slang-shaders/ntsc/shaders/ntsc-adaptive/ntsc-pass1.slang

#version 450

// NTSC-Adaptive
// based on Themaister's NTSC shader

layout(std140, set = 0, binding = 0) uniform UBO
{
   mat4 MVP;
   vec4 OutputSize;
   vec4 OriginalSize;
   vec4 SourceSize;
   uint FrameCount;
   float quality, bw;
} global;

#pragma parameter quality "Quality (Composite = 0, Svideo = 1)" 0.0 0.0 1.0 1.0
#pragma parameter bw "Black and White" 0.0 0.0 1.0 1.0

#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 vec2 pix_no;

void main()
{
   gl_Position = global.MVP * Position;
   vTexCoord = TexCoord;
   pix_no = TexCoord * global.SourceSize.xy * (global.OutputSize.xy / global.SourceSize.xy);
}

#pragma stage fragment
layout(location = 0) in vec2 vTexCoord;
layout(location = 1) in vec2 pix_no;
layout(location = 0) out vec4 FragColor;
layout(set = 0, binding = 2) uniform sampler2D Source;

#define PI 3.14159265
float phase = (global.OriginalSize.x > 300.0) ? 2.0 : 3.0;
float CHROMA_MOD_FREQ = (phase < 2.5) ? (4.0 * PI / 15.0) : (PI / 3.0);
float ARTIFACTING = 1.0 - global.quality;
float FRINGING = 1.0 - global.quality;
float SATURATION = 1.0 - global.bw;
// prevent some very slight clipping that happens at 1.0
const float BRIGHTNESS = 0.95;

mat3 mix_mat = mat3(
	BRIGHTNESS, FRINGING, FRINGING,
	ARTIFACTING, 2.0 * SATURATION, 0.0,
	ARTIFACTING, 0.0, 2.0 * SATURATION
);

const mat3 yiq2rgb_mat = mat3(
   1.0, 0.956, 0.6210,
   1.0, -0.2720, -0.6474,
   1.0, -1.1060, 1.7046);

vec3 yiq2rgb(vec3 yiq)
{
   return yiq * yiq2rgb_mat;
}

const mat3 yiq_mat = mat3(
      0.2989, 0.5870, 0.1140,
      0.5959, -0.2744, -0.3216,
      0.2115, -0.5229, 0.3114
);

vec3 rgb2yiq(vec3 col)
{
   return col * yiq_mat;
}

void main()
{
   vec3 col = texture(Source, vTexCoord).rgb;
   vec3 yiq = rgb2yiq(col);

   float chroma_phase = (phase < 2.5) ? PI * (mod(pix_no.y, 2.0) + mod(global.FrameCount, 2.)) : 0.6667 * PI * (mod(pix_no.y, 3.0) + mod(global.FrameCount, 2.));

   float mod_phase = chroma_phase + pix_no.x * CHROMA_MOD_FREQ;

   float i_mod = cos(mod_phase);
   float q_mod = sin(mod_phase);

   yiq.yz *= vec2(i_mod, q_mod); // Modulate.
   yiq *= mix_mat; // Cross-talk.
   yiq.yz *= vec2(i_mod, q_mod); // Demodulate.
   FragColor = vec4(yiq, 1.0);
}