Hi,
a nice ffmpeg-suggestion to convert 10bit UHD HDR to SDR with HDR-like colours can be found at
https://stevens.li/guides/video/converting-hdr-to-sdr-with-ffmpeg/
I've worked out an example for the UHD disc Oblivion. In that example the 3840 * 2160 HEVC HDR source is converted to 1920 * 1080 x264 SDR:
ffmpeg -i oblivion.m2ts -map 0:v:0 -map 0:a:4 -map 0:a:0 -aspect 1920:816 -r 23.976 -vf crop=3840:1632:0:264,scale=1920:816,zscale=t=linear:npl=100,format=gbrpf32le,zscale=p=bt709,tonemap=tonemap=hable:desat=0,zscale=t=bt709:m=bt709:r=tv,format=yuv420p -c:v libx264 -preset fast -profile:v high -crf 18 -ac 2 -c:a aac -b:a 192k -metadata:s:a:0 language=ger -metadata:s:a:1 language=eng -y oblivion-1080p-sdr.mp4
What does this command do?
- it makes use of the video track (-map 0:v:0) and the german and english audio tracks (-map 0:a:4 -map 0:a:0)
- it crops the blackbars (crop=3840:1632:0:264)
- it scales the video down to 1080p (scale=1920:816 -> blackbars taken away, therefore 816 instead of 1080)
- the colour magic (HDR looking colours in an SDR video) is done by the string "zscale=t=linear:npl=100,format=gbrpf32le,zscale=p=bt709,tonemap=tonemap=hable:desat=0,zscale=t=bt709:m=bt709:r=tv,format=yuv420p" in the vf-option.
- the rest is standard: x264 with preset fast, nearly transparent quality by -crf 18, audio conversion and language -tagging
From my point of view it's harder to perform an x265 conversion keeping the HDR properties. Background: To do so, you cannot simply take the ffmpeg Zeranoe builds as they are 8 bit.
That's why you have to build your own ffmpeg 10 bit version which is much more challenging.