Hybrid Log-Gamma (HLG) is a high dynamic range (HDR) standard that was jointly developed by the BBC and NHK. The HLG standard is royalty-free and was approved as ARIB STD-B67 by the Association of Radio Industries and Businesses (ARIB). HLG is compatible with standard dynamic range (SDR) displays. HLG is defined in ATSC 3.0, Digital Video Broadcasting (DVB) UHD-1 Phase 2, and International Telecommunication Union (ITU) Rec. 2100. HLG is supported by HDMI 2.0b, HEVC, VP9, and H.264/MPEG-4 AVC. HLG is supported by video services such as BBC iPlayer, DirecTV, Freeview Play, and YouTube.
- where E is the signal normalized by the reference white level and E' is the resulting nonlinear signal
- where r is the reference white level and has a signal value of 0.5
- where a = 0.17883277, b = 0.28466892, and c = 0.55991073
The signal value is 0.5 for the reference white level while the signal value for 1 has a relative luminance that is 12 times higher than the reference white level. ARIB STD-B67 has a nominal range of 0 to 12. HLG uses a logarithmic curve for the upper half of the signal values due to Weber's law.
HLG does not need to use metadata since it is compatible with both SDR displays and HDR displays. HLG can be used with displays of different brightness in a wide range of viewing environments.
The dynamic range that can be perceived by the human eye in a single image is around 14 stops. An SDR video display with a 2.4 gamma curve and a bit depth of 8-bits per sample can display a range of about 6 stops without visible banding. Professional SDR video displays with a bit depth of 10-bits per sample extend that range to about 10 stops. When HLG is displayed on a 2,000 cd/m2 display with a bit depth of 10-bits per sample it can display a range of 200,000:1 or 17.6 stops without visible banding.
HLG increases the dynamic range of the video compared to a conventional gamma curve by using a logarithmic curve for the upper half of the signal values. HLG also increases the dynamic range by not including the linear part of the conventional gamma curve used by Rec. 601 and Rec. 709. The linear part of the conventional gamma curve was used to limit camera noise in low light video but is no longer needed with HDR cameras.
HLG is supported in HEVC with a formula that is mathematically equivalent to ARIB STD-B67 but has a nominal range of 0 to 1 instead of 0 to 12:
- where Lc has a nominal range of 0 to 1 and V is the resulting nonlinear signal
- where a = 0.17883277, b = 0.28466892, and c = 0.55991073
On October 27, 2015, Colorfront announced that their Transkoder 2016 software would support HDR output using HLG.
On December 3, 2015, Harmonic Inc. and NASA announced the HDR capture of a Atlas V launch which was broadcast the next day on NASA TV using HLG. UHDTV HDR video clips will be published early next year in both HDR10 and HLG.
On April 15, 2016, Dome Productions announced that they will begin trials of HLG to deliver HDR content.
On April 18, 2016, the Ultra HD Forum announced their guidelines for UHD Phase A which includes support for HLG. The Ultra HD Forum also defined HLG10 as HLG, a bit depth of 10-bits, and the Rec. 2020 color space.
On August 3, 2016, Sony announced that in October they will release a firmware update to add HLG to their BVM-X300 OLED monitor.
On September 14, 2016, Sony announced that their VPL-VW675ES projector will support HLG.
On November 17, 2016, the Digital Video Broadcasting (DVB) Steering Board approved UHD-1 Phase 2 with a HDR solution which supports Hybrid Log-Gamma (HLG) and Perceptual Quantizer (PQ). The specification has been published as DVB Bluebook A157 and will be published by the ETSI as TS 101 154 v2.3.1.
On November 18, 2016, Mediapro/Overon announced that they will transmit the Spanish Football League (LFP) worldwide using 4K HDR broadcasts based in HLG
On December 25, 2016, Atomos updated their Shogun Inferno product to include HLG input and output for recording, monitoring editing and layout from Cameras and computers as well as to HLG compatible TV's.
On January 10, 2017, LG Corporation announced that they will add support for HLG to their 2016 OLED TVs and their 2016 Super UHD TVs with a firmware update.
On January 16, 2017, Sony announced that they will add support for HLG to their 2017 4K TVs with a firmware update.
On February 17, 2017, Panasonic announced that they will add support for HLG to several models of their 2016 4K TVs with a firmware update.
On May 31, 2017, Sony began releasing firmware updates for several of their 2016 and 2017 Android TV models which adds support for HLG.
On November 27, 2017, Panasonic began releasing firmware updates for several of their 2016 TV models which adds support for HLG.
On December 5, 2017, the BBC announced that Blue Planet II would be available in 4K HDR on the BBC iPlayer using HLG. Blue Planet II will be available on the BBC iPlayer service from December 10, 2017 to January 16, 2018. The BBC states that almost 400 TV models have support for HLG which includes TV models from Finlux, Hisense, Hitachi, LG, Panasonic, Philips, Samsung, Sony, and Toshiba.
- Dynamic range
- Gamma correction
- High-dynamic-range rendering
- High-dynamic-range imaging
- High-dynamic-range video
- "High Dynamic Range" (PDF). European Broadcasting Union. Retrieved 2015-11-01.
- "High Dynamic Range with Hybrid Log-Gamma" (PDF). BBC. Retrieved 2015-11-08.
- "ARIB STD-B67" (PDF). Association of Radio Industries and Businesses. 2015-07-03. Retrieved 2015-11-01.
- "BT.2100 : Image parameter values for high dynamic range television for use in production and international programme exchange". International Telecommunication Union. 2016-07-04. Retrieved 2016-07-04.
- "DVB SB Approves UHD HDR Specification". Digital Video Broadcasting. 2016-11-17. Retrieved 2017-01-07.
- "ATSC Standard: Video" (PDF). Advanced Television Systems Committee. 2017-05-19. Retrieved 2017-05-19.
- "Introducing HDMI 2.0b". HDMI.org. Retrieved 2017-01-07.
- Rajan Joshi; Shan Liu; Gary Sullivan; Gerhard Tech; Jizheng Xu; Yan Ye (2015-09-05). "HEVC Screen Content Coding Draft Text 4". JCT-VC. Retrieved 2015-11-01.
- "HDR Video Playback". Android. Retrieved 2016-09-23.
- "ITU-T Recommendation H.264 (04/2017)". ITU. 2017-04-13. Retrieved 2017-06-14.
- "Upload High Dynamic Range (HDR) videos". Google. Retrieved 2017-01-11.
- Julian Clover (2016-09-23). "Freeview updates for HEVC and Ultra HD". Broadband TV News. Retrieved 2016-09-23.
- Leo Kelion (2017-12-05). "Blue Planet II comes to iPlayer in 4K HDR". BBC. Retrieved 2017-12-05.
- Jason Dachman (2017-12-14). "AT&T DirecTV To Deliver First Live 4K HDR Telecast in U.S. With Tonight's Penguins-Golden Knights Game". Sportsvideo. Retrieved 2018-01-10.
- Greg Tarr (2017-12-15). "DirecTV Presents NHL 4K Game With Live HDR, But Was Anyone Watching?". HDGuru. Retrieved 2018-01-10.
- T. Borer; A. Cotton. "A "Display Independent" High Dynamic Range Television System" (PDF). BBC. Retrieved 2015-11-01.
- Rajan Joshi; Shan Liu; Gary Sullivan; Gerhard Tech; Ye-Kui Wang; Jizheng Xu; Yan Ye (2016-03-24). "HEVC Screen Content Coding Draft Text 6". JCT-VC. Retrieved 2016-03-26.
- "Study Group Report High-Dynamic-Range (HDR) Imaging Ecosystem". Society of Motion Picture and Television Engineers. Retrieved 2015-11-30.
- "ITU announces BT.2100 HDR TV standard". Rasmus Larsen. 2016-07-05. Retrieved 2016-07-26.
- Simon Thompson (2015-05-15). "High Dynamic Range at the SES Industry Days". BBC. Retrieved 2015-11-01.
- Y. Nishida; T. Yamashita; A. Ichigaya; T. Shimizu (2015-06-09). "Proposed addition of transfer characteristics in VUI". JCT-VC. Retrieved 2015-11-01.
- "Sony Describes Hybrid Log Gamma (HLG) at SMPTE 2015 Event". DisplayDaily. Retrieved 2015-11-03.
- "SMPTE 2015 Annual Technical Conference & Exhibition". Society of Motion Picture and Television Engineers. Retrieved 2015-11-03.
- "Colorfront spotlights amazing UHD HDR performance at SMPTE 2015". American City Business Journals. 2015-10-27. Retrieved 2015-11-01.
- Chris Forrester (2015-11-04). "SkyPerfect offers UHD-HDR by DTH". Advanced Television. Retrieved 2015-11-04.
- Vincent Teoh (2015-11-06). "LG Talk Up 4K OLED TV & HDR at UK Briefing". HDTVtest. Retrieved 2015-11-08.
- "NASA and Harmonic Explore the Boundaries of UHD at ISS Resupply Launch at Kennedy Space Center". CNN. 2015-12-03. Archived from the original on 2015-12-08. Retrieved 2015-12-05.
- ""Huge success" for UHD-HLG test in Rome". Advanced Television. 2015-12-14. Retrieved 2015-12-18.
- Brian Hallett (2015-12-23). "DaVinci Resolve 12.2 Update & Price Drop". Pro Video Coalition. Retrieved 2015-12-23.
- "LEADER Announces 12G SDI, HDR and Video over IP Options for its LV 5490 and LV 5480 4K-capable Waveform Monitors". CreativeCOW.net. 2016-01-12. Retrieved 2016-01-13.
- Wim Van den Broeck (2016-03-11). "How Avid is Advancing Key Industry Trends Highlighted at the HPA Tech Retreat 2016". Avid Technology. Retrieved 2016-04-04.
- Bryant Frazer (2016-01-29). "Avid Media Composer 8.5 Adds HDR, Simplifies Menus, Offers Better Feedback on the Timeline". studiodaily. Retrieved 2016-04-04.
- "Harmonic Showcases Innovation for Agile Video Delivery at 2016 NAB Show". Yahoo! Finance. 2016-03-29. Retrieved 2016-04-11.
- "Canon reveals new camera and lens in advance of NAB". RedShark. 2016-04-13. Retrieved 2016-04-13.
- "Dome Productions to Begin Trialing of HLG for Delivering HDR". Yahoo! Finance. 2016-04-15. Retrieved 2016-04-15.
- "Sony Goes Beyond Definition at NAB 2016". PR Newswire. 2016-04-18. Retrieved 2016-04-18.
- "Ultra HD Forum Releases First Industry Guidelines for Deploying End-to-End Live & Pre-Recorded UHD Services in 2016". Business Wire. 2016-04-18. Retrieved 2016-04-18.
- "End-to-end guidelines for phase A implementation". Ultra HD Forum. 2016-04-18. Retrieved 2016-04-18.
- Colin Mann (2016-07-29). "4K HDR from SKY Perfect JSAT". Advanced Television. Retrieved 2016-07-30.
- Bryant Frazer (2016-08-03). "Sony to Update BVM-X300 4K Monitor in October". studiodaily. Retrieved 2016-08-07.
- "IBC 2016: Eutelsat fast forwards in the video age". Eutelsat. 2016-09-07. Retrieved 2016-09-07.
- Ramus Larsen (2016-09-07). "Android TV 7.0 supports Dolby Vision, HDR10 and HLG". flatpanelshd. Retrieved 2016-09-23.
- "Sony Electronics Announces the Latest Addition to its 4K HDR Home Theater Projector Line-Up at CEDIA 2016". PR Newswire. 2016-09-14. Retrieved 2016-09-23.
- Steve May (2016-11-04). "Hybrid Log-Gamma: Why it's the next big thing in 4K TV". Trusted Reviews. Retrieved 2017-01-10.
- Steven Robertson (2016-11-07). "True colors: adding support for HDR videos on YouTube". Google. Retrieved 2017-01-11.
- James Grover (2016-11-17). "UHD-1 Phase 2 approved". TVBEurope. Retrieved 2017-01-07.
- Dave Bevan (2016-12-08). "BBC announces arrival of HLG content on its iPlayer IPTV platform". BBC. Retrieved 2016-12-08.
- Ramus Larsen (2016-12-12). "HDMI 2.0b standard gets support for HLG HDR". flatpanelshd. Retrieved 2017-01-07.
- Andrew Cotton (2016-12-31). "2016 in Review - High Dynamic Range". BBC. Retrieved 2017-01-07.
- Ogy Stoilov (2016-12-25). "Atomos Shogun Inferno Firmware 8.1 Unlocks Sony FS 2K/Raw Super-Slow Motion". 4K Shooters. Retrieved 2017-01-10.
- John Archer (2017-01-03). "LG Takes Aim At Samsung With New 'Quantum Dot-Beating' TV Technology". Forbes. Retrieved 2017-01-07.
- Matt Burgess (2017-01-04). "Panasonic launches 'world's first' HDR, ultra-HD OLED TV". Wired. Retrieved 2017-01-07.
- John Archer (2017-01-04). "Sony Unveils Debut OLED TV Range". Forbes. Retrieved 2017-01-07.
- "Eutelsat scales up Ultra HD content with two new channels at the popular Hotbird neighbourhood". Eutelsat. 2017-01-04. Retrieved 2017-01-14.
- "New JVC 4K e-Shift4 Projectors Deliver Higher Brightness and Contrast, Add Low Latency Mode". JVC. 2017-01-05. Retrieved 2017-01-16.
- Ramus Larsen (2017-01-04). "LG will bring HLG HDR to 2016 OLED & LCDs through firmware update". flatpanelshd. Retrieved 2017-01-07.
- Ramus Larsen (2017-01-16). "Sony: Android TV 7.0 coming to 2017, 2016 & 2015 TVs". flatpanelshd. Retrieved 2017-01-16.
- Ramus Larsen (2017-02-17). "Panasonic will add HLG HDR support to select 2016 TVs". flatpanelshd. Retrieved 2017-03-04.
- Ramus Larsen (2017-03-13). "Philips: HLG HDR update coming to 2016 TVs". flatpanelshd. Retrieved 2017-03-13.
- "The Latest (and Greatest!) for Premiere Pro CC and Media Encoder". Adobe Systems. 2017-04-19. Retrieved 2017-04-20.
- Ramus Larsen (2017-05-31). "Android 7.0 will roll out to Sony TVs starting May 31". flatpanelshd. Retrieved 2017-05-31.
- Daron James (2017-09-28). "Panasonic Releases GH5 Firmware 2.0 with Anamorphic and More". No Film School. Retrieved 2017-12-09.
- Ramus Larsen (2017-11-27). "Panasonic releases HLG HDR update for select 2016 TVs". flatpanelshd. Retrieved 2017-12-05.
- "How can I watch Blue Planet II in Ultra HD on my connected TV?". BBC. 2017-12-05. Retrieved 2017-12-06.
- Bruno Ferreira (2017-12-06). "Qualcomm lifts the veil on the Snapdragon 845 SoC". Tech Report. Retrieved 2017-12-09.
- Brittany Hillen (2017-12-14). "Final Cut Pro X 10.4 adds HDR support, VR video editing, and (finally!) curves". DPReview. Retrieved 2017-12-17.
- "Vizio courts cord cutters, challenges OLED, and adds new HDR options to its 2018 smart TV lineup". TechHive. Retrieved 2018-10-26.
- "Pansonic S1, S1R to ship in march, HLG photo and high res mode added to feature list". DpReview news. Retrieved 2019-01-10.