ISO/IEC TR 23008-15:2018

Information technology — High efficiency coding and media delivery in heterogeneous environments — Part 15: Signalling, backward compatibility and display adaptation for HDR/WCG video

This document reviews approaches for processing and coding of HDR/WCG video content. The purpose of this document is to provide a set of publicly-referenceable methods for the operation of AVC or HEVC video coding systems adapted for compressing HDR/WCG video for consumer distribution applications. This document first includes a review of the video usability information (VUI) indicators and supplemental enhancement information (SEI) messages applicable for HDR/WCG video. It provides a description of processing steps for converting from 4:4:4 RGB linear light representation video signals into video signals with ICTCP colour representation and perceptual quantizer (PQ) transfer function, or with Y′CbCr colour representation and HLG transfer function (ICTCP, PQ and HLG are defined in Rec. ITU-R BT.2100-1). Some high-level approaches for compressing these signals using either Rec. ITU-T H.264 | ISO/IEC 14496-10 or Rec. ITU-T H.265 | ISO/IEC 23008-2 are provided. A description of post-decoding processing steps is also included for converting back to a linear light, 4:4:4 RGB representation. The document also addresses the standard dynamic range (SDR) backward compatibility, that is, the compatibility with legacy decoding systems that are not able to detect and properly display HDR/WCG video content. It describes example implementations of this feature using three different solutions: using HLG as a backward compatible transfer function, using CRI and TMI SEI messages, using dual-layer approach with the Scalable Main 10 profile of HEVC and an SDR compatible base layer. Finally, the document illustrates the usage of CRI SEI messages to convey metadata enabling the dynamic range and colour gamut adaptation at the display side of the decoded video to the display capabilities. NOTE The document complements the material provided in ITU-T H.Sup15 | ISO/IEC TR 23008-14, which is focused on conversion and coding practices for non-constant luminance (NCL) Y′CbCr video signals using the PQ transfer function.

Technologies de l'information — Codage à haut rendement et fourniture de supports dans les environnements hétérogènes — Partie 15: Signalisation, compatibilité amont et adaptation de l'affichage pour la vidéo HDR/WCG

General Information

• Status: Published
• Publication Date: 06-Aug-2018
• ICS: 35.040.40 - Coding of audio, video, multimedia and hypermedia information
• Technical Committee: ISO/IEC JTC 1/SC 29 - Coding of audio, picture, multimedia and hypermedia information
• Drafting Committee: ISO/IEC JTC 1/SC 29 - Coding of audio, picture, multimedia and hypermedia information
• Current Stage: 6060 - International Standard published
• Due Date: 21-Oct-2019
• Completion Date: 07-Aug-2018

Standards Content (Sample)

TECHNICAL ISO/IEC TR
REPORT 23008-15
First edition
2018-08
Information technology — High
efficiency coding and media delivery
in heterogeneous environments —
Part 15:
Signalling, backward compatibility and
display adaptation for HDR/WCG video
Technologies de l'information — Codage à haut rendement et
fourniture de supports dans les environnements hétérogènes —
Partie 15: Signalisation, compatibilité amont et adaptation de
l'affichage pour la vidéo HDR/WCG
Reference number
ISO/IEC TR 23008-15:2018(E)
©
ISO/IEC 2018

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ISO/IEC TR 23008-15:2018(E)

COPYRIGHT PROTECTED DOCUMENT
© ISO/IEC 2018
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
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Email: [e-mail]
Website: www.iso.org
Published in Switzerland
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ISO/IEC TR 23008-15:2018(E)

Contents Page
Foreword .v
Introduction .vi
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Abbreviated terms . 3
5 Conventions . 4
5.1 General . 4
5.2 Arithmetic operators . 5
5.3 Bit-wise operators. 5
5.4 Assignment operators . 6
5.5 Relational, logical and other operators . 6
5.6 Mathematical functions . 6
5.7 Order of operations . 7
6 Overview . 8
7 HEVC signalling mechanisms applicable to HDR/WCG video . 9
7.1 General . 9
7.2 VUI syntax elements . 9
7.3 SEI messages applicable for HDR/WCG video .10
7.3.1 General.10
7.3.2 Mastering display colour volume SEI message . .10
7.3.3 Content light level information SEI message .11
7.3.4 Ambient viewing environment SEI message .11
7.3.5 Alternative transfer characteristics SEI message .11
7.3.6 Tone mapping information SEI message .11
7.3.7 Colour remapping information SEI message .12
7.4 Overview of PQ and HLG transfer functions .13
7.4.1 General.13
7.4.2 Reference PQ EOTF .14
7.4.3 Reference HLG OETF .15
7.5 IC C colour representation .16
T P
7.5.1 General.16
7.5.2 Pre-encoding process .17
7.5.3 Encoding process . .20
7.5.4 Decoding process .22
7.5.5 Post-decoding process .22
8 Bitstream SDR backward compatibility with single-layer coding .24
8.1 General .24
8.2 Approach 1: usage of HLG for “static” bitstream SDR backward compatibility .24
8.2.1 General.24
8.2.2 HLG pre-encoding conversion process .25
8.2.3 Encoding process . .27
8.2.4 Decoding process .29
8.2.5 HLG post-decoding conversion .29
8.2.6 Colour representation conversion: Y′CbCr to R′G′B′ .30
8.3 Approach 2: usage of SEI messages for “dynamic” bitstream SDR backward
compatibility .30
8.3.1 General.30
8.3.2 CRI applied in Y′CbCr 4:2:0 domain .31
8.3.3 CRI applied in Y′CbCr 4:4:4 domain .32
8.3.4 TMI applied in R′G′B′ 4:4:4 domain .33
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ISO/IEC TR 23008-15:2018(E)

8.3.5 Derivation of DRA functions .34
8.3.6 Settings with colour remapping information SEI message .35
8.3.7 Settings with tone mapping information SEI message .36
9 Bitstream SDR backward compatibility with dual-layer SHVC coding .37
9.1 General .37
9.2 Encoding and decoding stages .37
10 Display adaptation.39
10.1 General .39
10.2 Display SDR backward compatibility .39
10.2.1 Conversion and coding process example .39
10.2.2 Using colour remapping information SEI message .41
Bibliography .43
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ISO/IEC TR 23008-15:2018(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. In the field of information technology, ISO and IEC have established a joint technical committee,
ISO/IEC JTC 1.
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).
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
For an explanation on 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 the following
URL: www .iso .org/iso/foreword .html.
This document was prepared by Technical Committee ISO/IEC JTC 1, Information technology,
Subcommittee SC 29, Coding of audio, picture, multimedia and hypermedia information, in collaboration
with ITU-T. A technically aligned twin text is published as ITU-T H.Sup18.
A list of all parts in the ISO/IEC 23008 series can be found on the ISO website.
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ISO/IEC TR 23008-15:2018(E)

Introduction
High dynamic range (HDR) video is a type of video content in which the sample values represent a
larger luminance range than conventional standard dynamic range (SDR) video. HDR video can provide
an enhanced viewer experience and can more accurately reproduce scenes that include, within the
same image, dark areas and bright highlights, such as emissive light sources and reflections. Wide
colour gamut (WCG) video, on the other hand, is video characterized by a wider spectrum of colours
compared to what has been commonly available in conventional video. Recent advances in capture and
display technology have enabled consumer distribution of HDR and WCG content. However, given the
characteristics of such content, special considerations may need to be made, in terms of both processing
and compression, compared to conventional content.
This document relates to HDR/WCG video coding and distribution, using single-layer or dual-layer
coding, with the signalling specified for Rec. ITU-T H.265 | ISO/IEC 23008-2 High efficiency video coding
(HEVC), and when applicable, Rec. ITU-T H.264 | ISO/IEC 14496-10 Advanced video coding (AVC).
This document serves several purposes:
— It provides a survey of identified video usability information (VUI) syntax elements and supplemental
enhancement information (SEI) messages specified in HEVC and AVC applicable for HDR/WCG video.
— It covers conversion and coding chains using the IC C colour representation, and the hybrid log-
T P
gamma (HLG) transfer functions.
— Examples of using colour remapping information (CRI) and tone mapping information (TMI) SEI
messages for the support of SDR backward compatibility and display adaptation functionalities are
described.
— A dual-layer coding approach using the Scalable Main 10 profile of HEVC for backward compatibility
with SDR systems is also documented.
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TECHNICAL REPORT ISO/IEC TR 23008-15:2018(E)
Information technology — High efficiency coding and
media delivery in heterogeneous environments —
Part 15:
Signalling, backward compatibility and display adaptation
for HDR/WCG video
1 Scope
This document reviews approaches for processing and coding of HDR/WCG video content. The purpose
of this document is to provide a set of publicly-referenceable methods for the operation of AVC or HEVC
video coding systems adapted for compressing HDR/WCG video for consumer distribution applications.
This document first includes a review of the video usability information (VUI) indicators and
supplemental enhancement information (SEI) messages applicable for HDR/WCG video. It provides a
description of processing steps for converting from 4:4:4 RGB linear light representation video signals
into video signals with IC C colour representation and perceptual quantizer (PQ) transfer function,
T P
or with Y′CbCr colour representation and HLG transfer function (IC C , PQ and HLG are defined in Rec.
T P
ITU-R BT.2100-1). Some high-level approaches for compressing these signals using either Rec. ITU-T
H.264 | ISO/IEC 14496-10 or Rec. ITU-T H.265 | ISO/IEC 23008-2 are provided. A description of post-
decoding processing steps is also included for converting back to a linear light, 4:4:4 RGB representation.
The document also addresses the standard dynamic range (SDR) backward compatibility, that is, the
compatibility with legacy decoding systems that are not able to detect and properly display HDR/WCG
video content. It describes example implementations of this feature using three different solutions:
using HLG as a backward compatible transfer function, using CRI and TMI SEI messages, using dual-
layer approach with the Scalable Main 10 profile of HEVC and an SDR compatible base layer. Finally, the
document illustrates the usage of CRI SEI messages to convey metadata enabling the dynamic range
and colour gamut adaptation at the display side of the decoded video to the display capabilities.
NOTE The document complements the material provided in ITU-T H.Sup15 | ISO/IEC TR 23008-14, which is
focused on conversion and coding practices for non-constant luminance (NCL) Y′CbCr video signals using the PQ
transfer function.
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.
Recommendation ITU-T H.264 | ISO/IEC 14496-10: 2014, Information technology — Coding of audio-
visual objects — Part 10: Advanced Video Coding
Recommendation ITU-T H.265 | ISO/IEC 23008-2: 2017, Information technology — High efficiency coding
and media delivery in heterogeneous environments — Part 2: High efficiency video coding
3 Terms and definitions
For the purposes of this document, the terms and definitions given in Rec. ITU-T H.264 | ISO/IEC 14496-
10, Rec. ITU-T H.265 | ISO/IEC 23008-2, and the following apply.
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ISO/IEC TR 23008-15:2018(E)

ISO and IEC maintain terminological databases for use in standardization at the following addresses:
— IEC Electropedia: available at http: //www .electropedia .org/
— ISO Online browsing platform: available at https: //www .iso .org/obp
3.1
dynamic range adaptation
DRA
mapping process to convert content from one colour volume to another colour volume
3.2
electro-optical transfer function
EOTF
function which converts a non-linear video signal into a quantity of output linear light
Note 1 to entry: An example of output linear light is light emitted by a display.
3.3
full range
range in a fixed-point (integer) representation that spans the full range of values that could be
expressed with that bit depth, such that, for 10-bit signals, black corresponds to code value 0 and peak
white corresponds to code value 1023 for Y′
Note 1 to entry: As per the full range definition from Rec. ITU-R BT.2100-1.
3.4
hybrid log-gamma
HLG
one set of transfer functions offering a degree of compatibility with legacy displays by more closely
matching the previously established television transfer curves
Note 1 to entry: Sets of transfer functions related to HDR signals are specified in Rec. ITU-R BT.2100-1.
3.5
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 such that, for 10-bit representations, the range from 64 (black) to 940
(peak white) is used for Y′ and the range from 64 to 960 is used for Cb and Cr
Note 1 to entry: As per the narrow range definition from Rec. ITU-R BT.2100-1.
3.6
opto-electronic transfer function
OETF
function which converts a source input linear optical intensity into a non-linear video signal
Note 1 to entry: An example of input linear optical intensity is light input to a camera.
3.7
opto-optical transfer function
OOTF
function which has the role of applying the “rendering intent” on video signal
Note 1 to entry: In general, an OOTF is a concatenation of an OETF, artistic adjustments and an EOTF.
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3.8
perceptual quantizer
PQ
one set of transfer functions achieving a very wide range of brightness levels for a given bit depth using
a non-linear transfer function that is finely tuned to match the human visual system
Note 1 to entry: Sets of transfer functions related to HDR signals are specified in Rec. ITU-R BT.2100-1.
3.9
random access point access unit
RAPAU
access unit in the bitstream at which the initiation of the decoding process for some or all subsequent
pictures in the bitstream is intended to be feasible
3.10
reference electro-optical transfer function
reference EOTF
specified EOTF for use under specific viewing environment, named the reference viewing environment
3.11
reference opto-electronic transfer function
reference OETF
specified OETF implemented within cameras, to ensure consistency of the image between cameras
from different manufacturers
3.12
reference viewing environment
parameters to establish a reproducible viewing environment for critical viewing of material that can
provide repeatable results from one facility to another when viewing the same material
Note 1 to entry: Rec. ITU-R BT.2100-1:2017, Table 3 provides reference viewing environment parameters for HDR
programme material.
4 Abbreviated terms
For the purposes of this document, the abbreviated terms given in Rec. ITU-T H.264 | ISO/IEC 14496-10,
Rec. ITU-T H.265 | ISO/IEC 23008-2 and the following apply.
ATC alternative transfer characteristics
AVC advanced video coding, specified in Rec. ITU-T H.264 | ISO/IEC 14496-10
AVE ambient viewing environment
CGS colour gamut scalability
CI constant intensity
CL constant luminance
CLL content light level
CLVS coded layer-wise video sequence
CRI colour remapping information
FIR finite impulse response
HDR high dynamic range
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ISO/IEC TR 23008-15:2018(E)

HEVC high efficiency video coding, specified in Rec. ITU-T H.265 | ISO/IEC 23008-2
IC C alternative colour space representation to Y′CbCr, specified in Rec. ITU-R BT.2100-1
T P
LMS long, medium, and short wavelength-based colour space, specified in Rec. ITU-R BT.2100-1
LUT look-up table
MAD mean absolute difference
MDCV mastering display colour volume
NCL non-constant luminance
PQ10 HDR content representation that utilizes the Rec. ITU-R BT.2100-1 colour primaries, the Rec.
ITU-R BT.2100-1 reference PQ EOTF, and the Rec. ITU-R BT.2100-1 Y′CbCr colour space rep-
resentation with 10 bits per sample in the 4:2:0 chroma sampling format
QP quantization parameter
RGB colour system using red, green, and blue components
SDR standard dynamic range
SEI supplemental enhancement information
SHVC scalable high efficiency video coding
SPS sequence parameter set
SSE sum of squared errors
TMI tone mapping information
UHD ultra-high definition
VUI video usability information
WCG wide colour gamut
XYZ CIE 1931 colour space; Y corresponds to the luminance signal
Y′CbCr colour space representation commonly used for video/image distribution as a way of encod-
ing RGB information, also commonly expressed as YCbCr, Y′C C , or Y′C′ C′
B R B R
[The relationship between Y′CbCr and RGB is dictated by certain signal parameters, such
as colour primaries, transfer characteristics, and matrix coefficients. Unlike the (constant
luminance) Y component in the XYZ representation, Y′ in this representation might not be
representing the same quantity. Y′ is commonly referred to as “luma”. Cb and Cr are com-
monly referred to as “chroma”.]
5 Conventions
5.1 General
The mathematical operators used in this document are similar to those used in the C programming
language. However, the results of integer division and arithmetic shift operations are defined more
precisely, and additional operations are defined, such as exponentiation and real-valued division.
Numbering and counting conventions generally begin from 0, e.g., “the first” is equivalent to the 0-th,
“the second” is equivalent to the 1-th, etc.
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5.2 Arithmetic operators
+ addition
− subtraction (as a two-argument operator) or negation (as a unary prefix operator)
* multiplication, including matrix multiplication
exponentiation
y
(Denotes x to the power of y. In other contexts, such notation is used for superscripting not
x
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.]
÷ 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
fi summation of f( i ) with i taking all integer values from x up to and including y
()
∑
i=x
modulus
x % y
(Remainder of x divided by y, defined only for integers x and y with x >= 0 and y > 0.)
5.3 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 anoth-
er 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 anoth-
er 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 anoth-
er 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 (This function is 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
x << y (This function is defined 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.)
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ISO/IEC TR 23008-15:2018(E)

5.4 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)
5.5 Relational, logical and other operators
== equality operator
!= not equal to operator
!x logical negation “not”
> larger than
...