HLG HDR problem: very high contrast / saturation

I’m using a Vero 4k to play some MKVs that contain HLG HDR streams from the BBC. When I play them back with my CXUHD (an Oppo 203 clone), colors are rendered correctly, but it skips frames heavily. When playing back with the Vero, color saturation and contrast are extremely exaggerated. Neither triggers HDR mode in my projector (JVC DLA X5000). mplayer and VLC also display the videos correctly (only tested on a linux desktop with a “normal” SDR monitor).

Photos of the same scene:

mediainfo of one of the files:

Unique ID : 99347494048453647180414086559366152888 (0x4ABDA1A1625028BF1E76769E62F882B8)
Complete name : video.mkv
Format : Matroska
Format version : Version 4
File size : 7.55 GiB
Duration : 57 min 9 s
Overall bit rate : 18.9 Mb/s
Writing application : mkvmerge v68.0.0 (‘The Curtain’) 64-bit
Writing library : libebml v1.4.2 + libmatroska v1.6.4 / Lavf59.16.100

ID : 1
Format : HEVC
Format/Info : High Efficiency Video Coding
Format profile : Main 10@L5.1@Main
Duration : 57 min 2 s
Bit rate : 18.3 Mb/s
Width : 3 840 pixels
Height : 2 160 pixels
Display aspect ratio : 16:9
Frame rate mode : Constant
Frame rate : 25.000 FPS
Standard : Component
Color space : YUV
Chroma subsampling : 4:2:0
Bit depth : 10 bits
Bits/(Pixel*Frame) : 0.088
Stream size : 7.30 GiB (97%)
Default : Yes
Forced : No
Color range : Limited
Color primaries : BT.2020
Transfer characteristics : HLG
transfer_characteristics_Original : HLG / BT.2020 (10-bit)
Matrix coefficients : BT.2020 non-constant

My Vero 4k is up to date (it’s running the November 2022 release, if I’m not mistaken) Any suggestions what I can try to get my Vero to play back these files correctly? Any additional information I need to provide?

I’d suggest uploading some logs so we can see the EDID of your display and what we (OSMC) are trying to do re. output.

This will also let us check your settings to make sure they are optimal.

My Dune Real Vision acts strange with HLG/BBC files also (The English series) …I believe it has something to do with how the files are flagged.

Any chance of a short (say 1m) clip from an affected file?

Logs uploaded at https://paste.osmc.tv/ufitigihan

Samples at http://unimportant-site.com/stuff/darkff.mkv and http://unimportant-site.com/stuff/darkff2.mkv (a few seconds extracted with ffmpeg) and http://unimportant-site.com/stuff/dark.mkv (simply first 10MB of the file).

It’s difficult to judge whether the colours are ‘correct’ based on photos of a screen. To me the second pic looks a bit washed out. I’ve played your clips on two different TVs and they look fine to me - probably somewhere between the two photos you posted.

The EDID we are reading does not indicate support for HLG HDR so Vero is converting the signal to SDR. You could try setting HDR processing in Settings->Videos to BT2020SDR or Force SDR.

What do the Dune guys say about that, I wonder?

1 Like

I should clarify on my particular case…I use the Dunes Dolby Vision Engine on everything I watch. It’s pretty sweet.
With regular HDR10, it’s fine…proper colors,etc. It’s just with HLG files (granted, there aren’t many of these files) that it over saturates and raises black levels.
(the media info on the files Im using are almost identical to what’s been posted)

Its similar to what happens if you encode SDR in Bt2020.
This is using a Hisense U8H.

OK. Once you mention DV my knowledge runs out. Too many variables.

You got that right…DV is a variable nightmare.

While the lower picture is a bit washed out, the upper one in person looks very broken. Dark areas are crushed to black, saturated colors appear extremely exaggerated or even clipped at maximum saturation.

That seems to be an acceptable solution. I haven’t compared the result directly with what my CXUHD produces, but colors and contrast appear approximately correct with no obvious defects.


1 Like