Good test pattern: https://www.rtings.com/images/test-materials/2017/chroma-444.png (Compress it with any lossy codec first, for example jpeg. You can do it with mpv, only add screenshot-jpeg-source-chroma=no to mpv.conf). Usage: glsl-shader="~~/KrigBilateral.glsl"

KrigBilateral.glsl

// KrigBilateral by Shiandow
//
// This library is free software; you can redistribute it and/or
// modify it under the terms of the GNU Lesser General Public
// License as published by the Free Software Foundation; either
// version 3.0 of the License, or (at your option) any later version.
// 
// This library is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
// Lesser General Public License for more details.
// 
// You should have received a copy of the GNU Lesser General Public
// License along with this library.

//!HOOK CHROMA
//!BIND LUMA
//!BIND HOOKED
//!SAVE LOWRES_Y
//!WIDTH LUMA.w
//!WHEN CHROMA.w LUMA.w <
//!DESC KrigBilateral Downscaling Y pass 1

#define offset      vec2(0)

#define axis        1

#define Kernel(x)   dot(vec3(0.42659, -0.49656, 0.076849), cos(vec3(0, 1, 2) * acos(-1.) * (x + 1.)))

vec4 hook() {
    // Calculate bounds
    float low  = ceil((LUMA_pos - CHROMA_pt) * LUMA_size - offset - 0.5)[axis];
    float high = floor((LUMA_pos + CHROMA_pt) * LUMA_size - offset - 0.5)[axis];

    float W = 0.0;
    vec4 avg = vec4(0);
    vec2 pos = LUMA_pos;

    for (float k = low; k <= high; k++) {
        pos[axis] = LUMA_pt[axis] * (k - offset[axis] + 0.5);
        float rel = (pos[axis] - LUMA_pos[axis])*CHROMA_size[axis];
        float w = Kernel(rel);

        vec4 y = textureGrad(LUMA_raw, pos, vec2(0.0), vec2(0.0)).xxxx * LUMA_mul;
        y.y *= y.y;
        avg += w * y;
        W += w;
    }
    avg /= W;
    avg.y = abs(avg.y - avg.x * avg.x);
    return avg;
}

//!HOOK CHROMA
//!BIND LOWRES_Y
//!BIND HOOKED
//!SAVE LOWRES_Y
//!WHEN CHROMA.w LUMA.w <
//!DESC KrigBilateral Downscaling Y pass 2

#define offset      vec2(0)

#define axis        0

#define Kernel(x)   dot(vec3(0.42659, -0.49656, 0.076849), cos(vec3(0, 1, 2) * acos(-1.) * (x + 1.)))

vec4 hook() {
    // Calculate bounds
    float low  = ceil((LOWRES_Y_pos - CHROMA_pt) * LOWRES_Y_size - offset - 0.5)[axis];
    float high = floor((LOWRES_Y_pos + CHROMA_pt) * LOWRES_Y_size - offset - 0.5)[axis];

    float W = 0.0;
    vec4 avg = vec4(0);
    vec2 pos = LOWRES_Y_pos;

    for (float k = low; k <= high; k++) {
        pos[axis] = LOWRES_Y_pt[axis] * (k - offset[axis] + 0.5);
        float rel = (pos[axis] - LOWRES_Y_pos[axis])*CHROMA_size[axis];
        float w = Kernel(rel);

        vec4 y = textureGrad(LOWRES_Y_raw, pos, vec2(0.0), vec2(0.0)).xxxx * LOWRES_Y_mul;
        y.y *= y.y;
        avg += w * y;
        W += w;
    }
    avg /= W;
    avg.y = abs(avg.y - avg.x * avg.x) + LOWRES_Y_texOff(0).y;
    return avg;
}

//!HOOK CHROMA
//!BIND HOOKED
//!BIND LUMA
//!BIND LOWRES_Y
//!WIDTH LUMA.w
//!HEIGHT LUMA.h
//!WHEN CHROMA.w LUMA.w <
//!OFFSET ALIGN
//!DESC KrigBilateral Upscaling UV

#define sigma_nsq   256.0/(255.0*255.0)
#define N           8
#define sqr(x)      dot(x,x)

#define M(i,j)      Mx[min(i,j)*N + max(i,j) - (min(i,j)*(min(i,j)+1))/2]

#define C(i,j)      (inversesqrt(1.0 + (X[i].y + X[j].y) / Var) * exp(-0.5 * (sqr(X[i].x - X[j].x) / (localVar + X[i].y + X[j].y) + sqr((coords[i] - coords[j]) / radius))) /*+ (X[i].x - y) * (X[j].x - y) / Var*/)  // commented out part works well only on test patterns
#define c(i)        (inversesqrt(1.0 + X[i].y / Var) * exp(-0.5 * (sqr(X[i].x - y) / (localVar + X[i].y) + sqr((coords[i] - offset) / radius))))

#define getnsum(i)  X[i] = vec4(LOWRES_Y_tex(LOWRES_Y_pt*(pos+coords[i]+vec2(0.5))).xy, \
                                CHROMA_tex(CHROMA_pt*(pos+coords[i]+vec2(0.5))).xy); \
                    w = clamp(1.5 - abs(coords[i]), 0.0, 1.0); \
                    total += w.x*w.y*vec4(X[i].x, X[i].x * X[i].x, X[i].y, 1.0);

#define I3(f, n)    f(n) f(n+1) f(n+2)
#define I9(f, n)    I3(f, n) I3(f, n+3) I3(f, n+6)

vec4 hook() {
    vec2 pos = CHROMA_pos * HOOKED_size - vec2(0.5);
    vec2 offset = pos - round(pos);
    pos -= offset;

    vec2 coords[N+1];
    vec4 X[N+1];
    vec2 w;
    vec4 total = vec4(0);

    coords[0] = vec2(-1,-1); coords[1] = vec2(-1, 0); coords[2] = vec2(-1, 1);
    coords[3] = vec2( 0,-1); coords[4] = vec2( 0, 1); coords[5] = vec2( 1,-1);
    coords[6] = vec2( 1, 0); coords[7] = vec2( 1, 1); coords[8] = vec2( 0, 0);

    I9(getnsum, 0)

    total.xyz /= total.w;
    float localVar = abs(total.y - total.x * total.x) + sigma_nsq;
    float Var = localVar + total.z;
    float radius = 1.5;  // mix(1.5, 1.0, sigma_nsq / Var);

    float y = LUMA_texOff(0).x;
    float Mx[(N*(N+1))/2];
    float b[N];
    vec2 interp = X[N].zw;

    b[0] = c(0) - c(N) - C(0,N) + C(N,N); M(0, 0) = C(0,0) - C(0,N) - C(0,N) + C(N,N); M(0, 1) = C(0,1) - C(1,N) - C(0,N) + C(N,N); M(0, 2) = C(0,2) - C(2,N) - C(0,N) + C(N,N); M(0, 3) = C(0,3) - C(3,N) - C(0,N) + C(N,N); M(0, 4) = C(0,4) - C(4,N) - C(0,N) + C(N,N); M(0, 5) = C(0,5) - C(5,N) - C(0,N) + C(N,N); M(0, 6) = C(0,6) - C(6,N) - C(0,N) + C(N,N); M(0, 7) = C(0,7) - C(7,N) - C(0,N) + C(N,N);
    b[1] = c(1) - c(N) - C(1,N) + C(N,N); M(1, 1) = C(1,1) - C(1,N) - C(1,N) + C(N,N); M(1, 2) = C(1,2) - C(2,N) - C(1,N) + C(N,N); M(1, 3) = C(1,3) - C(3,N) - C(1,N) + C(N,N); M(1, 4) = C(1,4) - C(4,N) - C(1,N) + C(N,N); M(1, 5) = C(1,5) - C(5,N) - C(1,N) + C(N,N); M(1, 6) = C(1,6) - C(6,N) - C(1,N) + C(N,N); M(1, 7) = C(1,7) - C(7,N) - C(1,N) + C(N,N);
    b[2] = c(2) - c(N) - C(2,N) + C(N,N); M(2, 2) = C(2,2) - C(2,N) - C(2,N) + C(N,N); M(2, 3) = C(2,3) - C(3,N) - C(2,N) + C(N,N); M(2, 4) = C(2,4) - C(4,N) - C(2,N) + C(N,N); M(2, 5) = C(2,5) - C(5,N) - C(2,N) + C(N,N); M(2, 6) = C(2,6) - C(6,N) - C(2,N) + C(N,N); M(2, 7) = C(2,7) - C(7,N) - C(2,N) + C(N,N);
    b[3] = c(3) - c(N) - C(3,N) + C(N,N); M(3, 3) = C(3,3) - C(3,N) - C(3,N) + C(N,N); M(3, 4) = C(3,4) - C(4,N) - C(3,N) + C(N,N); M(3, 5) = C(3,5) - C(5,N) - C(3,N) + C(N,N); M(3, 6) = C(3,6) - C(6,N) - C(3,N) + C(N,N); M(3, 7) = C(3,7) - C(7,N) - C(3,N) + C(N,N);
    b[4] = c(4) - c(N) - C(4,N) + C(N,N); M(4, 4) = C(4,4) - C(4,N) - C(4,N) + C(N,N); M(4, 5) = C(4,5) - C(5,N) - C(4,N) + C(N,N); M(4, 6) = C(4,6) - C(6,N) - C(4,N) + C(N,N); M(4, 7) = C(4,7) - C(7,N) - C(4,N) + C(N,N);
    b[5] = c(5) - c(N) - C(5,N) + C(N,N); M(5, 5) = C(5,5) - C(5,N) - C(5,N) + C(N,N); M(5, 6) = C(5,6) - C(6,N) - C(5,N) + C(N,N); M(5, 7) = C(5,7) - C(7,N) - C(5,N) + C(N,N);
    b[6] = c(6) - c(N) - C(6,N) + C(N,N); M(6, 6) = C(6,6) - C(6,N) - C(6,N) + C(N,N); M(6, 7) = C(6,7) - C(7,N) - C(6,N) + C(N,N);
    b[7] = c(7) - c(N) - C(7,N) + C(N,N); M(7, 7) = C(7,7) - C(7,N) - C(7,N) + C(N,N);

    b[1] -= b[0] * M(0, 1) / M(0, 0); M(1, 1) -= M(0, 1) * M(0, 1) / M(0, 0); M(1, 2) -= M(0, 2) * M(0, 1) / M(0, 0); M(1, 3) -= M(0, 3) * M(0, 1) / M(0, 0); M(1, 4) -= M(0, 4) * M(0, 1) / M(0, 0); M(1, 5) -= M(0, 5) * M(0, 1) / M(0, 0); M(1, 6) -= M(0, 6) * M(0, 1) / M(0, 0); M(1, 7) -= M(0, 7) * M(0, 1) / M(0, 0);
    b[2] -= b[0] * M(0, 2) / M(0, 0); M(2, 2) -= M(0, 2) * M(0, 2) / M(0, 0); M(2, 3) -= M(0, 3) * M(0, 2) / M(0, 0); M(2, 4) -= M(0, 4) * M(0, 2) / M(0, 0); M(2, 5) -= M(0, 5) * M(0, 2) / M(0, 0); M(2, 6) -= M(0, 6) * M(0, 2) / M(0, 0); M(2, 7) -= M(0, 7) * M(0, 2) / M(0, 0);
    b[3] -= b[0] * M(0, 3) / M(0, 0); M(3, 3) -= M(0, 3) * M(0, 3) / M(0, 0); M(3, 4) -= M(0, 4) * M(0, 3) / M(0, 0); M(3, 5) -= M(0, 5) * M(0, 3) / M(0, 0); M(3, 6) -= M(0, 6) * M(0, 3) / M(0, 0); M(3, 7) -= M(0, 7) * M(0, 3) / M(0, 0);
    b[4] -= b[0] * M(0, 4) / M(0, 0); M(4, 4) -= M(0, 4) * M(0, 4) / M(0, 0); M(4, 5) -= M(0, 5) * M(0, 4) / M(0, 0); M(4, 6) -= M(0, 6) * M(0, 4) / M(0, 0); M(4, 7) -= M(0, 7) * M(0, 4) / M(0, 0);
    b[5] -= b[0] * M(0, 5) / M(0, 0); M(5, 5) -= M(0, 5) * M(0, 5) / M(0, 0); M(5, 6) -= M(0, 6) * M(0, 5) / M(0, 0); M(5, 7) -= M(0, 7) * M(0, 5) / M(0, 0);
    b[6] -= b[0] * M(0, 6) / M(0, 0); M(6, 6) -= M(0, 6) * M(0, 6) / M(0, 0); M(6, 7) -= M(0, 7) * M(0, 6) / M(0, 0);
    b[7] -= b[0] * M(0, 7) / M(0, 0); M(7, 7) -= M(0, 7) * M(0, 7) / M(0, 0);

    b[2] -= b[1] * M(1, 2) / M(1, 1); M(2, 2) -= M(1, 2) * M(1, 2) / M(1, 1); M(2, 3) -= M(1, 3) * M(1, 2) / M(1, 1); M(2, 4) -= M(1, 4) * M(1, 2) / M(1, 1); M(2, 5) -= M(1, 5) * M(1, 2) / M(1, 1); M(2, 6) -= M(1, 6) * M(1, 2) / M(1, 1); M(2, 7) -= M(1, 7) * M(1, 2) / M(1, 1);
    b[3] -= b[1] * M(1, 3) / M(1, 1); M(3, 3) -= M(1, 3) * M(1, 3) / M(1, 1); M(3, 4) -= M(1, 4) * M(1, 3) / M(1, 1); M(3, 5) -= M(1, 5) * M(1, 3) / M(1, 1); M(3, 6) -= M(1, 6) * M(1, 3) / M(1, 1); M(3, 7) -= M(1, 7) * M(1, 3) / M(1, 1);
    b[4] -= b[1] * M(1, 4) / M(1, 1); M(4, 4) -= M(1, 4) * M(1, 4) / M(1, 1); M(4, 5) -= M(1, 5) * M(1, 4) / M(1, 1); M(4, 6) -= M(1, 6) * M(1, 4) / M(1, 1); M(4, 7) -= M(1, 7) * M(1, 4) / M(1, 1);
    b[5] -= b[1] * M(1, 5) / M(1, 1); M(5, 5) -= M(1, 5) * M(1, 5) / M(1, 1); M(5, 6) -= M(1, 6) * M(1, 5) / M(1, 1); M(5, 7) -= M(1, 7) * M(1, 5) / M(1, 1);
    b[6] -= b[1] * M(1, 6) / M(1, 1); M(6, 6) -= M(1, 6) * M(1, 6) / M(1, 1); M(6, 7) -= M(1, 7) * M(1, 6) / M(1, 1);
    b[7] -= b[1] * M(1, 7) / M(1, 1); M(7, 7) -= M(1, 7) * M(1, 7) / M(1, 1);

    b[3] -= b[2] * M(2, 3) / M(2, 2); M(3, 3) -= M(2, 3) * M(2, 3) / M(2, 2); M(3, 4) -= M(2, 4) * M(2, 3) / M(2, 2); M(3, 5) -= M(2, 5) * M(2, 3) / M(2, 2); M(3, 6) -= M(2, 6) * M(2, 3) / M(2, 2); M(3, 7) -= M(2, 7) * M(2, 3) / M(2, 2);
    b[4] -= b[2] * M(2, 4) / M(2, 2); M(4, 4) -= M(2, 4) * M(2, 4) / M(2, 2); M(4, 5) -= M(2, 5) * M(2, 4) / M(2, 2); M(4, 6) -= M(2, 6) * M(2, 4) / M(2, 2); M(4, 7) -= M(2, 7) * M(2, 4) / M(2, 2);
    b[5] -= b[2] * M(2, 5) / M(2, 2); M(5, 5) -= M(2, 5) * M(2, 5) / M(2, 2); M(5, 6) -= M(2, 6) * M(2, 5) / M(2, 2); M(5, 7) -= M(2, 7) * M(2, 5) / M(2, 2);
    b[6] -= b[2] * M(2, 6) / M(2, 2); M(6, 6) -= M(2, 6) * M(2, 6) / M(2, 2); M(6, 7) -= M(2, 7) * M(2, 6) / M(2, 2);
    b[7] -= b[2] * M(2, 7) / M(2, 2); M(7, 7) -= M(2, 7) * M(2, 7) / M(2, 2);

    b[4] -= b[3] * M(3, 4) / M(3, 3); M(4, 4) -= M(3, 4) * M(3, 4) / M(3, 3); M(4, 5) -= M(3, 5) * M(3, 4) / M(3, 3); M(4, 6) -= M(3, 6) * M(3, 4) / M(3, 3); M(4, 7) -= M(3, 7) * M(3, 4) / M(3, 3);
    b[5] -= b[3] * M(3, 5) / M(3, 3); M(5, 5) -= M(3, 5) * M(3, 5) / M(3, 3); M(5, 6) -= M(3, 6) * M(3, 5) / M(3, 3); M(5, 7) -= M(3, 7) * M(3, 5) / M(3, 3);
    b[6] -= b[3] * M(3, 6) / M(3, 3); M(6, 6) -= M(3, 6) * M(3, 6) / M(3, 3); M(6, 7) -= M(3, 7) * M(3, 6) / M(3, 3);
    b[7] -= b[3] * M(3, 7) / M(3, 3); M(7, 7) -= M(3, 7) * M(3, 7) / M(3, 3);

    b[5] -= b[4] * M(4, 5) / M(4, 4); M(5, 5) -= M(4, 5) * M(4, 5) / M(4, 4); M(5, 6) -= M(4, 6) * M(4, 5) / M(4, 4); M(5, 7) -= M(4, 7) * M(4, 5) / M(4, 4);
    b[6] -= b[4] * M(4, 6) / M(4, 4); M(6, 6) -= M(4, 6) * M(4, 6) / M(4, 4); M(6, 7) -= M(4, 7) * M(4, 6) / M(4, 4);
    b[7] -= b[4] * M(4, 7) / M(4, 4); M(7, 7) -= M(4, 7) * M(4, 7) / M(4, 4);

    b[6] -= b[5] * M(5, 6) / M(5, 5); M(6, 6) -= M(5, 6) * M(5, 6) / M(5, 5); M(6, 7) -= M(5, 7) * M(5, 6) / M(5, 5);
    b[7] -= b[5] * M(5, 7) / M(5, 5); M(7, 7) -= M(5, 7) * M(5, 7) / M(5, 5);

    b[7] -= b[6] * M(6, 7) / M(6, 6); M(7, 7) -= M(6, 7) * M(6, 7) / M(6, 6);

    b[7] /= M(7, 7);
    interp += b[7] * (X[7] - X[N]).zw;

    b[6] -= M(6, 7) * b[7]; b[6] /= M(6, 6);
    interp += b[6] * (X[6] - X[N]).zw;

    b[5] -= M(5, 6) * b[6]; b[5] -= M(5, 7) * b[7]; b[5] /= M(5, 5);
    interp += b[5] * (X[5] - X[N]).zw;

    b[4] -= M(4, 5) * b[5]; b[4] -= M(4, 6) * b[6]; b[4] -= M(4, 7) * b[7]; b[4] /= M(4, 4);
    interp += b[4] * (X[4] - X[N]).zw;

    b[3] -= M(3, 4) * b[4]; b[3] -= M(3, 5) * b[5]; b[3] -= M(3, 6) * b[6]; b[3] -= M(3, 7) * b[7]; b[3] /= M(3, 3);
    interp += b[3] * (X[3] - X[N]).zw;

    b[2] -= M(2, 3) * b[3]; b[2] -= M(2, 4) * b[4]; b[2] -= M(2, 5) * b[5]; b[2] -= M(2, 6) * b[6]; b[2] -= M(2, 7) * b[7]; b[2] /= M(2, 2);
    interp += b[2] * (X[2] - X[N]).zw;

    b[1] -= M(1, 2) * b[2]; b[1] -= M(1, 3) * b[3]; b[1] -= M(1, 4) * b[4]; b[1] -= M(1, 5) * b[5]; b[1] -= M(1, 6) * b[6]; b[1] -= M(1, 7) * b[7]; b[1] /= M(1, 1);
    interp += b[1] * (X[1] - X[N]).zw;

    b[0] -= M(0, 1) * b[1]; b[0] -= M(0, 2) * b[2]; b[0] -= M(0, 3) * b[3]; b[0] -= M(0, 4) * b[4]; b[0] -= M(0, 5) * b[5]; b[0] -= M(0, 6) * b[6]; b[0] -= M(0, 7) * b[7]; b[0] /= M(0, 0);
    interp += b[0] * (X[0] - X[N]).zw;

    return interp.xyxy;
}

It's all mpv bugs.

@igv: Could you change bind order, as in the diff below?

@@ -14,8 +14,8 @@
 // License along with this library.

 //!HOOK CHROMA
-//!BIND HOOKED
 //!BIND LUMA
+//!BIND HOOKED
 //!SAVE LOWRES_Y
 //!WIDTH LUMA.w
 //!WHEN CHROMA.w LUMA.w <
@@ -52,8 +52,8 @@ vec4 hook() {
 }

 //!HOOK CHROMA
-//!BIND HOOKED
 //!BIND LOWRES_Y
+//!BIND HOOKED
 //!SAVE LOWRES_Y
 //!WHEN CHROMA.w LUMA.w <
 //!DESC KrigBilateral Downscaling Y pass 2

What happens is that in fragment shader CHROMA_pos outputted from vertex shared is not used. And during the translation/optimization GLSL->SPIR-V->HLSL the actual input of the fragment shader is removed, which triggers validation error:

ID3D11DeviceContext::Draw: Vertex Shader - Pixel Shader linkage error: Signatures between stages are incompatible. Semantic 'TEXCOORD' of the input stage has a hardware register component mask that is not a subset of the output of the previous stage.

Basically we have this:
vertex:

struct SPIRV_Cross_Output
{
    float2 _9 : TEXCOORD0;
    float2 _13 : TEXCOORD1;
    float4 gl_Position : SV_Position;
};

fragment:

struct SPIRV_Cross_Input
{
    float2 _17 : TEXCOORD1;
};

and by changing the order, we use TEXCOORD0 and it is not tripping the validation. We can discard things from the end of input list, but not from beginning/middle.

Hope I make sense, just small workaround to make it work better when validation is enabled.