Overview: GPU subtitle overlay

GPU subtitle overlay uses supported interfaces to render or composite subtitle content with device-resident pictures.

OpenCL, CUDA and Vulkan paths have to agree with the picture representation entering and leaving the operation. Rendering the subtitle and compositing its image are also meaningful stages to identify. The pages below explain the GPU routes in that dataflow context, including the handoffs to other processing work.

• OpenCL subtitle overlay
  OpenCL subtitle composition operates on compatible device image planes, after subtitle content has been rendered into an accepted image representation.

• CUDA subtitle overlay
  CUDA subtitle composition blends accepted device video/image formats and remains distinct from text rendering, codec engines and the selected Emby graph.

• Vulkan subtitle overlay
  Vulkan overlay uses synchronized device images and a compute shader; subtitle rasterization, format matching and colour interpretation remain separate requirements.