HDR encoding

[mparade]

No, repeat headers won't help at all you need to enter all the her data. Can't tell you how to get all those infos from an existing stream though. Which is why Hybrid has no option for it.
-> unless you know all the data and set the appropriate flags the output might not get processed by your display the way you want.

Cu Selur

Mediainfo can read out of such sources the parameters as follows (theoretically, ):

Color range
Color primaries
Transfer characteristics
Matrix coefficients
Mastering display color primaries 
Mastering display luminance 
Maximum Content Light Level 
Maximum Frame-Average Light Level 

which can be set on the x265 command line manually. These infos can be determined during encoding surely.