OpenDX/src/d3d9/shaders/d3d9_convert_nv12.comp

#version 450
#extension GL_GOOGLE_include_directive : enable

#include "d3d9_convert_common.h"

layout(
  local_size_x = 8,
  local_size_y = 8,
  local_size_z = 1) in;

layout(binding = 0)
writeonly uniform image2D dst;

layout(binding = 1) uniform usamplerBuffer src;

layout(push_constant)
uniform u_info_t {
  uvec2 extent;
} u_info;

float fetchUnorm(usamplerBuffer source, uint offset) {
  return unpackUnorm(texelFetch(src, int(offset)).r);
}

void main() {
  ivec3 thread_id = ivec3(gl_GlobalInvocationID);

  if (all(lessThan(thread_id.xy, u_info.extent))) {
    uvec2 pitch = uvec2(u_info.extent.x, u_info.extent.y);

    // Format is:
    // YYYYYYYYYYYYYYY...
    // UVUVUVUVUVUVUVU...
    uint offset = thread_id.x
                + thread_id.y * pitch.x;

    float c0 = fetchUnorm(src, offset) - (16 / 255.0);

    // Floor .x to the nearest 2, because
    // UV data is in WORDs, and we want to get the color
    // for this pixel.
    // Then divide thread_id.y by 2 because the macropixel
    // layout for chroma data is [2, 2].
    offset = (thread_id.x / 2) * 2
           + thread_id.y / 2 * pitch.x
           + pitch.x * pitch.y;

    float u = fetchUnorm(src, offset)     - (128 / 255.0);
    float v = fetchUnorm(src, offset + 1) - (128 / 255.0);

    // The NV12 format seems to use the BT.703 color space.
    vec4 color0 = convertBT_703(vec3(c0, u, v));
    
    imageStore(dst, thread_id.xy, color0);
  }
}