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 HOOKED
//!BIND LUMA
//!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 HOOKED
//!BIND LOWRES_Y
//!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 sqr(x)      dot(x,x)
#define sigma_nsq   256.0/(255.0*255.0)

#define N           8

#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 = 1.0;

    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;
}

Doesn't look much different than spline36 from mpv (and without jpeg), just sharper.

Also these yellowish and blue strokes are part of the original image

Chroma bleeding sometimes happens with this shader, but FWIW it's mostly with a low bit-rate / quality images.

I didn't realize that those things are part of the original image LOL. Looks like KrigBilateral is trying to approach the original (also colors such as purple of the image above) and madvr's Bilateral sharp is trying to please human eyes IMO.

It seems krig cannot handle well when --video-rotate=90/270 is set in mpv.conf

Are you using hwdec? For me it happens only with hwdec and deband=no.

Yes, using"--hwdec=auto-copy". Except bilinear/oversample/bicubic_fast, there is no other cscale filters can perfectly show the rotated videos.

It's all mpv bugs.

Is it usable with HDR content? Or is it only for SDR?