slang-shaders/crt/shaders/crt-maximus-royale/src/ntsc_rgbyuv.inc

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;
}