ISO/IEC 23090-3:2021

INTERNATIONAL ISO/IEC
STANDARD 23090-3
First edition
2021-02
Information technology — Coded
representation of immersive media —
Part 3:
Versatile video coding
Technologies de l'information — Représentation codée de média
immersifs —
Partie 3: Codage vidéo polyvalent
Reference number
©
ISO/IEC 2021
© ISO/IEC 2021
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ii © ISO/IEC 2021 – All rights reserved

Contents
Foreword . vi
Introduction . vii
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Abbreviated terms . 13
5 Conventions. 16
5.1 General . 16
5.2 Arithmetic operators . 16
5.3 Logical operators . 16
5.4 Relational operators . 17
5.5 Bit-wise operators . 17
5.6 Assignment operators . 17
5.7 Range notation . 17
5.8 Mathematical functions . 17
5.9 Order of operation precedence. 18
5.10 Variables, syntax elements and tables . 19
5.11 Text description of logical operations . 20
5.12 Processes . 21
6 Bitstream and picture formats, partitionings, scanning processes and neighbouring relationships . 21
6.1 Bitstream formats . 21
6.2 Source, decoded and output picture formats . 21
6.3 Partitioning of pictures, subpictures, slices, tiles, and CTUs . 23
6.3.1 Partitioning of pictures into subpictures, slices, and tiles . 23
6.3.2 Block, quadtree and multi-type tree structures . 25
6.3.3 Spatial or component-wise partitionings . 26
6.4 Availability processes . 27
6.4.1 Allowed quad split process . 27
6.4.2 Allowed binary split process . 27
6.4.3 Allowed ternary split process . 29
6.4.4 Derivation process for neighbouring block availability . 30
6.5 Scanning processes . 30
6.5.1 CTB raster scanning, tile scanning, and subpicture scanning processes . 30
6.5.2 Up-right diagonal scan order array initialization process . 34
6.5.3 Horizontal and vertical traverse scan order array initialization process . 35
7 Syntax and semantics . 35
7.1 Method of specifying syntax in tabular form . 35
7.2 Specification of syntax functions and descriptors . 36
7.3 Syntax in tabular form . 38
7.3.1 NAL unit syntax . 38
7.3.2 Raw byte sequence payloads, trailing bits and byte alignment syntax . 38
7.3.3 Profile, tier, and level syntax . 57
7.3.4 DPB parameters syntax . 60
7.3.5 Timing and HRD parameters syntax . 60
7.3.6 Supplemental enhancement information message syntax . 61
7.3.7 Slice header syntax . 62
7.3.8 Weighted prediction parameters syntax . 64
7.3.9 Reference picture lists syntax . 65
7.3.10 Reference picture list structure syntax . 66
7.3.11 Slice data syntax . 66
7.4 Semantics . 88
7.4.1 General . 88
7.4.2 NAL unit semantics . 88
© ISO/IEC 2021 – All rights reserved  iii

7.4.3 Raw byte sequence payloads, trailing bits and byte alignment semantics . 95
7.4.4 Profile, tier, and level semantics . 141
7.4.5 DPB parameters semantics . 146
7.4.6 Timing and HRD parameters semantics . 146
7.4.7 Supplemental enhancement information message semantics . 150
7.4.8 Slice header semantics . 150
7.4.9 Weighted prediction parameters semantics . 158
7.4.10 Reference picture lists semantics . 159
7.4.11 Reference picture list structure semantics . 160
7.4.12 Slice data semantics . 161
8 Decoding process . 183
8.1 General decoding process . 183
8.1.1 General . 183
8.1.2 Decoding process for a coded picture . 184
8.2 NAL unit decoding process . 185
8.3 Slice decoding process. 185
8.3.1 Decoding process for picture order count . 185
8.3.2 Decoding process for reference picture lists construction . 187
8.3.3 Decoding process for reference picture marking . 191
8.3.4 Decoding process for generating unavailable reference pictures . 192
8.3.5 Decoding process for symmetric motion vector difference reference indices . 192
8.3.6 Decoding process for collocated picture and no backward prediction . 193
8.4 Decoding process for coding units coded in intra prediction mode . 194
8.4.1 General decoding process for coding units coded in intra prediction mode . 194
8.4.2 Derivation process for luma intra prediction mode . 195
8.4.3 Derivation process for chroma intra prediction mode . 198
8.4.4 Cross-component chroma intra prediction mode checking process . 199
8.4.5 Decoding process for intra blocks . 200
8.5 Decoding process for coding units coded in inter prediction mode . 231
8.5.1 General decoding process for coding units coded in inter prediction mode . 231
8.5.2 Derivation process for motion vector components and reference indices . 235
8.5.3 Decoder-side motion vector refinement process . 254
8.5.4 Derivation process for geometric partitioning mode motion vector components and reference

indices . 259
8.5.5 Derivation process for subblock motion vector components and reference indices . 260
8.5.6 Decoding process for inter blocks . 285
8.5.7 Decoding process for geometric partitioning mode inter blocks . 307
8.5.8 Decoding process for the residual signal of coding blocks coded in inter prediction mode . 313
8.5.9 Decoding process for the reconstructed signal of chroma coding blocks coded in inter

prediction mode . 314
8.6 Decoding process for coding units coded in IBC prediction mode . 316
8.6.1 General decoding process for coding units coded in IBC prediction mode . 316
8.6.2 Derivation process for block vector components for IBC blocks . 317
8.6.3 Decoding process for IBC blocks . 321
8.7 Scaling, transformation and array construction process . 322
8.7.1 Derivation process for quantization parameters . 322
8.7.2 Scaling and transformation process . 324
8.7.3 Scaling process for transform coefficients. 325
8.7.4 Transformation process for scaled transform coefficients . 327
8.7.5 Picture reconstruction process . 347
8.8 In-loop filter process . 350
8.8.1 General . 350
8.8.2 Picture inverse mapping process for luma samples . 350
8.8.3 Deblocking filter process . 351
8.8.4 Sample adaptive offset process . 377
8.8.5 Adaptive loop filter process . 379
9 Parsing process . 391
9.1 General . 391
9.2 Parsing process for k-th order Exp-Golomb codes . 391
9.2.1 General . 391
9.2.2 Mapping process for signed Exp-Golomb codes . 392
iv  © ISO/IEC 2021 – All rights reserved

9.3 CABAC parsing process for slice data . 393
9.3.1 General . 393
9.3.2 Initialization process . 394
9.3.3 Binarization process . 418
9.3.4 Decoding process flow . 427
Annex A (normative) Profiles, tiers and levels. 444
Annex B (normative) Byte stream format . 456
Annex C (normative) Hypothetical reference decoder . 458
Annex D (normative) Supplemental enhancement information and use of SEI and VUI . 480
Bibliography . 504

© ISO/IEC 2021 – All rights reserved  v

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 Joint Technical Committee 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 H.266 (08/2020).
A list of all parts in the ISO/IEC 23090 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.

vi  © ISO/IEC 2021 – All rights reserved

SO/IEC VVC
Introduction
Purpose
This document specifies a video coding technology known as versatile video coding. It has been designed with two primary
goals. The first of these is to specify a video coding technology with a compression capability that is substantially beyond
that of the prior generations of such standards, and the second is for this technology to be highly versatile for effective use
in a broader range of applications than that addressed by prior standards. Some key application areas for the use of this
document particularly include ultra-high-definition video (e.g., with 3840×2160 or 7620×4320 picture resolution and bit
depth of 10 bits as specified in Rec. ITU-R BT.2100), video with a high dynamic range and wide colour gamut (e.g., with
the perceptual quantization or hybrid log-gamma transfer characteristics specified in Rec. ITU-R BT.2100), and video for
immersive media applications such as 360° omnidirectional video projected using a common projection format such as the
equirectangular or cubemap projection formats, in addition to the applications that have commonly been addressed by prior
video coding standards.
Profiles, tiers, and levels
This document is designed to be versatile in the sense that it serves a wide range of applications, bit rates, resolutions,
qualities, and services. Applications include, but are not limited to, video coding for digital storage media, television
broadcasting, video streaming services, real-time communication. In the course of creating this document, various
requirements from typical applications have been considered, necessary algorithmic elements have been developed, and
these have been integrated into a single syntax. Hence, this document is designed to facilitate video data interchange among
different applications.
Considering the practicality of implementing the full syntax of this document, however, a limited number of subsets of the
syntax are also stipulated by means of "profiles", "tiers", and "levels". These and other related terms are formally defined
in Clause 3.
A "profile" is a subset of the entire bitstream syntax that is specified in this document. Within the bounds imposed by the
syntax of a given profile it is still possible to require a very large variation in the performance of encoders and decoders
depending upon the values taken by syntax elements in the bitstream, such as the specified size of the decoded pictures. In
many applications, it is currently neither practical nor economical to implement a decoder capable of dealing with all
hypothetical uses of the syntax within a particular profile.
In order to deal with this problem, "tiers" and "levels" are specified within each profile. A level of a tier is a specified set
of constraints imposed on values of the syntax elements in the bitstream. Some of these constraints are expressed as simple
limits on values, while others take the form of constraints on arithmetic combinations of values (e.g. picture width
multiplied by picture height multiplied by number of pictures decoded per second). A level specified for a lower tier is
more constrained than a level specified for a higher tier.
Coded video content conforming to this document uses a common syntax. In order to achieve a subset of the complete
syntax, flags, parameters, and other syntax elements are included in the bitstream that signal the presence or absence of
syntactic elements that occur later in the bitstream.
Encoding process, decoding process, and use of VUI parameters and SEI messages
Any encoding process that produces bitstream data that conforms to the specified bitstream syntax format requirements of
this document is considered to be in conformance with the requirements of this document. The decoding process is
specified such that all decoders that conform to a specified combination of capabilities known as the profile, tier, and level
will produce numerically identical cropped decoded output pictures when invoking the decoding process associated with
that profile for a bitstream conforming to that profile, tier and level. Any decoding process that produces identical cropped
decoded output pictures to those produced by the process described herein (with the correct output order or output timing,
as specified) is considered to be in conformance with the requirements of this document.
Rec. ITU-T H.274 | ISO/IEC 23002-7 specifies the syntax and semantics of the video usability information (VUI)
parameters and supplemental enhancement information (SEI) messages that do not affect the conformance specifications
in Annex C. These VUI parameters and SEI messages may be used together with this document.
Versions of this document
This is the first edition of this document.
© ISO/IEC 2021 – All rights reserved vii

Overview of the design characteristics
The coded representation specified in the syntax is designed to enable a high compression capability for a desired image
or video quality. The algorithm is typically not mathematically lossless, as the exact source sample values are typically not
preserved through the encoding and decoding processes, although some modes are included that provide lossless coding
capability. A number of techniques are specified to enable highly efficient compression. Encoding algorithms (not
specified within the scope of this document) may select between inter, intra, intra block copy (IBC), and palette coding for
block-shaped regions of each picture. Inter coding uses motion vectors for block-based inter-picture prediction to exploit
temporal statistical dependencies between different pictures, intra coding uses various spatial prediction modes to exploit
spatial statistical dependencies in the source signal within the same picture, and intra block copy coding uses block
displacement vectors to reference previously decoded regions of the same picture to exploit statistical similarities among
different areas of the same picture. Motion vectors, intra prediction modes, and IBC block vectors are specified for a
variety of block sizes in the picture. The prediction residual can then be further compressed using a spatial transform to
remove spatial correlation inside a block before it is quantized, producing a possibly irreversible process that typically
discards less important visual information while forming a close approximation to the source samples. Finally, the motion
vectors, intra prediction modes, and block vectors can also be further compressed using a variety of prediction mechanisms,
and, after prediction, are combined with the quantized transform coefficient information and encoded using arithmetic
coding.
How to read this document
It is suggested that the reader starts with Clause 1 and moves on to Clause 3. Clause 6 should be read for the geometrical
relationship of the source, input, and output of the decoder. Clause 7 specifies the order to parse syntax elements from the
bitstream. See subclauses 7.1 to 7.3 for syntactical order and subclause 7.4 for semantics; e.g. the scope, restrictions, and
conditions that are imposed on the syntax elements. The actual parsing for most syntax elements is specified in Clause 9.
Finally, Clause 8 specifies how the syntax elements are mapped into decoded samples. Throughout reading this document,
the reader should refer to Clauses 2, 4, and 5 as needed. Annexes A through D also form an integral part of this document.
Annex A specifies profiles, each being tailored to certain application domains, and defines the so-called tiers and levels of
the profiles. Annex B specifies syntax and semantics of a byte stream format for delivery of coded video as an ordered
stream of bytes. Annex C specifies the hypothetical reference decoder, bitstream conformance, decoder conformance, and
the use of the hypothetical reference decoder to check bitstream and decoder conformance. Annex D specifies syntax and
semantics for supplemental enhancement information (SEI) message payloads that affect the conformance specifications
in Annex C. Rec. ITU-T H.274 | ISO/IEC 23002-7 specifies the syntax and semantics of the video usability information
(VUI) parameters as well as SEI messages that do not affect the conformance specifications in Annex C. These VUI
parameters and SEI messages may be used together with this document.
Patent declarations
The International Organization for Standardization (ISO) and International Electrotechnical Commission (IEC) draw
attention to the fact that it is claimed that compliance with this document may involve the use of patents.
ISO and IEC take no position concerning the evidence, validity and scope of these patent rights.
The holders of these patent rights have assured ISO and IEC that they are willing to negotiate licences under reasonable
and non-discriminatory terms and conditions with applicants throughout the world. In this respect, the statements of the
holders of these patent rights are registered with ISO and IEC. Information may be obtained from the patent database
available at www.iso.org/patents.
Attention is drawn to the possibility that some of the elements of this document may be the subject of patent rights other
than those in the patent database. ISO and IEC shall not be held responsible for identifying any or all such patent rights.
viii  © ISO/IEC 2021 – All rights reserved

INTERNATIONAL STANDARD ISO/IEC 23090-3:2021(E)

Information technology — Coded representation of immersive media —
Part 3: Versatile video coding
1 Scope
This document specifies a video coding technology known as versatile video coding (VVC), comprising a video coding
technology with a compression capability that is substantially beyond that of the prior generations of such standards and
with sufficient versatility for effective use in a broad range of applications.
Only the syntax format, semantics, and associated decoding process requirements are specified, while other matters such
as pre-processing, the encoding process, system signalling and multiplexing, data loss recovery, post-processing, and video
display are considered to be outside the scope of this document. Additionally, the internal processing steps performed
within a decoder are also considered to be outside the scope of this document; only the externally observable output
behaviour is required to conform to the specifications of this document.
This document is designed to be generic in the sense that it serves a wide range of applications, bit rates, resolutions,
qualities and services. Applications include, but are not limited to, video coding for digital storage media, television
broadcasting and real-time communication. In the course of creating This document, various requirements from typical
applications have been considered, necessary algorithmic elements have been developed, and these have been integrated
into a single syntax. Hence, this document is designed to facilitate video data interchange among different applications.
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.274 | ISO/IEC 23002-7, Versatile supplemental enhancement information messages for coded video
bitstreams
Rec. ITU-T T.35:2000, Procedure for the allocation of ITU-T defined codes for non standard facilities.
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
access unit
set of PUs that belong to different layers and contain coded pictures associated with the same time for output from the
DPB
3.2
adaptive colour transform
cross-component transform applied to the decoded residual of a coding unit in the 4:4:4 colour format prior to
reconstruction and loop filtering
3.3
adaptive loop filter
filtering process that is applied as part of the decoding process and is controlled by parameters conveyed in an APS
3.4
AC transform coefficient
transform coefficient for which the frequency index in at least one of the two dimensions is non-zero
3.5
ALF APS
APS that controls the ALF process
© ISO/IEC 2021 – All rights reserved  1

3.6
adaptation parameter set
syntax structure containing syntax elements that apply to zero or more slices as determined by zero or more syntax
elements found in slice headers
3.7
associated GDR picture
previous GDR picture (when present) in decoding order, for a particular picture with nuh_layer_id equal to a particular
value layerId, that has nuh_layer_id equal to layerId and between which and the particular picture in decoding order
there is no IRAP picture with nuh_layer_id equal to layerId
3.8
associated GDR subpicture
previous GDR subpicture (when present) in decoding order, for a particular subpicture with nuh_layer_id equal to a
particular value layerId and subpicture index equal to a particular value subpicIdx, that has nuh_layer_id equal to layerId
and subpicture index equal to subpicIdx and between which and the particular subpicture in decoding order there is no
IRAP subpicture with nuh_layer_id equal to layerId and subpicture index equal to subpicIdx
3.9
associated IRAP picture
previous IRAP picture (when present) in decoding order, for a particular picture with nuh_layer_id equal to a particular
value layerId, that has nuh_layer_id equal to layerId and between which and the particular picture in decoding order
there is no GDR picture with nuh_layer_id equal to layerId
3.10
associated IRAP subpicture
previous IRAP subpicture (when present) in decoding order, for a particular subpicture with nuh_layer_id equal to a
particular value layerId and subpicture index equal to a particular value subpicIdx, that has nuh_layer_id equal to layerId
and subpicture index equal to subpicIdx and between which and the particular subpicture in decoding order there is no
GDR subpicture with nuh_layer_id equal to layerId and subpicture index equal to subpicIdx
3.11
associated non-VCL NAL unit
non-VCL NAL unit (when present) for a VCL NAL unit where the VCL NAL unit is the associated VCL NAL unit of the
non-VCL NAL unit
3.12
associated VCL NAL unit
preceding VCL NAL unit in decoding order for a non-VCL NAL unit with nal_unit_type equal to EOS_NUT, EOB_NUT,
SUFFIX_APS_NUT, SUFFIX_SEI_NUT, FD_NUT, RSV_NVCL_27, UNSPEC_30, or UNSPEC_31; or otherwise the
next VCL NAL unit in decoding order
3.13
bin
bit of a bin string
3.14
binarization
set of bin strings for all possible values of a syntax element
3.15
binarization process
unique mapping process of all possible values of a syntax element onto a set of bin strings
3.16
binary split
split of a rectangular MxN block of samples into two blocks where a vertical split results in a first (M / 2)xN block and a
second (M / 2)xN block, and a horizontal split results in a first Mx(N / 2) block and a second Mx(N / 2) block
3.17
bin string
intermediate binary representation of values of syntax elements from the binarization of the syntax element
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3.18
bi-predictive slice
B slice
slice that is decoded using intra prediction or using inter prediction with at most two motion vectors and reference
indices to predict the sample values of each block
3.19
bitstream
sequence of bits, in the form of a NAL unit stream or a byte stream, that forms the representation of a sequence of AUs
forming one or more coded video sequences (CVSs)
3.20
block
MxN (M-column by N-row) array of samples, or an MxN array of transform coefficients
3.21
block vector
two-dimensional vector that provides an offset from the coordinates of the current coding block to the coordinates of the
reference block in the same decoded slice
3.22
byte
sequence of 8 bits, within which, when written or read as a sequence of bit values, the left-most and right-most bits
represent the most and least significant bits, respectively
3.23
byte-aligned
positioned an integer multiple of 8 bits from the position of the first bit in the bitstream
3.24
byte-aligned
position at which it appears in a bitstream is byte-aligned
3.25
byte stream
encapsulation of a NAL unit stream into a series of bytes containing start code prefixes and NAL units
3.26
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 the term chrominance in order to avoid the implication of the use of linear light
transfer characteristics that is often associated with the term chrominance.
3.27
CRA PU
PU in which the coded picture is a CRA picture
3.28
CRA picture
IRAP picture for which each VCL NAL unit has nal_unit_type equal to CRA_NUT
Note 1 to entry: A CRA picture does not use inter prediction in its decoding process, and could be the first picture in the bitstream in
decoding order, or could appear later in the bitstream. A CRA picture could have associated RADL or RASL pictures. When a CRA
picture has NoOutputBeforeRecoveryFlag equal to 1, the associated RASL pictures are not output by the decoder, because they might
not be decodable, as they could contain references to pictures that are not present in the bitstream.
3.29
CRA subpicture
IRAP subpicture for which each VCL NAL unit has nal_unit_type equal to CRA_NUT
3.30
coded layer video sequence:
sequence of PUs with the same value of nuh_layer_id that consists, in decoding order, of a CLVSS PU, followed by zero
or more PUs that are not CLVSS PUs, including all subsequent PUs up to but not including any subsequent PU that is a
CLVSS PU
Note 1 to entry: A CLVSS PU could be an IDR PU, a CRA PU, or a GDR PU. The value of NoOutputBeforeRecoveryFlag is equal to
1 for each IDR PU, and each CRA PU that has HandleCraAsClvsStartFlag equal to 1, and each CRA or GDR PU that is the first PU in
© ISO/IEC 2021 – All rights reserved  3

the layer of the bitstream in decoding order or the first PU in the layer of the bitstream that follows an EOS NAL unit in the layer in
decoding order.
3.31
CLVSS PU
PU in which the coded picture is a CLVSS picture
3.32
CLVSS picture
coded picture that is an IRAP picture with NoOutputBeforeRecoveryFlag equal to 1 or a GDR picture with
NoOutputBeforeRecoveryFlag equal to 1
3.33
coded picture
coded representation of a picture comprising VCL NAL units with a particular value of nuh_layer_id within an AU and
containing all CTUs of the picture
3.34
coded picture buffer
first-in first-out buffer containing DUs in decoding order specified in the hypothetical reference decoder
Note 1 to entry: The hypothetical reference decoder is specified in Annex C.
3.35
coded representation
data element as represented in its coded form
3.36
coded video sequence
sequence of AUs that consists, in decoding order, of a CVSS AU, followed by zero or more AUs that are not CVSS AUs,
including all subsequent AUs up to but not including any subsequent AU that is a CVSS AU
3.37
CVSS AU
IRAP AU or GDR AU for which the coded picture in each PU is a CLVSS picture
3.38
coding block
MxN block of samples for some values of M and N such that the division of a CTB into coding blocks is a partitioning
3.39
coding tree block
N×N block of samples for some value of N such that the division of a component into CTBs is a partitioning
3.40
coding tree unit
CTB of luma samples, two corresponding CTBs of chroma samples of a picture that has three sample arrays, or a CTB of
samples of a monochrome picture, and syntax structures used to code the samples
3.41
coding unit
coding block of luma samples, two corresponding coding blocks of chroma samples of a picture that has three sample
arrays in the single tree mode, or a coding block of luma samples of a picture that has three sample arrays in the dual tree
mode, or two coding blocks of chroma samples of a picture that has three sample arrays in the dual tree mode, or a
coding block of samples of a monochrome picture, and syntax structures used to code the samples
3.42
component
array or single sample from one of the three arrays (luma and two chroma) that compose a picture 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
3.43
context variable
variable specified for the adaptive binary arithmetic decoding process of a bin by an equation containing recently
decoded bins
3.44
deblocking filter
filtering process that is applied as part of the decoding process in order to minimize the appearance of visual artefacts at
the boundaries between blocks
4  © ISO/IEC 2021 – All rights reserved

3.45
decoded picture
picture produced by applying the decoding process to a coded picture
3.46
decoded picture buffer
buffer holding decoded pictures for reference, output reordering, or output delay specified for the hypothetical reference
decoder
3.47
decoder
embodiment of a decoding process
3.48
decoding order
order in which syntax elements are processed by the decoding process
3.49
decoding process
process specified in this document that reads a bitstream and derives decoded pictures from it
3.50
decoding unit
AU if DecodingUnitHrdFlag is equal to 0 or a subset of an AU otherwise, consisting of one or more VCL NAL units in an
AU and the associated non-VCL NAL units
3.51
emulation prevention byte
byte equal to 0x03 that is present within a NAL unit when the syntax elements of the bitstream form certain patterns of
byte values in a manner that ensures that no sequence of consecutive byte-aligned bytes in the NAL unit can contain a
start code prefix
3.52
encoder
embodiment of an encoding process
3.53
encoding process
process not specified in this document that produces a bitstream conforming to this document
3.54
filler data NAL units
NAL units with nal_unit_type equal to FD_NUT
3.55
flag
variable or single-bit syntax element that can take one of the two possible values: 0 and 1
3.56
frequency index
one-dimensional or two-dimensional index associated with a transform coefficient prior to the application of a transform
in the decoding process
3.57
GDR AU
AU in which there is a PU for each layer present in the CVS and the coded picture in each present PU is a GDR picture
3.58
GDR PU
PU in which the coded picture is a GDR picture
3.59
GDR picture
picture for which each VCL NAL unit has nal_unit_type equal to GDR_NUT
Note 1 to entry: The value of pps_mixed_nalu_types_in_pic_flag for a GDR picture is equal to 0. When
pps_mixed_nalu_types_in_pic_flag is equal to 0 for a picture, and any slice of the p
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