UYVA.hpp

#pragma once
#include <Gfx/Graph/decoders/GPUVideoDecoder.hpp>
 
namespace score::gfx
{
 
struct UYVADecoder : GPUVideoDecoder
{
  static const constexpr auto frag = R"_(#version 450
 
)_" SCORE_GFX_VIDEO_UNIFORMS R"_(
 
layout(binding=3) uniform sampler2D y_tex;
layout(binding=4) uniform sampler2D a_tex;
 
layout(location = 0) in vec2 v_texcoord;
layout(location = 0) out vec4 fragColor;
 
%2
 
vec4 processTexture(vec4 tex) {
  vec4 processed = convert_to_rgb(tex);
  { %1 }
  return processed;
}
 
void main() {
   // UYVY packs U0 Y0 V0 Y1 into RGBA as x=U0 y=Y0 z=V0 w=Y1, so the texture
   // is half the width of the picture and each texel is two pixels.
   float colIndex = floor(v_texcoord.x * mat.texSz.x);
   float oddCol = mod(colIndex, 2.0);
 
   vec2 tc = score_tc(v_texcoord);
   vec2 dxInput = 0.5 * vec2(1.0 / mat.texSz.x, 0.0);
 
   float oddY = texture(y_tex, tc - dxInput).w;
   float evenY = texture(y_tex, tc + dxInput).y;
   float y = mix(evenY, oddY, oddCol);
   vec2 uv = texture(y_tex, tc).xz;
 
   // The alpha plane is full resolution, so it samples at the picture
   // coordinate rather than the half-width one.
   float a = texture(a_tex, tc).r;
 
   vec4 rgb = processTexture(vec4(y, uv.x, uv.y, 1.));
   fragColor = vec4(rgb.rgb, a);
}
)_";
 
  explicit UYVADecoder(Video::ImageFormat& d)
      : decoder{d}
  {
  }
 
  Video::ImageFormat& decoder;
 
  std::pair<QShader, QShader> init(RenderList& r) override
  {
    auto& rhi = *r.state.rhi;
    const auto w = decoder.width, h = decoder.height;
 
    auto mkSampler = [&] {
      auto sampler = rhi.newSampler(
          QRhiSampler::Linear, QRhiSampler::Linear, QRhiSampler::None,
          QRhiSampler::ClampToEdge, QRhiSampler::ClampToEdge);
      sampler->create();
      return sampler;
    };
 
    {  // UYVY, RGBA8 at half width
      auto tex = rhi.newTexture(QRhiTexture::RGBA8, {w / 2, h}, 1, QRhiTexture::Flag{});
      tex->create();
      samplers.push_back({mkSampler(), tex});
    }
    {  // alpha, one byte per pixel
      auto tex = rhi.newTexture(QRhiTexture::R8, {w, h}, 1, QRhiTexture::Flag{});
      tex->create();
      samplers.push_back({mkSampler(), tex});
    }
 
    return score::gfx::makeShaders(
        r.state, vertexShader(), QString(frag).arg("").arg(colorMatrix(decoder)));
  }
 
  void exec(RenderList&, QRhiResourceUpdateBatch& res, AVFrame& frame) override
  {
    {
      const auto [rows, offset] = planeRows(decoder, frame, decoder.height);
      auto sub = createTextureUpload(
          frame.data[0], decoder.width / 2, rows, 4, frame.linesize[0]);
      sub.setDestinationTopLeft({0, offset});
      res.uploadTexture(samplers[0].texture, QRhiTextureUploadDescription{{0, 0, sub}});
    }
    {
      const auto [rows, offset] = planeRows(decoder, frame, decoder.height);
      auto sub = createTextureUpload(
          frame.data[1], decoder.width, rows, 1, frame.linesize[1]);
      sub.setDestinationTopLeft({0, offset});
      res.uploadTexture(samplers[1].texture, QRhiTextureUploadDescription{{0, 0, sub}});
    }
  }
};
 
}