Commonly (mis)used terms and their meaning in the professional video context. This best effort list is maintained by the EBU Video Systems group. Suggestions and corrections are welcome via: tech@ebu.ch.
2K
Informally used to refer to a UHD resolution:
- For HDTV: 1920 x 1080
- For cinema: 2048 x 1080
Although 2k has been used to refer to the cinema resolution and 2K to the UHDTV one, this convention is not always followed. Further note that the cinema and television formats differ in other respects, such as framerate (e.g. 24 and 48 Hz for cinema).
4K
Informally used to refer to a UHD resolution:
- For UHDTV: 3840 x 2160
- For cinema: 4096 x 2160
The term is often used for product marketing. Although 4k has been used to refer to the cinema resolution and 4K to the UHDTV one, this convention is not always followed. Further note that the cinema and television formats differ in other respects, such as framerate (e.g. 24 and 48 Hz for cinema) and colour space (DCI-P3).
8K
Informally used to refer to a UHD resolution:
- For UHDTV: 7680 x 4320
- For cinema: 8192 x 4320
The term is often used for product marketing. Although 8k has been used to refer to the cinema resolution and 8K to the UHDTV one, this convention is not always followed. 8K is part of UHD-2. The first 8K service on-air is provided by the Japanese Public Broadcasting Corporation NHK, which uses the term "Super Hi-Vision" (SHV). Note that the aspect ratio of 8K television is the same as HDTV and UHD-1: 16:9.
ADM
Audio Definition Model
ADM is an XML schema which can give a complete technical description of the audio within a file to allow it to be correctly rendered. A simple stereo file will have two tracks with descriptions of what left and right channels are; whereas a complex object-based audio file with have descriptions for each object so they can be rendered correctly.
The ADM is described in ITU-R BS.2076. A tutorial about how to use ADM is available here.
Audio elements
There are three types of audio elements: channel-based, scene-based and object-based, each with unique attributes.
The Guidelines for the use of the ITU-R ADM Renderer (ITU-R Report BS.2466) provides a description of each type:
Channel-based: the format essentially used for today’s audio: mono, stereo, and multichannel sound systems, where signals correspond to positions of reproduction loudspeakers, and can be fed directly to them.
Object-based: where sound ‘objects’ are recorded, and the mixing and panning information is recorded with them, but not applied until the sound is reproduced.
Scene-based: where sound is recorded in standard directional patterns that can be transformed to any desired reproduction geometry. This is also known in its basic form as ‘Ambisonics’ recording, though a more developed form, Higher Order Ambisonics (HOA), is also used.
Bit depth (Quantisation)
The number of brightness or colour steps a pixel can be expressed in.
With greater bit depths, grey and colour gradients can be expressed with more detail.
Example: 10 bit means there are 210 = 1024 quantised levels.
Note that the bit depth used in the video chain typically goes from larger to smaller. E.g. a camera may internally handle images in 14-bit, output them in 10-bit and they may be distributed in 8-bit.
Standard Dynamic Range (SDR) typically used an 8-bit colour bit depth. HDR requires a bit depth of 10 or even 12 bits.
Colour gamut
The range of colours a specific device can (re)produce.
Also see: Colour Space
Colour space
The range of all colours that can be expressed by a certain system.
The larger a colour space, the more colours it can express.
There are different mathematical representations and conversions for the individual colour spaces (CIE Lab, CIE Luv, etc.). Colour spaces relevant for TV systems are defined in ITU-R BT.709 and ITU-R BT.2020 (Wide Colour Gamut).
Dynamic Range
Difference in brightness between the brightest and darkest image (element) that can be expressed.
Often used for scenes or objects in a scene.
EOTF
Electro-Optical Transfer Function
Characteristic curve of a display device, which defines the conversion of the (incoming) video signal to the (output) light.
Formerly known as "monitor gamma" (see ITU-R BT.1886 for the definition of the HDTV EOTF).
Frame Rate
Number of frames displayed per second.
Commonly used in Europe are: 25 Hz, 50 Hz and 100 Hz.
Note that interlaced television has a frame rate that is half its field rate. The EBU notation always uses the frame rate. Example: 1080i/25 (EBU notation) in many product specifications is called 1080i50 (using the field rate!).
HD
High Definition
HDMI
High Definition Multimedia Interface
Audio-video interface in the consumer domain, which supports the transport of UHD content.
HDR
High Dynamic Range
Describes the ability of a television system to produce, transmit and display a higher contrast range and in particular a higher peak luminance. As a result, more details can be displayed in dark and bright areas of the picture.
HDR-TV
This term has been introduced in the specification ITU-R BT.2100 and defines the interaction of increased spatial resolution (1080p, 2160p, 4320p), Wide Colour Gamut ITU-R BT.2020, better motion portrayal (up to 100 or 120 Hz) and the use of HDR (HLG or PQ).
HDR10
Term used mainly in the CE industry (e.g. Blu-rayTM) for video material:
- with a High Dynamic Range (HDR)
- using 10-bit quantisation
- using the Perceptual Quantization (PQ) HDR EOTF (standardized in SMPTE ST 2084)
- using the ITU-R BT.2020 Wide Colour Gamut
- providing static metadata: MaxFALL and MaxCLL (according to SMPTE ST 2086)
HEVC
High Efficiency Video Coding
Successor of ITU-T H.264 (= MPEG4 Part 10, AVC).
HEVC is a joint standard of the ITU Video Coding Experts Group (VCEG) and the ISO/IEC MPEG. HEVC is also known as ITU-T H.265, ISO/IEC 23008-2 or MPEG-H Part 2 HEVC. It is the same standard in terms of content, only the names/numbers differ, as they depend on the respective standardization committee.
HFR
High Frame Rate
Term for a frame rate of more than 50 progressive frames/second (50 Hz).
With the development of UHD two high frame rates were specified: 100 Hz (for 50 Hz countreis) and 120 Hz (for 60 Hz countries).
In the cinema sector, 48 Hz is already considered to be HFR.
HLG
Hybrid Log-Gamma
HDR camera characteristic (Opto-Electrical Transfer Function OETF) developed by the BBC and NHK. HLG is specified in ITU-R BT.2100 and ARIB STD-B67 (ARIB is a Japanese standards body).
The goal in the development of HLG was backward compatibility with SDR (full backwards compatibility requires the same colour space to be used).
HLG10
Defined by the Ultra HD Forum, indicating the use of:
- HLG, as specified in ITU-R BT.2100
- 10-bit quantization
- The ITU-R BT.2020 Wide Colour Gamut
ICtCp
Constant Intensity singal format, defined in ITU-R BT.2100.
ITU
International Telecommunication Union
A specialized agency of the United Nations that is responsible for issues that concern information and communication technologies. It sets worldwide standards ("Recommendations") for those technologies.
ITU-R BT.2020
ITU Recommendation that defines the (red, green and blue) colour primaries and Wide Colour Gamut for UHDTV.
In 2016, the ITU-R BT.2020 colour space was integrated into ITU-R BT.2100 and the 1080p resolution was added.
ITU-R BT.2100
ITU Recommendation providing the definition and related image parameters of the two High Dynamic Range technologies:
- Hybrid Log-Gamma (HLG)
- Perceptual Quantisation (PQ)
ITU-R BT.2100 by definition includes the ITU-R BT.2020 Wide Colour Gamut and the corresponding dynamic range parameters
ITU-R BT.709
ITU Recommendation that defines the (red, green and bleu) colour primaries and colour space for HDTV and the OETF for SDR.
MGA
Metadata Guided Audio
When audio is accompanied by metadata to ensure it is correctly handled and processed throughout the chain, including production, broadcast/streaming and the reproduction to the user.
NGA
Next Generation Audio
Personalization that allows users to optimize the sound experience according to their needs. Improved intelligibility, preferred dialogue language selection, immersiveness, flexibility and compatibility with headphones and a multitude of speaker layouts are among the features that characterize a personalized sound experience.
The key to enabling these features are:
1. Metadata, which is sent alongside the content to describe the intended audio experience as completely as possible
2. NGA codecs: MPEG-H 3D Audio, AC-4, DTS-UHD.
Nit
Alternative name for cd/m², used for luminance.
According to the International System of Units (SI) the unit to use is cd/m².
OETF
Opto-Electronic Transfer Function
Characteristic curve of the camera, which defines the conversion of light into an electric (nowadays: digital) signal. This was formerly known as "camera gamma", e.g. defined in ITU-R BT.709 for HDTV (SDR) and in ITU-R BT.2100 for HDR-TV.
OOTF
Opto-Optical Transfer Function
The overall transfer function which describes the overall system gamma from camera to display (includes the OETF and EOTF).
PCM
Pulse Code Modulation
It is a method used to digitally represent analogue samples.
PQ
Perceptual quantisation
Display transfer function (EOTF) defined in ITU-R BT.2100 (and in SMPTE ST 2084). PQ covers a very wide brightness range and uses defined digital values. The size of the quantization steps is adapted to the limit of perception of brightness differences in the Human Visual System (HVS).
PQ10
Defined by the Ultra HD Forum indicating the use of:
- PQ, as defined in ITU-R BT.2100
- 10-bit quantization
- The ITU-R BT.2020 Wide Colour Gamut
- No metadata
RGB
Colour component system in which the values for red, green and blue are expressed in the linear light domain.
R'G'B'
Colour component system in which the values for red, green and blue are expressed in a non-linear domain.
A transfer function is used to map linear RGB values to non-linear ones, with the aim of having better perceptual uniformity.
S-ADM
Serial-ADM
It is the serial presentation of the ADM designed for use in live real-time applications (e.g. broadcasting, streaming applications).
S-ADM is defined in ITU-R BS.2125
SD
Standard Definition
SDR
Standard Dynamic Range
The camera characteristic (OETF) for SDR is defined in ITU-R BT.709 and in ITU-R BT.2020, the corresponding monitor characteristic (EOTF) is specified in ITU-R BT.1886.
SMPTE
Society of Motion Picture and Television Engineers
An international organisation and standards committee in the area of video- and film technology. Many UHD-related standards have been developed in the SMPTE.
Spatial Resolution
Number of horizontal and vertical pixels, i.e. the number of pixels of a defined area with a certain aspect ratio. Examples:
- HDTV: 1280 x 720 (progressive)
- HDTV: 1920 x 1080 (interlaced or progressive)
- UHDTV: 3840 x 2160 (progressive)
- UHDTV: 7680 x 4320 (progressive)
Transfer function
A transfer characteristic defines how a signal is converted into another signal.
Probably the most important transfer functions in video are the OETF and the EOTF. See:
- ITU-R BT.2100 for HDR (HLG and PQ);
- ITU-R BT.709 and ITU-R BT.2020 for SDR gamma
UHDTV (EBU)
Ultra High Definition Television
Natural evolution of the High Definition Television System television system to a higher fidelity television standard.
Note that the EBU defines UHDTV to include one or more of the following:
- Better resolution (4K)
- High Dynamic Range (HDR)
- Wide Colour Gamut (WCG)
- High Frame Rates (HFR)
- Next Generation Audio (NGA)
UHDTV (ITU)
Ultra High Definition Television
Television system defined in ITU-R BT.2020. This includes:
- Higher resolution (4x or 16x HDTV resolution)
- Better motion portrayal (up to 100 or 120 Hz)
- Extended colour space ITU-R BT.2020
- SDR (so no HDR!)
UHDTV-1, UHD-1
Ultra High Definition with a resolution of 2160 lines with 3840 pixels each and a fixed aspect ratio of 16:9.
UHD-1 corresponds to four times the HD signal (1080x1920) and is colloquially referred to as 4K.
UHDTV-2, UHD-2
Ultra High Definition with a resolution of 4320 lines of 7680 pixels each and a fixed aspect ratio of 16:9.
HD-2 corresponds to 16 times the HD signal (1080x1920). UHD-2 is also colloquially known as 8K.
UHD Phase 1
Term from the DVB/EBU phase model (2013).
Compared to 'normal' HDTV, the spatial resolution is increased to 2160p/50 and the colour space widened to ITU-R BT.2020.
UHD Phase 2
Term from the DVB/EBU phase model (2013)
On top of UHD-1 now also HDR and HFR are added, uisng various 'conformance points'.
Y'CbCr
Colour representation that can be obtained from R'G'B' by a matrix transformation.
Splitting into Luma (Y') and Chroma (Cb, Cr) components allows for exploiting the lower HVS sensitivity for chroma detail than for luma detail, such as is used in, for example, 4:2:2 colour subsampling.
XYZ
CIE 1931 colour space.