How to add HDR10+ metadata generated by DaVinci Resolve Studio

[fabiov64]

I'm stuck in finding the right way to add the HDR10+ metadata generated by DaVinci Resolve to a video I edited. I'm following this workflow:

• setup a DaVinci Project with HDR10+ and output color space ST2084 1000 nits
• edit the project
• run the HDR10+ analysis
• export the HDR10+ metadata as json profile B
• deliver the project as ProRes 422HQ including HDR10 metadata (this step is needed because DaVinci h265 encoder sucks ....)
• encode the ProRes to mp4 using HandBrake
  Now the mediainfo shows a HDR10 compatible mp4 file
• extract the hevc stream: ffmpeg -i Test.mp4 -map 0:v:0 -c copy -bsf:v hevc_mp4toannexb -f hevc out_1.hevc
• inject the metadata from json file using hdr10tool: hdr10plus_tool inject -i out_1.hevc -j HDRJson.json -o injected.hevc
• mux the injected hevc file with the audio (extracted with ffmpeg), using MKVToolnix or mp4muxer
  With mediainfo, none of the obtained files (the mp4 and the mkv) shows HDR10+ capabilities.
  What am I doing wrong ?

[quietvoid]

I don't know, it should be working fine.
You could also check the MediaInfo before muxing.

[fabiov64]

The mediainfo on the injected hevc file does not tell anything about the HDR10+. But it's the same on injected Dolby Vision hevc files. Only after muxing them the DV infos are reported.

[quietvoid]

HDR10+ can be detected without muxing, so something is going wrong with your workflow.

[fabiov64]

I tried with a downloaded movie file, demuxing audio and video, extracting the json file and then removing the HDR10+ metadata. Running hdr10plus_tool I was able to re-add the metadata and after remixing everything is fine. As you wrote, mediainfo (with the -f option) is able to detect the HDR10+ metadata also in the hevc stream.
Now coming back to my workflow, it seems that when demuxing the mp4 file, the HDR10 info are removed. And this is probably the reason I cannot obtain a good HDR10+ file. Do you know a way to properly demux a HDR10 mp4 (or also mkv) preserving the HDR10 metadata ?

[quietvoid]

I don't know.
It sounds like your HEVC is not correctly encoded in the first place otherwise it would always say HDR10.

[fabiov64]

I don't know. It sounds like your HEVC is not correctly encoded in the first place otherwise it would always say HDR10.

I would exclude that. I tried to encode with Handbrake and Compressor. In both cases the mp4 is identified as SMPTE ST 2086, HDR10 compatible and it plays as a HDR file on my LGTV. But this is not maintained in the demuxed hevc.
When I add Dolby Vision metadata, everithing is working fine.

[fabiov64]

In the end I figured out what's going on: when encoding with Handbrake or Compressor and selecting the HW compression, the mp4 output seems to be good. But the de-muxed hevc stream is not. It means that probably the Mac HW VideoToolBox encoder writes the HDR10 metadata to the container only, not to the hevc stream. By opposite, selecting a SW compression method delivers the expected result: the hevc stream can be demuxed, keeping the HDR10 info and then it can be injected with HDR10+ metadata. And it works with both Compressor and Handbrake.
When working on Mac, the HW compression should be avoided if the final output needs to be de-muxed for some reason.