HLG (Hybrid Log-Gamma) – HDfury Vertex glossary
The broadcast HDR format from BBC and NHK, and the Vertex settings that advertise or send it.
HLG (Hybrid Log-Gamma) is a type of HDR made for TV broadcasts by the BBC and NHK.
It is designed so one signal looks acceptable on normal TVs and brighter on HDR TVs.
Unlike HDR10, it does not need extra brightness information sent with the picture.
Does the HDfury Vertex support HLG?
YESYes. Automix has an [HLG] flag that makes the EDID advertise HLG, and HLG is one of the EOTF choices in the custom HDR generator. Your display must support HLG itself (p.28, p.32).
How to use it with the Vertex:
- Put the EDID in Automix mode (slide switch or GUI) and tick [HLG] (p.8, p.28).
- RS232: #set edidhlg on; IR: vertex_edidhlgon (p.50, p.76).
- When not forced, the EDID follows what the connected sinks support (p.50).
- For testing, choose EOTF 'HLG ITU-R BT.2100-0' in the custom HDR generator (p.32).
What it is
HLG (Hybrid Log-Gamma) is an HDR transfer function developed by the BBC and NHK and standardised in ITU-R BT.2100. It is mainly used for broadcast and live TV.
Unlike HDR10, HLG does not need static metadata such as MaxCLL. The lower part of its curve is close to a normal SDR gamma, which keeps the picture watchable on many SDR displays.
On the Vertex
In Automix mode the [HLG] flag forces the Automix EDID to present HLG support (p.28). RS232: #set edidhlg on/off; when not forced, the EDID follows the sink capabilities (p.50). IR: vertex_edidhlgon/off (p.76).
In the custom HDR metadata generator, HLG ITU-R BT.2100-0 is one of the EOTF choices, next to SMPTE ST 2084 and the SDR/HDR luminance ranges (p.32).
Common questions
Is HLG the same as HDR10?
No. HDR10 uses the PQ (SMPTE ST 2084) curve plus static metadata; HLG uses a different curve and needs no such metadata. Both are defined in ITU-R BT.2100.
My source does not offer HLG through the Vertex. What can I do?
In Automix mode, tick the [HLG] flag so the EDID advertises HLG support (p.28), or use RS232 #set edidhlg on (p.50). The display itself must still support HLG.
Where do I actually see HLG?
Mostly in live broadcasts and some streaming apps, for example sports or BBC programmes.