HLG (hybrid log-gamma)
HLG (hybrid log-gamma) is a royalty-free HDR video format developed by the BBC and NHK for broadcast and live TV. HLG needs no metadata, and a single HLG signal looks acceptable on both HDR and standard dynamic range screens. This makes HLG well suited to live sports and events, where producing separate HDR and SDR feeds is costly.
Why it matters
HLG lets live sports and event streamers offer HDR without producing and sending two separate feeds. That saves production and delivery cost. The trade-off is less precise control than metadata-based formats, and colors may shift on older screens that only understand Rec. 709.
How it works
- The camera signal is recorded with the HLG curve, which mixes a standard curve for darker tones with a log curve for highlights.
- No metadata is needed, so the signal can be switched and edited like normal live video.
- An HDR screen reads the full curve and shows the brighter highlights.
- A standard screen reads the lower part as normal video and shows a watchable picture.
HLG vs HDR10: what is the difference?
HLG needs no metadata and can play on standard screens, while HDR10 uses static metadata and needs an HDR display. That makes HLG better for live broadcast and HDR10 more common for on-demand films and series. Both use Rec. 2020 colors and 10-bit video.
Does YouTube support HLG?
Yes. YouTube accepts HDR uploads that use either the PQ or HLG transfer function with Rec. 2020 colors, and it creates a standard dynamic range version automatically for devices without HDR. That makes HLG a practical choice for creators who record HDR on cameras or phones that output HLG.
Where it's used
Broadcasters and live sports streamers use HLG to deliver HDR live events with one feed that also works on standard TVs. Video platforms meet it in uploads from phones and cameras.
By the numbers
- HLG was jointly developed by the BBC and NHK, approved as ARIB STD-B67 in 2015 and included in ITU-R BT.2100 in 2016. (Wikipedia: Hybrid log-gamma)
- YouTube accepts HDR uploads using either the PQ or HLG transfer function. (YouTube Help: Upload High Dynamic Range (HDR) videos)
