HDR10 rendering questions

I need to playback HDR10 content and draw some 2D over video. I think I understand how TV play HDR10|HLG|Dolby vision content, but I don’t understand how to do it from PC through video card with DirectX and OpenGL. I have Y’CbCr or R’G’B’ data in HDR10. My understanding:

  1. Switch display to HDR10 mode and send metadata - done
  2. Create framebuffer FP16 - done
    Then lot of questions:
  • framebuffer is in scRGB color format, right? Can be it changed to BT2020?
  • What is valid range of values? 0…1? -0.5…7.5? 0…14.5?
  • Does scRGB framebuffer contains linear values or gamma corrected?
  • How does video card translate/transform scRGB to output values? which is colorspace used for output to display? BT.2020? something else?
  • I need to convert BT.2020 colorspace to scRGB, correct?
  • Is there such conversion in open source?

PS. To simplify answers: I use Windows 10 and it is already switched to HDR mode.