ISO/IEC TR 23091-4:2019
(Main)Information technology -- Coding-independent code points
Information technology -- Coding-independent code points
This document describes common industry representation practices for the usage of video signal type code points, as these properties are conveyed across video content production and distribution carriage systems.
Technologies de l'information -- Titre manque
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Standards Content (Sample)
TECHNICAL ISO/IEC TR
REPORT 23091-4
First edition
2019-08
Information technology — Coding-
independent code points —
Part 4:
Usage of video signal type code points
Reference number
ISO/IEC TR 23091-4:2019(E)
©
ISO/IEC 2019
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ISO/IEC TR 23091-4:2019(E)
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ISO/IEC TR 23091-4:2019(E)
Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Abbreviated terms . 2
5 Overview . 4
6 Workflow domains . 5
7 Common video signal type combinations. 6
7.1 General . 6
7.2 Colorimetry and colour range descriptions . 7
7.2.1 General. 7
7.2.2 Colour properties . 7
7.2.3 Common descriptions and carriage – standard dynamic range video with
narrow colour gamut . 9
7.2.4 Common descriptions and carriage – standard dynamic range video with
wide colour gamut .10
7.2.5 Common descriptions and carriage – high dynamic range video with wide
colour gamut .11
7.3 Mastering display colour volume descriptions .12
7.3.1 Mastering display colour volume properties .12
7.3.2 Common descriptions and carriage – mastering display colour volume
descriptions . .13
Bibliography .15
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ISO/IEC TR 23091-4:2019(E)
Foreword
ISO (the International Organization for Standardization) and IEC (the International Electrotechnical
Commission) form the specialized system for worldwide standardization. National bodies that
are members of ISO or IEC participate in the development of International Standards through
technical committees established by the respective organization to deal with particular fields of
technical activity. ISO and IEC technical committees collaborate in fields of mutual interest. Other
international organizations, governmental and non-governmental, in liaison with ISO and IEC, also
take part in the work.
The procedures used to develop this document and those intended for its further maintenance are
described in the ISO/IEC Directives, Part 1. In particular, the different approval criteria needed for
the different types of document should be noted. This document was drafted in accordance with the
editorial rules of the ISO/IEC Directives, Part 2 (see www .iso .org/directives).
Attention is drawn to the possibility that some of the elements of this document may be the subject
of patent rights. ISO and IEC shall not be held responsible for identifying any or all such patent
rights. Details of any patent rights identified during the development of the document will be in the
Introduction and/or on the ISO list of patent declarations received (see www .iso .org/patents) or the IEC
list of patent declarations received (see http: //patents .iec .ch).
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
For an explanation of the voluntary nature of standards, the meaning of ISO specific terms and
expressions related to conformity assessment, as well as information about ISO's adherence to the
World Trade Organization (WTO) principles in the Technical Barriers to Trade (TBT) see www .iso
.org/iso/foreword .html.
This document was prepared by ISO/IEC JTC 1, Information technology, Subcommittee SC 29, Coding
of audio, picture, multimedia and hypermedia information in collaboration with ITU-T. The technically
identical text is published as ITU-T Series H Supplement 19 (03/2019).
A list of all parts in the ISO/IEC 23091 series can be found on the ISO website.
Any feedback or questions on this document should be directed to the user’s national standards body. A
complete listing of these bodies can be found at www .iso .org/members .html.
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ISO/IEC TR 23091-4:2019(E)
Introduction
This document discusses video signal property description code points and their combinations that
are widely used in production and video content workflows. Video properties and values are usually
expressed in "metadata" that can exist across production and distribution workflows. Knowledge of
these properties and their combinations has value as content is processed in the end-to-end production-
to-distribution workflow chain.
The combinations of all possible expressible video properties as code point values could hypothetically
result in hundreds or thousands of permutations; but many of those combinations are rarely or
never used in practice. For example, it is highly unlikely that perceptual quantization (PQ) transfer
characteristics function specified in Rec. ITU-R BT.2100 would be combined with the colour primaries
specified in Rec. ITU-R BT.601. Only a small subset of the possible combinations is used in practice.
This document is intended to help the producers of various content processing tools to avoid processing
mistakes that can cause video quality degradation due to having incorrect assumptions made about
video property combinations. There are only a few limited sets of video property combinations that
are widely used in present-day video production and distribution equipment chains. This document
describes these limited sets of combinations that are currently widely used and describes how the
associated signal type metadata is carried to aid in the automation of content workflows across
various domains of capture, production and distribution. Lastly, this document aims to help its readers,
especially toolset developers, to repurpose tools to work properly across several domains (e.g., capture,
production, production distribution, and service distribution) where similar video conversion functions
(e.g., chroma sub-sampling or colour space conversions) may be performed.
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TECHNICAL REPORT ISO/IEC TR 23091-4:2019(E)
Information technology — Coding-independent code
points —
Part 4:
Usage of video signal type code points
1 Scope
This document describes common industry representation practices for the usage of video signal type
code points, as these properties are conveyed across video content production and distribution carriage
systems.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content
constitutes requirements of this document. For dated references, only the edition cited applies. For
undated references, the latest edition of the referenced document (including any amendments) applies.
Rec. ITU-T H.264 | ISO/IEC 14496-10, Information technology — Coding of audio-visual objects — Part 10:
Advanced video coding
Rec. ITU-T H.265 | ISO/IEC 23008-2, Information technology — High efficiency coding and media delivery
in heterogeneous environments — High efficiency video coding
Rec. ITU-T H.273 | ISO/IEC 23091-2, Information technology — Coding-independent code points — Part
2: Video
3 Terms and definitions
For the purposes of this document, the terms and definitions in Rec. ITU-T H.265 | ISO/IEC 23008-2,
Rec. ITU-T H.264 | ISO/IEC 14496-10 and Rec. ITU-T H.273 | ISO/IEC 23091-2 and the following apply.
ISO ad IEC maintain terminological databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at http: //www .iso .org/obp
— IEC Electropedia: available at http: //www .electropedia .org
3.1
colour volume
space of all colours and intensities that a device or signal can reproduce or convey
3.2
creative intent
desired vision of the content creator who adjusts and approves the appearance of rendered content in
the production process
Note 1 to entry: Examples of a content creator are a director, cinematographer, videographer, editor or colourist.
3.3
electro-optical transfer function
EOTF
function to map a non-linear video signal to display linear light
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ISO/IEC TR 23091-4:2019(E)
3.4
full range
range in a fixed-point (integer) representation that spans the full range of values that could be expressed
with that bit depth
3.5
inverse electro-optical transfer function
inverse EOTF
function that is the inverse of an EOTF (3.3)
3.6
narrow range
range in a fixed-point (integer) representation that does not span the full range of values that could be
expressed with that bit depth
Note 1 to entry: Narrow range is, in some applications, referred to by synonyms such as: “limited range”, “video
range”, “legal range”, “SMPTE range” or “standard range”.
3.7
opto-electrical transfer function
OETF
function to map relative scene linear light to a non-linear video signal
3.8
opto-optical transfer function
OOTF
function to map relative scene linear light to display linear light
3.9
random access point access unit
RAPAU
access unit in a video bitstream containing an intra-coded picture with the property that all pictures
following the intra-coded picture in output order can be correctly decoded without using any
information preceding it in the bitstream
3.10
transfer function
function among any of the following: EOTF (3.3), inverse EOTF (3.5), OETF (3.7), inverse OETF, OOTF
(3.8), or inverse OOTF
4 Abbreviated terms
2K informally used to refer to an HD resolution (1920 × 1080 for television or 2048 × 1080
for film)
4K informally used to refer a UHD resolution (3840 × 2160 for television or 4096 × 2160 for film)
8K informally used to refer to a UHD resolution (7680 × 4320 or 8192 × 4320)
AVC advanced video coding (Rec. ITU-T H.264 | ISO/IEC 14496-10)
CICP coding-independent code points (Rec. ITU-T H.273 | ISO/IEC 23091-2)
GBR green, blue and red component colour system in linear light domain; same as RGB, although
emphasizing that the green component is handled as the primary colour component by some
technical elements of the video coding technology
NOTE The colour representation does not indicate the media component order in a coded
representation. For example, GBR represents the same component colour system as RGB.
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ISO/IEC TR 23091-4:2019(E)
G′B′R′ green, blue and red component colour system in a non-linear domain associated with a transfer
function which maps the linear light domain to a more perceptually uniform domain; same
as R′G′B′, although emphasizing that the green component is handled as the primary colour
component by some technical elements of the video coding technology
NOTE The colour representation does not indicate the media component order in a coded
representation. For example, G′B′R′ represents the same component colour system as R′G′B′.
HD high definition
HDR high dynamic range
HEVC high efficiency video coding (Rec. ITU-T H.265 | ISO/IEC 23008-2)
HLG hybrid log-gamma (as defined in Rec. ITU-R BT.2100)
HVS human visual system
LCD liquid crystal display
LED light-emitting diode
LUT look-up table
MDCV mastering display colour volume
MXF material exchange format (as defined in SMPTE ST 377-1)
N/A not applicable
N/R not required
NCG narrow colour gamut (typically as per Rec. ITU-R BT.709)
NCL non-constant luminance
OLED organic light-emitting diode
PQ perceptual quantizer (as defined in Rec. ITU-R BT.2100)
QP quantization parameter
RGB red, green and blue component colour system in linear light domain
NOTE The colour representation does not indicate the media component order in a coded
representation. For example, RGB represents the same component colour system as GBR.
R′G′B′ red, green and blue component colour system in a non-linear domain associated with a transfer
function which maps the linear light domain to a more perceptually uniform domain
NOTE The colour representation does not indicate the media component order in a coded
representation. For example, R′G′B′ represents the same component colour system as G′B′R′.
SD standard definition
SDR standard dynamic range
SEI supplemental enhancement information
UHD ultra-high definition
UL universal label (as defined in SMPTE ST 377-1)
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ISO/IEC TR 23091-4:2019(E)
VUI video usability information (a sequence-level syntax structure in HEVC and AVC bit-
streams)
WCG wide colour gamut (a gamut substantially wider than the gamut conveyed by Rec. ITU-R
BT.709, e.g., as per Rec. ITU-R BT.2020 or Rec. ITU-R BT.2100)
XYZ CIE 1931 colour space (wherein Y corresponds to the luminance signal)
Y′CbCr luma (Y′), chroma blue (Cb) and chroma red (Cr) colour representation defined by a matrix
transformation relationship to an R′G′B′ colour system
NOTE A Y′CbCr representation is commonly used for video/image distribution as a way of
encoding RGB information. Such a representation is also commonly expressed as YCbCr, Y′C C , or
B R
Y′C′ C′ , and can also be known as YUV in some documents. The relationship between Y′CbCr and
B R
R′G′B′ considered in this document is defined by matrix coefficients specified in Rec. ITU-R BT.601,
Rec. ITU-R BT.709, Rec. ITU-R BT.2020 or Rec. ITU-R BT.2100. Unlike the CIE-Y component in the
linear-light XYZ representation, the non-linear, the approximately perceptual uniform Y′ in this
representation might not be representing true luminance, regardless of the transfer function.
5 Overview
This document discusses video signal property description code points and their combinations that
are widely used in production and video content workflows. Video properties and values are usually
expressed in "metadata" that can exist across production and distribution workflows. Knowledge of
these properties and their combinations has value as content is processed in the end-to-end production-
to-distribution workflow chain.
The combinations of all possible expressible video properties as code point values could hypothetically
result in hundreds or thousands of permutations; but many of those combinations are rarely or
never used in practice. For example, it is highly unlikely that perceptual quantization (PQ) transfer
characteristics function specified in Rec. ITU-R BT.2100 would be combined with the colour primaries
specified in Rec. ITU-R BT.601. Only a small subset of the possible combinations is used in practice.
This document is written to provide information to help the producers of various content processing
tools to avoid processing mistakes that can cause video quality degradation due to having incorrect
assumptions made about video property combinations. There are only a few limited sets of video
property combinations that are widely used in present-day video production and distribution equipment
chains. This document describes these limited sets of combinations that are currently widely used
and describes how the associated signal type metadata is carried to aid in the automation of content
workflows across various domains of capture, production and distribution. Lastly, this document aims
to help its readers, especially toolset developers, to repurpose tools to work properly across several
domains (e.g., capture, production, production distribution, and service distribution) where similar
video conversion functions (e.g., chroma subsampling or colour space conversions) may be performed.
The coding-independent code points (CICP) specification for video (Rec. ITU-T H.273 | ISO/IEC 23091-2)
defines code points and fields that identify some properties of video signals. These are defined
independently from how these properties are carried in a coded video-layer bitstream such as an HEVC
or AVC bitstream, which could differ depending on bitstream format. The compressed representation
is sometimes considered to be a temporary, compacted state for distribution or delivery of the video
signal, while the reconstructed video signal output from a video decoder may be interpreted as having
the same meaning as a video signal immediately prior to compression by a compression encoder.
Subclauses 7.2 and 7.3 define system identifier tags combinations of the described commonly used
values of such video signal property combinations that apply across domains. In addition, these
subclauses also identify how the video property values are carried in the signal processing workflow.
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6 Workflow domains
Figure 1 illustrates workflow domains (capture, production, production distribution and service
distribution) in which video content may exist, be edited or be converted. Typical content workflows
across these domains are theatrical/scripted TV or live events. There are many similar video
processing functions that can be performed in each domain and often these may be repeated in the
next successive domain.
Figure 1 — Video workflows through different carriage domains
In the capture domain, content is created through sensors on cameras converting optical signals into a
digital format. Content is retained at its highest informational format, although some conversions may
be performed to reduce transport bandwidth demands.
In the interface to the production domain, content undergoes further processing transformations
such as non-linear transformations, chroma subsampling (e.g., 4:4:4 to 4:2:2), colour representation
changes (e.g., RGB to Y′CbCr NCL), and bit depth reduction (e.g., 16 bits per sample to 10 bits per
sample). For theatrical/scripted TV workflows entering in the production domain, content can be
added to by computer-generated imagery sources, overlaid with graphics, and colour graded using a
mastering display. For live event workflows, there is always a real-time constraint, which limits content
processing to real-time operations. After the colour grading, both static and dynamic metadata may
be generated that are to be attached to the content workflow. However, for live events, the generation
of highly customized metadata may not be practical, and metadata may need to be generated further
downstream by automated content analysis approaches.
In the production distribution domain, some additional processing is done to the content to further
reduce transport bandwidth demands. This may include some sample-wise processing transformations
(chroma subsampling and bit depth) and compression (e.g., using HEVC or AVC) but mostly employing
spatial compression techniques.
For 4:2:0 chroma subsampling operations, it is important to make known the relative location
alignment of the initial subsampling location processing of the content to avoid unnecessary quality
degradation upon further content processing. For purposes of this document, this property is described
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ISO/IEC TR 23091-4:2019(E)
in terms of the ChromaLocType variable as defined in HEVC, which further corresponds with the value
of the syntax elements chroma_sample_loc_type_top_field and chroma_sample_loc_type_bottom_field
in HEVC and AVC. For NCG material, the usual alignment corresponds to ChromaLocType equal to 0
(vertically interstitial). For WCG material, the usual alignment corresponds to ChromaLocType equal to
2 (co-sited).
At the service distribution domain, the content version in the workflow is in final form, though the
presentation of it may have some additional overlay graphics. Content processing at this interface
continues to reduce signal information to address transport bandwidth distribution demands while
still maximizing perceptual optimizations to retain content video quality. Operations reduce the
content to a 4:2:0 Y′CbCr 8 or 10 bit compressed stream using HEVC, AVC, or even Rec. ITU-T H.262
| ISO/IEC 13818-2 for the compression representation. This content workflow then finishes by the
content being distributed to the customer through broadcast, multicast, or unicast approaches and
then being presented for viewing.
Many of the content processing operations may employ multiple third-party content processing tools.
Currently most such tools are designed and operate within a specific domain with general assumptions
of how content was handled in the preceding domain. Tools may also have further constraints
depending on the content resolutions (e.g., HD or UHD). Some applications restrict the utilized colour
volume to be smaller than that of a full Rec. ITU-T BT.2020 and Rec. ITU-T BT.2100 container, such
as the smaller P3D65 colour gamut (as specified in SMPTE ST 2113) and intensity range of common
mastering or reference displays used in content production and delivery presentations. The approved
colour volume is often indicated with SMPTE ST 2086 metadata. Over time, it is expected that WCG
and/or HDR applications will evolve to use more of the available container colour volume.
7 Common video signal type combinations
7.1 General
This subclause enumerates common combinations of video properties and values that are currently
used within the content industry. Common methods of conveying video property information are
also described for the capture, production, production distribution, and service distribution carriage
domains.
System identifier tags are provided in this document to succinctly identify each commonly used
combination. Such system identifier tags may be used as out of band metadata for conversion tools,
and by production/distribution teams, to identify the workflow path needed to process and distribute
content.
Content conversion tools need the locations and values of stream properties and metadata values
associated with the corresponding system identifier. In some cases, the information to identify and
locate video properties of the stream information are described in a specific coded video stream
specification.
For example, SMPTE MXF structured streams indicate parameters and values through universal label
(UL) structures located in MXF headers. Such ULs are a set of registered labels maintained by SMPTE
(at registry.smpte-ra.org). An MXF UL structure is a 16-byte structure comprised of a UL Header [4
bytes-“0”] (per SMPTE ST 298), a UL Designator [4 bytes-“0”] (per SMPTE ST 336), and an Item
Designator [8 bytes-“000”] (per SMPTE ST 335, SMPTE ST 395, and SMPTE ST 2003). SMPTE MXF sub-
tables provide these 16-byte labels in addition to any values associated with the label.
As another example, HEVC or AVC bitstreams indicate parameters and values through VUI and SEI
constructs at the sequence parameter set level.
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7.2 Colorimetry and colour range descriptions
7.2.1 General
Colour volume information can describe combinations of video properties that are needed to convert
between colour volumes. Such conversions may include changes in bit depth, changes in colour
subsampling, non-linear optimizations, and may also include transformations based on carriage
and bit rate restrictions. SD, HD, and UHD material are typically associated with certain colorimetry
properties as indicated in Table 1, but this information can be carried in different places or may be
inferred depending on the storage or streaming format.
Table 1 — SD, HD and UHD video colorimetry properties
Colour Light Container space properties
Gamut Primaries Dynamic Transfer Colour Integer 4:2:0 chroma sample
Tag
Range function Rep- code location alignment
resenta- level (ChromaLocType)
tion scaling
HD or NCG BT.601 SDR BT.709 Y′CbCr Narrow Vertically interstitial
BT601_525
SD (ChromaLocType = 0)
Y′CbCr Narrow Vertically interstitial
BT601_625
(ChromaLocType = 0)
BT.709 Y′CbCr Narrow Vertically interstitial
BT709_YCC
(ChromaLocType = 0)
BT709_RGB R′G′B′ Narrow N/A
FR709_RGB R′G′B′ Full N/A
UHD WCG BT.2020 Y′CbCr Narrow Co-sited
BT2020_YCC_NCL
(ChromaLocType = 2)
BT2020_RGB R′G′B′ Narrow N/A
FR2020_RGB R′G′B′ Full N/A
BT.2100 HDR PQ Y′CbCr Narrow Co-sited
BT2100_PQ_YCC
(ChromaLocType = 2)
BT2100_PQ_RGB R′G′B′ Narrow N/A
HLG Y′CbCr Narrow Co-sited
BT2100_HLG_YCC
(ChromaLocType = 2)
BT2100_HLG_RGB R′G′B′ Narrow N/A
In this document, as in various industry groups such as UltraHD Forum, EBU, and DVB, UHD applications
are considered as those having at least one major property greater than HD (Rec. ITU-R BT.709), such
as colour gamut, resolution, dynamic range, or frame rate (e.g., 1080p60 HDR/WCG is considered UHD
herein).
Carriage formats for colour properties in each domain (capture, production, production distribution,
and service distribution) contain the same payload but in different wrappers. In the capture and
production domains, the colour property information can be carried in an MXF wrapper using a
generic picture essence descriptor as specified by SMPTE ST 2067-21:2016, Annex C. Colour volume
information in the distribution domain can be carried within the video stream as syntax information
in the selected video format such as HEVC, AVC, or MPEG-2 through VUI or equivalent syntax. The full
and narrow range scaling video property is not carried explicitly in all technologies and may need to be
taken implicitly or through a system identifier. In common practice, Y′CbCr colour representation uses
narrow range scaled levels.
7.2.2 Colour properties
For colorimetry and range scaling descriptions, the video properties described in Table 2 ordinarily
apply. Remarks on common usage are included in the table.
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