My TV (LG 79UF8609) does not support HDR over HDMI.
Using latest nightly 20190906. To play 4K-HDR/BT.2020 files with CE the ‘Tone map HDR to SDR’ option in CoreELEC-settings is used. After the option was changed always a reboot took place.
1 Option set to 'automatic’
1.1 Playing a 4K-HDR/BT.2020 movie:
Movie is too dark, compared with the same movie in the Bluray-version.
EOTF&Gamut are reported as SDR/BT.709
dispinfo during playing 4K-HDR/BT.2020: http://ix.io/1UJI
1.2 Now playing a full-HD/BT.709 movie (no reboot):
Colors are ok, EOTF&Gamut are shown as SDR/BT.709
dispinfo during playing full-HD/BT.709: http://ix.io/1UJJ
2 Option set to 'active’
same as set to ‘automatic’
3 Option set to 'off’
3.1 New CE-reboot with option set to ‘off’:
3.1.1 First movie played after reboot is a 4K-HDR/BT.2020 movie:
Colors are much brighter than with HDR2SDR-option set to ‘active’ or ‘automatic’, but
a little pale. Maybe this can be corrected by TV setup. But details are much much clearer,
picture impression is very good.
This has also be reported by NathanX (CoreElec Nightly - hdr 2 sdr does not work)
EOTF&Gamut are reported as SDR/BT.2020nc (that’s correct)
colour_primaries : BT.2020
transfer_characteristics : PQ
matrix_coefficients : BT.2020 non-constant
dispinfo during playing 4K-HDR/BT.2020: http://ix.io/1UHD
When the movie is stopped the colors of the CE-GUI are very oversaturated.
3.1.2 Second movie played (no reboot) is a full-HD/BT.709 movie:
Colors are MUCH too bright (reds are very oversaturated).
EOTF&Gamut are reported as SDR/BT.2020nc (as with the 4K-HDR/BT.2020 movie, that’ NOT correct).
But MediaInfo reported:
colour_primaries : BT.709
transfer_characteristics : BT.709
matrix_coefficients : BT.709
dispinfo during playing full-HD/BT.709: http://ix.io/1UJG
3.2 New CE-reboot with option set to ‘off’, now playing order is reversed (1st full-HD/BT.709, 2nd 4K-HDR/BT.2020):
3.2.1 first movie played after reboot now is the full-HD/BT.709 movie:
Colors are correct (as with option set ro ‘active’ or ‘automatic’.
EOTF&Gamut are reported as SDR/BT.709 (that’s correct)
dispinfo during playing full-HD/BT.709: http://ix.io/1UJF
After stopping the GUI-colors are correct.
3.2.2 second movie played is now the 4K-HDR/BT.2020 movie:
Picture is brighter as in case 1., but colors are washed out, faded and not brilliant.
EOTF&Gamut are reported as SDR/BT.709 (that’s NOT correct)
dispinfo during playing 4K-HDR/BT.2020: http://ix.io/1UJC
Setting the HDR2SDR-option to ‘Off’ plays BT.2020-files correctly (picture-impression is good).
But playing a BT.709-file next without reboot gives very oversaturated colors.
For me something goes wrong when switching the tonemapping between BT.709 and BT.2020 movies.