Hdr10+

Discussion in 'CloneBD' started by Steve55, May 15, 2019.

  1. Steve55

    Steve55 Well-Known Member

    Please forgive my ignorance because I wasn’t sure where to post this question.
    I just saw in the release notes that HDR10+ is fully supported.
    I’m still very much on a learning curve for this stuff.
    Does this mean it will do all the tone mapping if I transcode? Could I define a device and transcode “for” that device?
    Just trying to understand at the moment.
     
  2. James

    James Redfox Development Team Staff Member

    It copies HDR10+, if present on the source disc.
    https://en.wikipedia.org/wiki/High-dynamic-range_video#HDR10+
     
    whatever_gong82 likes this.
  3. Steve55

    Steve55 Well-Known Member

    Hi James, "copying" I understand. But, if I am doing anything other than pass through, if I am transcoding, doesn't it need to know a theoretical target device? Especially, if I transcode to 8 bit? It needs to know how to apply the "hints" in the HDR10+ information.
    I'll shut up if this is the wrong place for asking.
     
  4. Pete

    Pete Forum Admin Staff Member

    If you're converting to 8 bits - the HDR10+ information is completely irrelevant, because the full colour dynamic of the scenes simply can't be carried over to that format.
    HDR10+ is - like DolbyVision - "backward compatible" to plain 10 bit HDR.

    What CloneBD does, is map colors and luminance values taken from the base HDR10 information down to the BT-709 color space with the help of splines (instead of just cutting it off at the edges, that would lose too much information).
    Any additional DV or HDR10+ information would simply get lost anyway.

    If you're merely compressing (maintaining HEVC10,) then CloneBD will retain the DV/HDR10+ information.
     
  5. Steve55

    Steve55 Well-Known Member

    Hi Pete
    Thanks so much for following up.
    I understood from elsewhere that the HDR+ would still be relevant for 8-bit, because you can't just "chop off" two bits and get the right "colour", the info in the HDR+ is still useful. Maybe I was misinformed there.
    But anyway, the rest of your reply I (think I) understood and gives me a picture of how CloneBD is working. So basically, it's ignoring the HDR+ to get to "standard" 10 bit and then doing some clever mapping.
    I have a lot to learn.
    Thanks again! Really appreciate.
     
  6. SamuriHL

    SamuriHL Retired Moderator

    The HDR10+ is dynamic metadata. Which means it describes a whole bunch of things about each frame of the movie. Dolby Vision uses a separate video track to carry that information. I've no real idea how HDR10+ is done but it appears embedded in the video track itself like HDR10. The point of HDR10+ is to provide additional metadata over the static metadata that HDR10 provides. Converting to 8 bit would probably defeat the purpose of the additional metadata but it still might help tonemapping alogorithms that can read the HDR10+ metadata. Maybe.
     
  7. James

    James Redfox Development Team Staff Member

    Maybe, but quite certainly not noticable.
     
  8. SamuriHL

    SamuriHL Retired Moderator

    My thought on this is that if one day madvr adds HDR10+ metadata support. It uses dithering to handle 8 bit so there's no real loss of data between 10 bit and 8 bit, but, the metadata could help with madvr's tonemapping (in theory, and that's still a maybe). Then again, madvr's tonemapping already surpasses HDR10+ in many way so maybe it's not relevant at all.