ISO/IEC 23091-2:2021
(Main)Information technology — Coding-independent code points — Part 2: Video
Information technology — Coding-independent code points — Part 2: Video
This document defines various code points and fields that establish properties of a video (or still image) representation and are independent of the compression encoding and bit rate. These properties can describe the appropriate interpretation of decoded data or can, similarly, describe the characteristics of such a signal before the signal is compressed by an encoder that is suitable for compressing such an input signal.
Technologies de l'information — Points de code indépendants du codage — Partie 2: Vidéo
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INTERNATIONAL ISO/IEC
STANDARD 23091-2
Second edition
2021-10
Information technology — Coding-
independent code points —
Part 2:
Video
Technologies de l'information — Points de code indépendants du
codage —
Partie 2: Vidéo
Reference number
ISO/IEC 23091-2:2021(E)
© ISO/IEC 2021
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ISO/IEC 23091-2:2021(E)
COPYRIGHT PROTECTED DOCUMENT
© ISO/IEC 2021
All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may
be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting on
the internet or an intranet, without prior written permission. Permission can be requested from either ISO at the address below
or ISO’s member body in the country of the requester.
ISO copyright office
CP 401 • Ch. de Blandonnet 8
CH-1214 Vernier, Geneva
Phone: +41 22 749 01 11
Email: copyright@iso.org
Website: www.iso.org
Published in Switzerland
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ISO/IEC 23091-2:2021(E)
Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Abbreviated terms . 2
5 Conventions . 2
5.1 Arithmetic operators . 2
5.2 Bit-wise operators . 3
5.3 Assignment operators . 3
5.4 Relational, logical, and other operators . 3
5.5 Mathematical functions . 4
5.6 Order of operations . 5
6 Specified code points.6
7 Principles for definition and referencing of code points . 6
7.1 Application usage . 6
7.2 Code point encoding and defaults . 6
7.3 Externally defined values . 7
7.4 Reference format . 7
7.5 Uniform resource name format . 7
8 Video code points . 7
8.1 Colour primaries . 7
8.2 Transfer characteristics . 9
8.3 Matrix coefficients .12
8.4 Video frame packing type . 18
8.5 Packed video content interpretation . 24
8.6 Sample aspect ratio . 24
8.7 Chroma 4:2:0 sample location type . 25
Bibliography .29
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ISO/IEC 23091-2:2021(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 or
www.iec.ch/members_experts/refdocs).
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 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. In the IEC, see www.iec.ch/understanding-standards.
This document was prepared by Joint Technical Committee ISO/IEC JTC1, Information technology,
Subcommittee SC 29, Coding of audio, picture, multimedia and hypermedia information, in collaboration
with ITU-T [as Rec. ITU-T H.273 (07/2021)].
This second edition cancels and replaces the first edition (ISO/IEC 23091-2:2019), which has been
technically revised.
The main changes are as follows:
— the addition of a code point for chroma sampling grid alignment indication for the 4:2:0 colour
format;
— correction of the range of values specification for sample aspect ratio indication;
— correction of the formulae for the IC C colour representation for the hybrid-log-gamma (HLG)
T P
transfer function specified in Rec. ITU-R BT.2100-2;
— correction of the formulae for the transfer function for the sYCC colour representation specified in
IEC 61966-2-1.
A list of all parts in the ISO/IEC 23091 series can be found on the ISO and IEC websites.
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 and
www.iec.ch/national-committees.
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ISO/IEC 23091-2:2021(E)
Introduction
In a number of specifications, there is a need to identify some characteristics of video (or still image)
media content that are logically independent of the compression format. These characteristics can
include, for example, aspects that relate to the sourcing or presentation, or the role of the video (or still
image) media component. These characteristics have typically been documented by fields that take an
encoded value or item selected from an enumerated list, herein called code points.
These code points are typically defined in the specification of compression formats to document these
characteristics of the media. In past practices, the definition of these fields has been copied from
document to document, sometimes with new values being added in later documents (and sometimes
with later amendments specified to add new entries to existing documents).
This past practice has raised a number of issues, including the following:
a) A lack of a formal way to avoid conflicting assignments being made in different documents.
b) Having additional values defined in later specifications that can be practically used with older
compression formats, but without clear formal applicability of these new values to older documents.
c) Any update or correction of code point semantics can incur significant effort to update all
documents in which the code point is specified, instead of enabling a single central specification to
apply across different referencing specifications.
d) The choice of reference for other specifications (such as container or delivery formats) not being
obvious; wherein a formal reference to a compression format document appears to favour that one
format over others, and also appears to preclude definitions defined in other compression format
specifications.
e) Burdensome maintenance needs to ensure that a reference to material defined in a compression
format specification is maintained appropriately over different revisions of the referenced format
specification, as the content of a compression format specification can change over time and is
ordinarily not intended as a point of reference for defining such code points.
This document provides a central definition of such code points for video and image applications
to address these issues. This document can be used to provide universal descriptions to assist
interpretation of video and image signals following decoding, or to describe the properties of these
signals before they are encoded.
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INTERNATIONAL STANDARD ISO/IEC 23091-2:2021(E)
Information technology — Coding-independent code
points —
Part 2:
Video
1 Scope
This document defines various code points and fields that establish properties of a video (or still image)
representation and are independent of the compression encoding and bit rate. These properties can
describe the appropriate interpretation of decoded data or can, similarly, describe the characteristics
of such a signal before the signal is compressed by an encoder that is suitable for compressing such an
input signal.
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.
ISO/CIE 11664-1, Colorimetry — Part 1: CIE standard colorimetric observers
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
ISO and IEC maintain terminology databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at https:// www .electropedia .org/
3.1
bottom field
assembly of the odd-numbered rows of samples of the components (3.3) of a video frame using a
numbering of rows that starts with row number 0 as the top row
3.2
chroma
sample array or single sample representing one of the two colour difference signals related to the
primary colours, represented by the symbols Cb and Cr
Note 1 to entry: The term "chroma" is used rather than "chrominance" in order to avoid the implication of the use
of linear light transfer characteristics that is often associated with "chrominance".
3.3
component
array or single sample from one of the three arrays [luma (3.4) and two chroma (3.2)] that compose
a picture (3.5) in 4:2:0, 4:2:2, or 4:4:4 colour format or the array or a single sample of the array that
compose a picture in monochrome format
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ISO/IEC 23091-2:2021(E)
3.4
luma
sample array or single sample representing the monochrome signal related to the primary colours,
represented by the symbol or subscript Y or L
Note 1 to entry: The term "luma" is used rather than "luminance" in order to avoid the implication of the use of
linear light transfer characteristics that is often associated with "luminance". The symbol L is sometimes used
instead of the symbol Y to avoid confusion with the symbol y as used for vertical location.
3.5
picture
array of luma (3.4) samples in monochrome format or array of luma samples and two corresponding
arrays of chroma (3.2) samples in 4:2:0, 4:2:2, and 4:4:4 colour format
3.6
reserved
values of a particular code point that are for future use by ITU-T | ISO/IEC
Note 1 to entry: These values shall not be used in identifiers conforming to this edition of this document.
It is possible they will be used in a manner yet to be specified in some future extensions of this document by
ITU-T | ISO/IEC.
3.7
top field
assembly of the even-numbered rows of samples of a video frame using a numbering of rows that starts
with row number 0 as the top row
3.8
unspecified
values of a particular code point that have no specified meaning in this edition of this document and
will not have a specified meaning in the future as an integral part of future editions of this document
4 Abbreviated terms
LSB least significant bit
MSB most significant bit
5 Conventions
NOTE The mathematical operators used in this document are similar to those used in the C programming
language. However, integer division and arithmetic shift operations are specifically defined. Numbering and
counting conventions generally begin from 0.
5.1 Arithmetic operators
+ addition
− subtraction (as a two-argument operator) or negation (as a unary prefix operator)
* multiplication, including matrix multiplication
exponentiation, x to the power of y (in other contexts, such notation may be used for super-
y
x
scripting not intended for interpretation as exponentiation)
integer division with truncation of the result toward zero (for example, 7 / 4 and (−7) / (−4)
/
are truncated to 1 and (−7) / 4 and 7 / (−4) are truncated to −1)
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ISO/IEC 23091-2:2021(E)
÷ division in mathematical formulae where no truncation or rounding is intended
x
division in mathematical formulae where no truncation or rounding is intended
y
y
summation of f( i ) with i taking all integer values from x up to and including y
fi()
∑
ix=
x % y modulus, remainder of x divided by y, defined only for integers x and y with x >= 0 and y > 0
5.2 Bit-wise operators
bit-wise "and" (when operating on integer arguments, operates on a two's complement
representation of the integer value; when operating on a binary argument that contains fewer
&
bits than another argument, the shorter argument is extended by adding more significant
bits equal to 0)
bit-wise "or" (when operating on integer arguments, operates on a two's complement
representation of the integer value; when operating on a binary argument that contains fewer
|
bits than another argument, the shorter argument is extended by adding more significant
bits equal to 0)
bit-wise "exclusive or" (when operating on integer arguments, operates on a two's
complement representation of the integer value; when operating on a binary argument that
^
contains fewer bits than another argument, the shorter argument is extended by adding more
significant bits equal to 0)
arithmetic right shift of a two's complement integer representation of x by y binary digits
x >> y (defined only for non-negative integer values of y; bits shifted into the MSBs as a result of the
right shift have a value equal to the MSB of x prior to the shift operation)
arithmetic left shift of a two's complement integer representation of x by y binary digits (de-
x << y fined only for non-negative integer values of y; bits shifted into the LSBs as a result of the left
shift have a value equal to 0)
5.3 Assignment operators
= assignment operator
increment, i.e. x++ is equivalent to x = x + 1; when used in an array index, evaluates to the
++
value of the variable prior to the increment operation
decrement, i.e. x− − is equivalent to x = x − 1; when used in an array index, evaluates to the
− −
value of the variable prior to the decrement operation
increment by amount given, i.e. x += 3 is equivalent to x = x + 3, and x += (−3) is equivalent to
+=
x = x + (−3)
decrement by amount given, i.e. x −= 3 is equivalent to x = x − 3, and x −= (−3) is equivalent
−=
to x = x − (−3)
5.4 Relational, logical, and other operators
= = equality operator
!= not equal to operator
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ISO/IEC 23091-2:2021(E)
!x logical negation "not"
> larger than operator
< smaller than operator
>= larger than or equal to operator
<= smaller than or equal to operator
conditional/logical "and" operator, performs a logical "and" of its Boolean operators, but only
&&
evaluates the second operand when necessary
conditional/logical "or" operator, performs a logical "or" of its Boolean operators, but only
| |
evaluates the second operand when necessary
ternary conditional, if condition a is true, then the result is equal to b; otherwise the result
a ? b : c
is equal to c
NOTE When a relational operator is applied to a code point or variable that has been assigned the value
"na" (not applicable), the value "na" is treated as a distinct value for the code point or variable. The value "na" is
considered not to be equal to any other value.
5.5 Mathematical functions
Formulae (1) to (11) define functions for use in mathematical expressions within this document.
x; x >= 0
Absx = (1)
()
−x; x < 0
Ceil(x) the smallest integer greater than or equal to x. (2)
Clip1 ( x ) = Clip3( 0, ( 1 << BitDepth ) − 1, x ), (3)
Y Y
where BitDepth is the representation bit depth of the corresponding luma colour component signal.
Y
Clip1 ( x ) = Clip3( 0, ( 1 << BitDepth ) − 1, x ), (4)
C C
where BitDepth is the representation bit depth of the corresponding chroma colour component signal
C
C. In general, BitDepth may be distinct for different chroma colour components signals C – e.g. for C
C
corresponding to Cb or Cr.
x; z < x
Clip3x(), y, z = y; z > y (5)
z; otherwise
Floor( x ) the largest integer less than or equal to x. (6)
Ln( x ) the natural logarithm of x. (7)
Log10( x ) the base-10 logarithm of x. (8)
Round( x ) = Sign( x ) * Floor( Abs( x ) + 0.5 ). (9)
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ISO/IEC 23091-2:2021(E)
1; x > 0
Sign()x= 0; x = = 0 (10)
−1; x < 0
Sqrt( x ) the square root of x. (11)
5.6 Order of operations
When order of precedence in an expression is not indicated explicitly by use of parentheses, the
following rules apply:
— Operations of a higher precedence are evaluated before any operation of a lower precedence.
— Operations of the same precedence are evaluated sequentially from left to right.
Table 1 specifies the precedence of operations from highest to lowest; a higher position in the table
indicates a higher precedence.
NOTE For those operators that are also used in the C programming language, the order of precedence used
in this document is the same as used in the C programming language.
Table 1 — Operation precedence from highest (at top of table) to lowest (at bottom of table)
Operations (with operands x, y, and z)
"x++", "x− −"
"!x", "−x" (as a unary prefix operator)
y
"x "
x
"x * y", "x / y", "x ÷ y", " ", "x % y"
y
y
"x + y", "x − y" (as a two-argument operator), " fi() "
∑
ix=
"x << y", "x >> y"
"x < y", "x <= y", "x > y", "x >= y"
"x = = y", "x != y"
"x & y"
"x | y"
"x && y"
"x | | y"
"x ? y : z"
"x.y"
"x = y", "x += y", "x −= y"
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ISO/IEC 23091-2:2021(E)
6 Specified code points
This clause identifies the code points defined in this document, as listed in Table 2 with cross-references
to the subclause in which each is specified.
Table 2 — List of code point definitions
Name Abstract Subclause
ColourPrimaries Video colour primaries 8.1
TransferCharacteristics Video colour transfer characteristics 8.2
MatrixCoefficients and VideoFullRangeFlag Video matrix colour coefficients 8.3
VideoFramePackingType and QuincunxSamplingFlag Video frame packing 8.4
PackedContentInterpretationType Interpretation of packed video frames 8.5
SampleAspectRatio, SarWidth, and SarHeight Sample aspect ratio of video 8.6
Chroma sampling grid alignment for 8.7
Chroma420SampleLocType video fields or frames having the 4:2:0
colour format
7 Principles for definition and referencing of code points
7.1 Application usage
This document specifies code points for coding-independent description of video and image signal type
characteristics. These signal type identifiers can be used to provide universal descriptions to assist the
interpretation of signals following decoding or to describe properties of the signals prior to encoding.
An example of the usage of the code point identifiers specified in this document is illustrated in
Figure 1. The signal type identifier may be represented within the video elementary stream produced
by an encoder. Alternatively, or additionally, the signal type identifier may be carried outside of a video
elementary stream by other means, such as in a file storage format, in a system multiplex format, or in
a streaming system protocol.
Figure 1 — Example usage
7.2 Code point encoding and defaults
The code points defined herein may be specified as a value or a label of an enumerated list. The definition
of their encoding and representation (e.g. as a binary number) is the responsibility of the specification
using the code point, as is the identification of any applicable default value not specified herein. It is also
possible for external specifications to use a mapping to values defined here, if they wish to preserve
identical semantics but different code point assignments.
Guidance is given for each code point as to a suitable type (e.g. unsigned integer) and a suitable value
range (e.g. 0–63) for assistance in writing derived specifications. In some instances, default flag values
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ISO/IEC 23091-2:2021(E)
are provided that are suggested to be inferred for code point parameters with associated flags that
might not be explicitly signalled or specified in derived specifications.
7.3 Externally defined values
If the external specification permits values not defined by this document to be identified in the same
field that carries values defined by this document, then that other specification shall identify how
values defined herein can be distinguished from values not defined herein.
7.4 Reference format
References to code points in this document should use only the code point name (i.e. a "Name" from
Table 2) and specification title, and not use subclause numbers or any other "fragile" reference such as
a table number. For example, for a hypothetical code point named "ChocolateDensity", a document can
refer to "ChocolateDensity as defined in ISO/IEC 23091-2".
7.5 Uniform resource name format
ISO/IEC 23091-1 specifies a uniform resource name format that may be used for the code points
specified in this document.
8 Video code points
8.1 Colour primaries
Type: Unsigned integer, enumeration
Range: 0 – 255
ColourPrimaries indicates the chromaticity coordinates of the source colour primaries as specified
in Table 3 in terms of the CIE 1931 definition of x and y, which shall be interpreted as specified by ISO/
CIE 11664-1.
An 8-bit field should be adequate for representation of the ColourPrimaries code point.
Table 3 — Interpretation of colour primaries (ColourPrimaries) value
Value Colour primaries Informative remarks
0 Reserved For future use by ITU-T | ISO/IEC
1 primary x y Rec. ITU-R BT.709-6
green 0.300 0.600
Rec. ITU-R BT.1361-0 conventional colour gamut
system and extended colour gamut system
blue 0.150 0.060
(historical)
red 0.640 0.330
IEC 61966-2-1 sRGB or sYCC
white D65 0.3127 0.3290
IEC 61966-2-4
Society of Motion Picture and Television
Engineers RP 177 (1993) Annex B
2 Unspecified Image characteristics are unknown or are
determined by the application.
3 Reserved For future use by ITU-T | ISO/IEC
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ISO/IEC 23091-2:2021(E)
Table 3 (continued)
Value Colour primaries Informative remarks
4 primary x y Rec. ITU-R BT.470-6 System M (historical)
green 0.21 0.71
United States National Television System
Committee 1953 Recommendation for
blue 0.14 0.08
transmission standards for colour television
red 0.67 0.33
United States Federal Communications
white C 0.310 0.316
Commission Title 47 Code of Federal Regulations
(2003) 73.682 (a) (20)
5 primary x y Rec. ITU-R BT.470-6 System B, G (historical)
green 0.29 0.60
Rec. ITU-R BT.601-7 625
blue 0.15 0.06
Rec. ITU-R BT.1358-0 625 (historical)
red 0.64 0.33
Rec. ITU-R BT.1700-0 625 PAL and 625 SECAM
white D65 0.3127 0.3290
6 primary x y Rec. ITU-R BT.601-7 525
green 0.310 0.595
Rec. ITU-R BT.1358-1 525 or 625 (historical)
blue 0.155 0.070
Rec. ITU-R BT.1700-0 NTSC
red 0.630 0.340
Society of Motion Picture and Television
white D65 0.3127 0.3290
Engineers ST 170 (2004)
(functionally the same as the value 7)
7 primary x y Society of Motion Picture and Television
Engineers ST 240 (1999)
green 0.310 0.595
(functionally the same as the value 6)
blue 0.155 0.070
red 0.630 0.340
white D65 0.3127 0.3290
8 primary x y Generic film (colour filters using Illuminant C)
green 0.243 0.692 (Wratten 58)
blue 0.145 0.049 (Wratten 47)
red 0.681 0.319 (Wratten 25)
white C 0.310 0.316
9 primary x y Rec. ITU-R BT.2020-2
green 0.170 0.797
Rec. ITU-R BT.2100-2
blue 0.131 0.046
red 0.708 0.292
white D65 0.3127 0.3290
10 primary x y Society of Motion Picture and Television
Engineers ST 428-1 (2019)
green (Y) 0.0 1.0
(CIE 1931 XYZ as in ISO/CIE 11664-1)
blue (Z) 0.0 0.0
red (X) 1.0 0.0
centre white 1 ÷ 3 1 ÷ 3
11 primary x y Society of Motion Picture and Television
Engineers RP 431-2 (2011)
green 0.265 0.690
blue 0.150 0.060
red 0.680 0.320
white 0.314 0.351
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ISO/IEC 23091-2:2021(E)
Table 3 (continued)
Value Colour primaries Informative remarks
12 primary x y Society of Motion Picture and Te
...
INTERNATIONAL ISO/IEC
STANDARD 23091-2
Second edition
2021-09
Information technology — Coding-
independent code points —
Part 2:
Video
Technologies de l'information — Points de code indépendants du
codage —
Partie 2: Vidéo
PROOF/ÉPREUVE
Reference number
ISO/IEC 23091-2:2021(E)
©
ISO/IEC 2021
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ISO/IEC 23091-2:2021(E)
COPYRIGHT PROTECTED DOCUMENT
© ISO/IEC 2021
All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may
be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting
on the internet or an intranet, without prior written permission. Permission can be requested from either ISO at the address
below or ISO’s member body in the country of the requester.
ISO copyright office
CP 401 • Ch. de Blandonnet 8
CH-1214 Vernier, Geneva
Phone: +41 22 749 01 11
Email: copyright@iso.org
Website: www.iso.org
Published in Switzerland
ii PROOF/ÉPREUVE © ISO/IEC 2021 – All rights reserved
---------------------- Page: 2 ----------------------
ISO/IEC 23091-2:2021(E)
Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Abbreviated terms . 2
5 Conventions . 2
5.1 Arithmetic operators . 2
5.2 Bit-wise operators. 3
5.3 Assignment operators . 3
5.4 Relational, logical, and other operators. 4
5.5 Mathematical functions . 4
5.6 Order of operations . 5
6 Specified code points . 5
7 Principles for definition and referencing of code points . 6
7.1 Application usage . 6
7.2 Code point encoding and defaults . 6
7.3 Externally defined values . 7
7.4 Reference format . 7
7.5 Uniform resource name format . 7
8 Video code points . 7
8.1 Colour primaries . 7
8.2 Transfer characteristics . 9
8.3 Matrix coefficients.11
8.4 Video frame packing type .18
8.5 Packed video content interpretation .24
8.6 Sample aspect ratio .24
8.7 Chroma 4:2:0 sample location type .25
Bibliography .29
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ISO/IEC 23091-2:2021(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 or www .iec .ch/ members
_experts/ refdocs).
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 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. In the IEC, see www .iec .ch/ understanding -standards.
This document was prepared by Joint Technical Committee ISO/IEC JTC1, Information technology,
Subcommittee SC 29, Coding of audio, picture, multimedia and hypermedia information, in collaboration
with ITU-T (as ITU-T H.273 (12/2016)).
This second edition cancels and replaces the first edition (ISO/IEC 23091-2:2019), which has been
technically revised.
The main changes compared to the previous edition are as follows:
— the addition of a code point for chroma sampling grid alignment indication for the 4:2:0 colour
format;
— correction of the range of values specification for sample aspect ratio indication;
— correction of the formulae for the IC C colour representation for the hybrid-log-gamma (HLG)
T P
transfer function specified in Rec. ITU-R BT.2100-2;
— correction of the formulae for the transfer function for the sYCC colour representation specified in
IEC 61966-2-1.
A list of all parts in the ISO/IEC 23091 series can be found on the ISO and IEC websites.
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 and www .iec .ch/ national
-committees.
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ISO/IEC 23091-2:2021(E)
Introduction
In a number of specifications, there is a need to identify some characteristics of video (or still image)
media content that are logically independent of the compression format. These characteristics can
include, for example, aspects that relate to the sourcing or presentation, or the role of the video (or still
image) media component. These characteristics have typically been documented by fields that take an
encoded value or item selected from an enumerated list, herein called code points.
These code points are typically defined in the specification of compression formats to document these
characteristics of the media. In past practices, the definition of these fields has been copied from
document to document, sometimes with new values being added in later documents (and sometimes
with later amendments specified to add new entries to existing documents).
This past practice has raised a number of issues, including the following:
a) A lack of a formal way to avoid conflicting assignments being made in different documents.
b) Having additional values defined in later specifications that can be practically used with older
compression formats, but without clear formal applicability of these new values to older documents.
c) Any update or correction of code point semantics can incur significant effort to update all
documents in which the code point is specified, instead of enabling a single central specification to
apply across different referencing specifications.
d) The choice of reference for other specifications (such as container or delivery formats) not being
obvious; wherein a formal reference to a compression format document appears to favour that one
format over others, and also appears to preclude definitions defined in other compression format
specifications.
e) Burdensome maintenance needs to ensure that a reference to material defined in a compression
format specification is maintained appropriately over different revisions of the referenced format
specification, as the content of a compression format specification can change over time and is
ordinarily not intended as a point of reference for defining such code points.
This document provides a central definition of such code points for video and image applications
to address these issues. This document can be used to provide universal descriptions to assist
interpretation of video and image signals following decoding, or to describe the properties of these
signals before they are encoded.
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INTERNATIONAL STANDARD ISO/IEC 23091-2:2021(E)
Information technology — Coding-independent code
points —
Part 2:
Video
1 Scope
This document defines various code points and fields that establish properties of a video (or still image)
representation and are independent of the compression encoding and bit rate. These properties can
describe the appropriate interpretation of decoded data or can, similarly, describe the characteristics
of such a signal before the signal is compressed by an encoder that is suitable for compressing such an
input signal.
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.
ISO/CIE 11664-1, Colorimetry — Part 1: CIE standard colorimetric observers
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
ISO and IEC maintain terminological databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at http:// www .electropedia .org/
3.1
bottom field
assembly of the odd-numbered rows of samples of the components (3.3) of a video frame using a
numbering of rows that starts with row number 0 as the top row
3.2
chroma
sample array or single sample representing one of the two colour difference signals related to the
primary colours, represented by the symbols Cb and Cr
Note 1 to entry: The term "chroma" is used rather than "chrominance" in order to avoid the implication of the use
of linear light transfer characteristics that is often associated with "chrominance".
3.3
component
array or single sample from one of the three arrays [luma (3.4) and two chroma (3.2)] that compose
a picture (3.5) in 4:2:0, 4:2:2, or 4:4:4 colour format or the array or a single sample of the array that
compose a picture in monochrome format
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ISO/IEC 23091-2:2021(E)
3.4
luma
sample array or single sample representing the monochrome signal related to the primary colours,
represented by the symbol or subscript Y or L
Note 1 to entry: The term "luma" is used rather than "luminance" in order to avoid the implication of the use of
linear light transfer characteristics that is often associated with "luminance". The symbol L is sometimes used
instead of the symbol Y to avoid confusion with the symbol y as used for vertical location.
3.5
picture
array of luma (3.4) samples in monochrome format or array of luma samples and two corresponding
arrays of chroma (3.2) samples in 4:2:0, 4:2:2, and 4:4:4 colour format
3.6
reserved
values of a particular code point that are for future use by ITU-T | ISO/IEC
Note 1 to entry: These values shall not be used in identifiers conforming to this edition of this document.
It is possible they will be used in a manner yet to be specified in some future extensions of this document by
ITU-T | ISO/IEC.
3.7
top field
assembly of the even-numbered rows of samples of a video frame using a numbering of rows that starts
with row number 0 as the top row
3.8
unspecified
values of a particular code point that have no specified meaning in this edition of this document and
will not have a specified meaning in the future as an integral part of future editions of this document
4 Abbreviated terms
LSB least significant bit
MSB most significant bit
5 Conventions
NOTE The mathematical operators used in this document are similar to those used in the C programming
language. However, integer division and arithmetic shift operations are specifically defined. Numbering and
counting conventions generally begin from 0.
5.1 Arithmetic operators
+ addition
− subtraction (as a two-argument operator) or negation (as a unary prefix operator)
* multiplication, including matrix multiplication
exponentiation, x to the power of y (in other contexts, such notation may be used for super-
y
x
scripting not intended for interpretation as exponentiation)
integer division with truncation of the result toward zero (for example, 7 / 4 and (−7) / (−4)
/
are truncated to 1 and (−7) / 4 and 7 / (−4) are truncated to −1)
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ISO/IEC 23091-2:2021(E)
÷ division in mathematical formulae where no truncation or rounding is intended
x
division in mathematical formulae where no truncation or rounding is intended
y
y
summation of f( i ) with i taking all integer values from x up to and including y
fi()
∑
ix=
x % y modulus, remainder of x divided by y, defined only for integers x and y with x >= 0 and y > 0
5.2 Bit-wise operators
bit-wise "and" (when operating on integer arguments, operates on a two's complement
representation of the integer value; when operating on a binary argument that contains fewer
&
bits than another argument, the shorter argument is extended by adding more significant
bits equal to 0)
bit-wise "or" (when operating on integer arguments, operates on a two's complement
representation of the integer value; when operating on a binary argument that contains fewer
|
bits than another argument, the shorter argument is extended by adding more significant
bits equal to 0)
bit-wise "exclusive or" (when operating on integer arguments, operates on a two's
complement representation of the integer value; when operating on a binary argument that
^
contains fewer bits than another argument, the shorter argument is extended by adding more
significant bits equal to 0)
arithmetic right shift of a two's complement integer representation of x by y binary digits
x >> y (defined only for non-negative integer values of y; bits shifted into the MSBs as a result of the
right shift have a value equal to the MSB of x prior to the shift operation)
arithmetic left shift of a two's complement integer representation of x by y binary digits (de-
x << y fined only for non-negative integer values of y; bits shifted into the LSBs as a result of the left
shift have a value equal to 0)
5.3 Assignment operators
= assignment operator
increment, i.e. x++ is equivalent to x = x + 1; when used in an array index, evaluates to the
++
value of the variable prior to the increment operation
decrement, i.e. x− − is equivalent to x = x − 1; when used in an array index, evaluates to the
− −
value of the variable prior to the decrement operation
increment by amount given, i.e. x += 3 is equivalent to x = x + 3, and x += (−3) is equivalent to
+=
x = x + (−3)
decrement by amount given, i.e. x −= 3 is equivalent to x = x − 3, and x −= (−3) is equivalent
−=
to x = x − (−3)
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ISO/IEC 23091-2:2021(E)
5.4 Relational, logical, and other operators
= = equality operator
!= not equal to operator
!x logical negation "not"
> larger than operator
< smaller than operator
>= larger than or equal to operator
<= smaller than or equal to operator
conditional/logical "and" operator, performs a logical "and" of its Boolean operators, but only
&&
evaluates the second operand when necessary
conditional/logical "or" operator, performs a logical "or" of its Boolean operators, but only
| |
evaluates the second operand when necessary
ternary conditional, if condition a is true, then the result is equal to b; otherwise the result
a ? b : c
is equal to c
NOTE When a relational operator is applied to a code point or variable that has been assigned the value
"na" (not applicable), the value "na" is treated as a distinct value for the code point or variable. The value "na" is
considered not to be equal to any other value.
5.5 Mathematical functions
x; x >= 0
Absx()= (1)
−x; x < 0
Ceil(x) the smallest integer greater than or equal to x. (2)
Clip1 ( x ) = Clip3( 0, ( 1 << BitDepth ) − 1, x ), (3)
Y Y
where BitDepth is the representation bit depth of the corresponding luma colour component signal.
Y
Clip1 ( x ) = Clip3( 0, ( 1 << BitDepth ) − 1, x ), (4)
C C
where BitDepth is the representation bit depth of the corresponding chroma colour component signal
C
C. In general, BitDepth may be distinct for different chroma colour components signals C – e.g. for C
C
corresponding to Cb or Cr.
x; z < x
Clip3x(), y, z = y; z > y (5)
z; otherwise
Floor( x ) the largest integer less than or equal to x. (6)
Ln( x ) the natural logarithm of x. (7)
Log10( x ) the base-10 logarithm of x. (8)
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ISO/IEC 23091-2:2021(E)
Round( x ) = Sign( x ) * Floor( Abs( x ) + 0.5 ). (9)
1; x > 0
Sign()x= 0; x = = 0 (10)
−1; x < 0
Sqrt( x ) the square root of x. (11)
5.6 Order of operations
When order of precedence in an expression is not indicated explicitly by use of parentheses, the
following rules apply:
— Operations of a higher precedence are evaluated before any operation of a lower precedence.
— Operations of the same precedence are evaluated sequentially from left to right.
Table 1 specifies the precedence of operations from highest to lowest; a higher position in the table
indicates a higher precedence.
NOTE For those operators that are also used in the C programming language, the order of precedence used
in this document is the same as used in the C programming language.
Table 1 — Operation precedence from highest (at top of table) to lowest (at bottom of table)
Operations (with operands x, y, and z)
"x++", "x− −"
"!x", "−x" (as a unary prefix operator)
y
"x "
x
"x * y", "x / y", "x ÷ y", " ", "x % y"
y
y
"x + y", "x − y" (as a two-argument operator), " fi "
()
∑
ix=
"x << y", "x >> y"
"x < y", "x <= y", "x > y", "x >= y"
"x = = y", "x != y"
"x & y"
"x | y"
"x && y"
"x | | y"
"x ? y : z"
"x.y"
"x = y", "x += y", "x −= y"
6 Specified code points
This clause identifies the code points defined in this document, as listed in Table 2 with cross-references
to the subclause in which each is specified.
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ISO/IEC 23091-2:2021(E)
Table 2 — List of code point definitions
Name Abstract Subclause
ColourPrimaries Video colour primaries 8.1
TransferCharacteristics Video colour transfer characteristics 8.2
MatrixCoefficients and VideoFullRangeFlag Video matrix colour coefficients 8.3
VideoFramePackingType and QuincunxSamplingFlag Video frame packing 8.4
PackedContentInterpretationType Interpretation of packed video frames 8.5
SampleAspectRatio, SarWidth, and SarHeight Sample aspect ratio of video 8.6
Chroma sampling grid alignment for 8.7
Chroma420SampleLocType video fields or frames having the 4:2:0
colour format
7 Principles for definition and referencing of code points
7.1 Application usage
This document specifies code points for coding-independent description of video and image signal type
characteristics. These signal type identifiers can be used to provide universal descriptions to assist the
interpretation of signals following decoding or to describe properties of the signals prior to encoding.
An example of the usage of the code point identifiers specified in this document is illustrated in
Figure 1. The signal type identifier may be represented within the video elementary stream produced
by an encoder. Alternatively, or additionally, the signal type identifier may be carried outside of a video
elementary stream by other means, such as in a file storage format, in a system multiplex format, or in
a streaming system protocol.
Figure 1 — Example usage
7.2 Code point encoding and defaults
The code points defined herein may be specified as a value or a label of an enumerated list. The definition
of their encoding and representation (e.g. as a binary number) is the responsibility of the specification
using the code point, as is the identification of any applicable default value not specified herein. It is also
possible for external specifications to use a mapping to values defined here, if they wish to preserve
identical semantics but different code point assignments.
Guidance is given for each code point as to a suitable type (e.g. unsigned integer) and a suitable value
range (e.g. 0–63) for assistance in writing derived specifications. In some instances, default flag values
are provided that are suggested to be inferred for code point parameters with associated flags that
might not be explicitly signalled or specified in derived specifications.
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ISO/IEC 23091-2:2021(E)
7.3 Externally defined values
If the external specification permits values not defined by this document to be identified in the same
field that carries values defined by this document, then that other specification shall identify how
values defined herein can be distinguished from values not defined herein.
7.4 Reference format
References to code points in this document should use only the code point name (i.e. a "Name" from
Table 2) and specification title, and not use subclause numbers or any other "fragile" reference such as
a table number. For example, for a hypothetical code point named "ChocolateDensity", a document can
refer to "ChocolateDensity as defined in ISO/IEC 23091-2".
7.5 Uniform resource name format
ISO/IEC 23091-1 specifies a uniform resource name format that may be used for the code points
specified in this document.
8 Video code points
8.1 Colour primaries
Type: Unsigned integer, enumeration
Range: 0 – 255
ColourPrimaries indicates the chromaticity coordinates of the source colour primaries as specified
in Table 3 in terms of the CIE 1931 definition of x and y, which shall be interpreted as specified by
ISO/CIE 11664-1.
An 8-bit field should be adequate for representation of the ColourPrimaries code point.
Table 3 — Interpretation of colour primaries (ColourPrimaries) value
Value Colour primaries Informative remarks
0 Reserved For future use by ITU-T | ISO/IEC
1 primary x y Rec. ITU-R BT.709-6
green 0.300 0.600
Rec. ITU-R BT.1361-0 conventional colour gamut
system and extended colour gamut system
blue 0.150 0.060
(historical)
red 0.640 0.330
IEC 61966-2-1 sRGB or sYCC
white D65 0.3127 0.3290
IEC 61966-2-4
Society of Motion Picture and Television
Engineers RP 177 (1993) Annex B
2 Unspecified Image characteristics are unknown or are
determined by the application.
3 Reserved For future use by ITU-T | ISO/IEC
4 primary x y Rec. ITU-R BT.470-6 System M (historical)
green 0.21 0.71
United States National Television System
Committee 1953 Recommendation for
blue 0.14 0.08
transmission standards for colour television
red 0.67 0.33
United States Federal Communications
white C 0.310 0.316
Commission Title 47 Code of Federal Regulations
(2003) 73.682 (a) (20)
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ISO/IEC 23091-2:2021(E)
Table 3 (continued)
Value Colour primaries Informative remarks
5 primary x y Rec. ITU-R BT.470-6 System B, G (historical)
green 0.29 0.60
Rec. ITU-R BT.601-7 625
blue 0.15 0.06
Rec. ITU-R BT.1358-0 625 (historical)
red 0.64 0.33
Rec. ITU-R BT.1700-0 625 PAL and 625 SECAM
white D65 0.3127 0.3290
6 primary x y Rec. ITU-R BT.601-7 525
green 0.310 0.595
Rec. ITU-R BT.1358-1 525 or 625 (historical)
blue 0.155 0.070
Rec. ITU-R BT.1700-0 NTSC
red 0.630 0.340
Society of Motion Picture and Television
white D65 0.3127 0.3290 Engineers ST 170 (2004)
(functionally the same as the value 7)
7 primary x y Society of Motion Picture and Television
Engineers ST 240 (1999)
green 0.310 0.595
(functionally the same as the value 6)
blue 0.155 0.070
red 0.630 0.340
white D65 0.3127 0.3290
8 primary x y Generic film (colour filters using Illuminant C)
green 0.243 0.692 (Wratten 58)
blue 0.145 0.049 (Wratten 47)
red 0.681 0.319 (Wratten 25)
white C 0.310 0.316
9 primary x y Rec. ITU-R BT.2020-2
green 0.170 0.797
Rec. ITU-R BT.2100-2
blue 0.131 0.046
red 0.708 0.292
white D65 0.3127 0.3290
10 primary x y Society of Motion Picture and Television
Engineers ST 428-1 (2019)
green (Y) 0.0 1.0
(CIE 1931 XYZ as in ISO/CIE 11664-1)
blue (Z) 0.0 0.0
red (X) 1.0 0.0
centre white 1 ÷ 3 1 ÷ 3
11 primary x y Society of Motion Picture and Television
Engineers RP 431-2 (2011)
green 0.265 0.690
blue 0.150 0.060
red 0.680 0.320
white 0.314 0.351
12 primary x y Society of Motion Picture and Television
Engineers EG 432-1 (2010)
...
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