BGRA.hpp

#pragma once
#include <Gfx/Graph/encoders/GPUVideoEncoder.hpp>
 
namespace score::gfx
{
 
struct BGRAEncoder : GPUVideoEncoder
{
  // Output byte order in memory (the RGBA8 texel bytes [0,1,2,3]).
  // NOTE: these are *memory* byte orders, which do NOT match AJA's NTV2_FBF_*
  // names — see the AJA FBF->memory mapping in AJAOutputNode (verified against
  // ntv2transcode.cpp ConvertARGBYCbCrTo*).
  enum class Swizzle
  {
    BGRA, // (b,g,r,a) — DXGI B8G8R8A8, QImage RGB32, NTV2_FBF_ARGB
    RGBA, // (r,g,b,a) — straight passthrough, NTV2_FBF_ABGR
    ABGR, // (a,b,g,r)
    ARGB  // (a,r,g,b) — NTV2_FBF_RGBA
  };
  Swizzle m_swizzle{Swizzle::BGRA};
 
  explicit BGRAEncoder(Swizzle s = Swizzle::BGRA)
      : m_swizzle{s}
  {
  }
 
  // %1 = the output swizzle expression.
  static constexpr const char* frag = R"_(#version 450
    layout(location = 0) in vec2 v_texcoord;
    layout(location = 0) out vec4 fragColor;
    layout(binding = 3) uniform sampler2D src_tex;
 
    vec2 flip_y(vec2 tc) {
    // Only OpenGL. The rest of the engine puts its geometry through
    // renderer.clipSpaceCorrMatrix, which negates Y on Vulkan; this pass draws
    // a hardcoded triangle in raw NDC and does not, so the correction it needs
    // is not the same one. Flipping on Vulkan as well handed libav, GStreamer,
    // NDI and every other consumer an upside-down picture.
    #if defined(QSHADER_SPIRV) || defined(QSHADER_MSL) || defined(QSHADER_HLSL)
      return tc;
    #else
      return vec2(tc.x, 1.0 - tc.y);
    #endif
    }
 
    void main() {
      vec4 c = texture(src_tex, flip_y(v_texcoord));
      fragColor = %1;
    }
  )_";
 
  QRhiTexture* m_outTexture{};
  QRhiTextureRenderTarget* m_renderTarget{};
  QRhiRenderPassDescriptor* m_rpDesc{};
  QRhiSampler* m_sampler{};
  QRhiShaderResourceBindings* m_srb{};
  QRhiGraphicsPipeline* m_pipeline{};
  QRhiReadbackResult m_readback{};
  int m_width{};
  int m_height{};
  bool m_readbackEnabled{true};
 
  void init(
      QRhi& rhi, const RenderState& state, QRhiTexture* inputRGBA, int width,
      int height, const QString& /*colorConversion*/ = colorMatrixOut()) override
  {
    m_width = width;
    m_height = height;
 
    m_outTexture = rhi.newTexture(
        QRhiTexture::RGBA8, QSize{width, height}, 1,
        QRhiTexture::RenderTarget | QRhiTexture::UsedAsTransferSource);
    m_outTexture->create();
 
    m_renderTarget = rhi.newTextureRenderTarget({m_outTexture});
    m_rpDesc = m_renderTarget->newCompatibleRenderPassDescriptor();
    m_renderTarget->setRenderPassDescriptor(m_rpDesc);
    m_renderTarget->create();
 
    m_sampler = rhi.newSampler(
        QRhiSampler::Linear, QRhiSampler::Linear, QRhiSampler::None,
        QRhiSampler::ClampToEdge, QRhiSampler::ClampToEdge);
    m_sampler->create();
 
    m_srb = rhi.newShaderResourceBindings();
    m_srb->setBindings({
        QRhiShaderResourceBinding::sampledTexture(
            3, QRhiShaderResourceBinding::FragmentStage, inputRGBA, m_sampler),
    });
    m_srb->create();
 
    const char* swiz = (m_swizzle == Swizzle::RGBA) ? "vec4(c.r, c.g, c.b, c.a)"
                       : (m_swizzle == Swizzle::ABGR)
                           ? "vec4(c.a, c.b, c.g, c.r)"
                       : (m_swizzle == Swizzle::ARGB)
                           ? "vec4(c.a, c.r, c.g, c.b)"
                           : "vec4(c.b, c.g, c.r, c.a)";
    auto [vertS, fragS] = makeShaders(
        state, QString::fromLatin1(vertex_shader),
        QString::fromLatin1(frag).arg(QString::fromLatin1(swiz)));
 
    m_pipeline = rhi.newGraphicsPipeline();
    m_pipeline->setShaderStages({
        {QRhiShaderStage::Vertex, vertS},
        {QRhiShaderStage::Fragment, fragS},
    });
    m_pipeline->setVertexInputLayout({});
    m_pipeline->setShaderResourceBindings(m_srb);
    m_pipeline->setRenderPassDescriptor(m_rpDesc);
    m_pipeline->create();
  }
 
  void exec(QRhi& rhi, QRhiCommandBuffer& cb) override
  {
    cb.beginPass(m_renderTarget, Qt::black, {0.0f, 0});
    cb.setGraphicsPipeline(m_pipeline);
    cb.setShaderResources(m_srb);
    cb.setViewport(QRhiViewport(0, 0, m_width, m_height));
    cb.draw(3);
 
    if(m_readbackEnabled)
    {
      auto* readbackBatch = rhi.nextResourceUpdateBatch();
      readbackBatch->readBackTexture(QRhiReadbackDescription{m_outTexture}, &m_readback);
      cb.endPass(readbackBatch);
    }
    else
    {
      cb.endPass();
    }
  }
 
  int planeCount() const override { return 1; }
 
  const QRhiReadbackResult& readback(int) const override { return m_readback; }
  QRhiTexture* outputTexture() const noexcept override { return m_outTexture; }
  void setReadbackEnabled(bool e) noexcept override { m_readbackEnabled = e; }
 
  void release() override
  {
    delete m_pipeline;
    m_pipeline = nullptr;
    delete m_srb;
    m_srb = nullptr;
    delete m_sampler;
    m_sampler = nullptr;
    delete m_rpDesc;
    m_rpDesc = nullptr;
    delete m_renderTarget;
    m_renderTarget = nullptr;
    delete m_outTexture;
    m_outTexture = nullptr;
  }
};
 
} // namespace score::gfx