Rec. 2100
{{short description|ITU-R recommendation}}
ITU-R Recommendation BT.2100, more commonly known by the abbreviations Rec. 2100 or BT.2100, introduced high-dynamic-range television (HDR-TV) by recommending the use of the perceptual quantizer (PQ [SMPTE ST 2084]) or hybrid log–gamma (HLG) transfer functions instead of the traditional "gamma" previously used for SDR-TV.{{Cite web|last=|first=|date=|title=BT.2100 : Image parameter values for high dynamic range television for use in production and international programme exchange|url=https://www.itu.int/rec/R-REC-BT.2100/en|archive-url=|archive-date=|access-date=2021-02-04|website=www.itu.int}}{{Cite web|last=|first=|date=|title=BT.1886 : Reference electro-optical transfer function for flat panel displays used in HDTV studio production|url=https://www.itu.int/rec/R-REC-BT.1886/en|archive-url=|archive-date=|access-date=2021-02-04|website=www.itu.int}}
It defines various aspects of HDR-TV such as display resolution (HDTV and UHDTV), frame rate, chroma subsampling, bit depth, color space, color primaries, white point, and transfer function.{{cite news|url=https://www.itu.int/rec/R-REC-BT.2100|title=BT.2100 : Image parameter values for high dynamic range television for use in production and international programme exchange|date=2018-07-12|access-date=2019-01-05|publisher=International Telecommunication Union}}{{cite news |title=ITU announces BT.2100 HDR TV standard |publisher=Rasmus Larsen |url=http://www.flatpanelshd.com/news.php?subaction=showfull&id=1467719709 |date=2016-07-05 |access-date=2016-07-26 | work = FlatpanelsHD }} It was posted on the International Telecommunication Union (ITU) website on July 4, 2016. Rec. 2100 uses a wide color gamut (WCG) which is the same as Rec. 2020's.
Technical details
= Transfer functions =
{{See also|Transfer functions in imaging}}
Rec. 2100 defines two sets of HDR transfer functions which are perceptual quantization (PQ) and hybrid log-gamma (HLG). HLG is supported in Rec. 2100 with a nominal peak luminance of 1,000 cd/m2 and a system gamma value that can be adjusted depending on background luminance. For a reference viewing environment the peak luminance of display should be 1000 cd/m2 or more for small area highlights and the black level should be 0.005 cd/m2 or less. The surround light should be 5 cd/m2 and be neutral grey at standard illuminant D65.
Within each set, the documented transfer functions include an:
- electro-optical transfer function (EOTF) which maps the non-linear signal value into display light
- opto-optical transfer function (OOTF) which maps relative scene linear light to display linear light
- opto-electronic transfer function (OETF) which maps relative scene linear light into the non-linear signal value
=System colorimetry=
{{Further|Rec. 2020#System colorimetry}}
File:CIExy1931_Rec_2020.svg showing the Rec. 2100 (HDR-TV) color space in the triangle and the location of the primary colors. Rec. 2100 uses Illuminant D65 for the white point.]]
Rec. 2100 uses the same color primaries as Rec. 2020 which is a Wide Color Gamut.
| class="wikitable" |
| rowspan="2" |Color space
! colspan="2" |White point ! colspan="6" |Primary colors |
|---|
| xW
!yW !xR !yR !xG !yG !xB !yB |
| align="center" |ITU-R BT.2100
|0.3127 |0.3290 |0.708 |0.292 |0.170 |0.797 |0.131 |0.046 |
=Resolution=
Rec. 2100 specifies three resolutions of 1920 × 1080 ("Full HD"), 3840 × 2160 ("4K UHD"), and 7680 × 4320 ("8K UHD"). These resolutions have an aspect ratio of 16:9 and use square pixels.
=Frame rate=
Rec. 2100 specifies the following frame rates: 120p, 119.88p, 100p, 60p, 59.94p, 50p, 30p, 29.97p, 25p, 24p, 23.976p. Only progressive scan frame rates are allowed.
=Digital representation=
Rec. 2100 specifies a bit depth of either 10-bits per sample or 12-bits per sample, with either narrow range or full range color values. A future-use and intermediate linear RGB format using IEEE 16 bit floating point representation for each channel is also specified. For narrow range color, 10-bit per sample signals use video levels where the black level is defined as 64, achromatic gray level as 512 and the nominal peak as 940 in RGB, Y, and I encoding and 960 in Cb/Cr, and Ct/Cp component encoding. 12-bit per sample signals define 256 as the black level, 2048 as the gray level and the nominal peak is 3760 in RGB, Y, and I component encoding and 3840 in Cb/Cr, and Ct/Cp component encoding. Narrow range signals may extend below black or above peak white (super-black and super-white respectively), but must always be clipped to the signal range of 4-1019 for 10-bit signals or 16-4079 for 12-bit signals.
=Signal formats=
Rec. 2100 specifies the use of RGB, YCbCr, and ICtCp. ICtCp provides an improved color representation that is designed for high dynamic range (HDR) and wide color gamut signals (WCG).{{cite news |title=ICtCp Dolby White Paper |publisher=Dolby |url=http://www.dolby.com/us/en/technologies/dolby-vision/ICtCp-white-paper.pdf |access-date=2016-04-20}}
=Luma coefficients=
Rec. 2100 allows for RGB, YCbCr, and ICtCp signal formats with 4:4:4, 4:2:2, and 4:2:0 chroma subsampling. Rec. 2100 specifies that if a luma (Y') signal is made that it use the same matrix coefficients as Rec. 2020: 0.2627 for red, 0.678 for green, and 0.0593 for blue (derived from BT.2020 primaries and white point).
= Chroma sample location =
{{Unreferenced Section|date=July 2022}}
Before Rec. BT.2020 the chroma sample location that was in use was center left. But in H.265 (2018-02) top-left chroma siting was mandated for BT.2020-2 and BT.2100-1, that must be described in VUI (video usability information) as such. First value of VUI should be 2 for top-left chroma and 0 for center left. Blu-ray also uses top-left chroma for HDR, including for Dolby Vision.
References
{{Reflist}}
External links
- [https://www.itu.int/rec/R-REC-BT.2100 ITU-R Recommendation BT.2100]
- [https://www.itu.int/pub/R-REP-BT.2390 ITU-R BT.2390] – A Report by ITU providing background information on HDR in general, and for the perceptual quantization (PQ) and hybrid log–gamma (HLG) HDR signal parameters specified in the Rec.2100
{{Dynamic range color representation}}
{{Color space}}
Category:Film and video technology
Category:ITU-R recommendations
Category:Audiovisual introductions in 2016