Processing RAWs for HDR displays in Darktable

[age]

Simple steps to PQ encoding with darktable and ffmpeg (x265 output)

P1000657.RW2 (18.8 MB)
P1000657.RW2.xmp (20.7 KB)

1. load the image
   

   

2. add exposure compensation to taste
   

   

3. map 10000nits to 0-1 range (exposure setting -6.42)
   

   

4. export as rgb pq rec2020 tiff

5)encode with ffmpeg, in this step we only convert to ycbcr and attach the metadata

ffmpeg -loop 1 -t 10 -i P1000657.tif -vf scale=out_color_matrix=bt2020nc,format=yuv420p10 -c:v libx265 -preset medium -x265-params “colorprim=bt2020:transfer=smpte2084:colormatrix=bt2020nc:range=limited:master-display=G(13250,34500)B(7500,3000)R(34000,16000)WP(15635,16450)L(10000000,1):max-cll=1000,0.0001” out1.mp4

Simple steps to HLG encoding with darktable and ffmpeg
It can’t be done right now but the steps for hlg encoding are the follows
https://www.bbc.co.uk/rd/sites/50335ff370b5c262af000004/assets/592eea8006d63e5e5200f90d/BBC_HDRTV_PQ_HLG_Transcode_v2.pdf

1. load the raw and add exposure correction

2. map 1000 nits to range 0-1 ( pixels divided by 10 or exposure corretion tool -3.321 ev)

3. apply system gamma (γ=1.2+0.42Log10 (lw/1000)=1.2+0.42Log10 (1000/1000)=1.2)

4. eventually expand the 0-1 range to 0-12 range (based on what formula darktable use)

5. convert from “linear” to hlg