;
+}
+
+#pragma stage fragment
+layout(location = 0) in vec2 vTexCoord;
+layout(location = 1) in float colorPhase;
+layout(location = 0) out vec4 FragColor;
+layout(set = 0, binding = 2) uniform sampler2D Source;
+
+void main()
+{
+   vec4 c = texture(Source, vTexCoord.xy);
+
+   // Extract the chroma, level, and emphasis from the normalized RGB triplet
+   int color =    int(floor((c.r * 15.0) + 0.5));
+   int level =    int(floor((c.g *  3.0) + 0.5));
+   int emphasis = int(floor((c.b *  7.0) + 0.5));
+
+   vec3 out_color = MakeRGBColor(emphasis, level, color);
+   FragColor = vec4(out_color, 1.0);
+}

ntsc/ntsc-nes.slangp

@@ -0,0 +1,23 @@
+shaders = 3
+shader0 = ../misc/nes-color-decoder.slang
+shader1 = shaders/ntsc-pass1-composite-3phase.slang
+shader2 = shaders/ntsc-pass2-3phase.slang
+
+filter_linear0 = false
+filter_linear1 = false
+filter_linear2 = false
+
+scale_type0 = source
+scale0 = 1.0
+
+scale_type_x1 = absolute
+scale_type_y1 = source
+scale_x1 = 1024
+scale_y1 = 1.0
+frame_count_mod1 = 2
+float_framebuffer1 = true
+
+scale_type2 = source
+scale_x2 = 0.5
+scale_y2 = 1.0
+

presets/nes-color-decoder+pixellate.slangp

@@ -0,0 +1,7 @@
+shaders = "2"
+shader0 = ../misc/nes-color-decoder.slang
+shader1 = ../retro/shaders/pixellate.slang
+
+filter_linear0 = "false"
+scale_type0 = "source"
+scale0 = "1.000000"