ISO/IEC 15444-17:2023

INTERNATIONAL ISO/IEC
STANDARD 15444-17
First edition
2023-06
Information technology — JPEG 2000
image coding system —
Part 17:
Extensions for coding of discontinuous
media
Technologies de l'information — Système de codage d'images JPEG
2000 —
Partie 17: Extensions pour le codage des supports discontinus
Reference number
© ISO/IEC 2023
© ISO/IEC 2023
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Foreword
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© ISO/IEC 2023 – All rights reserved iii

INTERNATIONAL STANDARD ISO/IEC 15444-17
RECOMMENDATION ITU-T T.816 (V1)
Information technology – JPEG 2000 image coding system:
Extensions for coding of discontinuous media
Summary
Rec. ITU-T T.816 | ISO/IEC 15444-17 provides extensions of the scalable image coding tools described in
Rec. ITU-T T.800 | ISO/IEC 15444-1 and Rec. ITU-T T.801 | ISO/IEC 15444-2, of two types. First, new wavelet-like
image transforms known as "breakpoint-dependent" transforms are defined, whose underlying basis functions can be
discontinuous at defined locations within the image component to which they are applied. Second, new scalable coding
tools are described for a new type of image component known as a "breakpoint component", which provides a successively
refinable and hierarchical description of the breakpoint locations used by the breakpoint-dependent transforms. Any non-
initial component or components within a codestream conforming to this Recommendation | International Standard can be
breakpoint components and any of the components in the codestream other than breakpoint components can use a
breakpoint-dependent transform that depends upon one of the breakpoint components in the same codestream. These new
tools together allow for the scalable coding of imagery that naturally exhibits strong discontinuities in the spatial domain.
An important example of such imagery is depth maps.
This Recommendation was developed jointly with ISO/IEC JTC 1/SC 29/WG 1 (JPEG) and is common text with
ISO/IEC 15444-17.
History
*
Edition Recommendation Approval Study Group Unique ID
1.0 ITU-T T.816 (V1) 2023-02-13 16 11.1002/1000/15206
*
To access the Recommendation, type the URL http://handle.itu.int/ in the address field of your web browser,
followed by the Recommendation's unique ID. For example, http://handle.itu.int/11.1002/1000/11830-en.
iv Rec. ITU-T T.816 (V1) (02/2023)
© ISO/IEC 2023 – All rights reserved

FOREWORD
The International Telecommunication Union (ITU) is the United Nations specialized agency in the field of
telecommunications, information and communication technologies (ICTs). The ITU Telecommunication
Standardization Sector (ITU-T) is a permanent organ of ITU. ITU-T is responsible for studying technical,
operating and tariff questions and issuing Recommendations on them with a view to standardizing
telecommunications on a worldwide basis.
The World Telecommunication Standardization Assembly (WTSA), which meets every four years, establishes
the topics for study by the ITU-T study groups which, in turn, produce Recommendations on these topics.
The approval of ITU-T Recommendations is covered by the procedure laid down in WTSA Resolution 1.
In some areas of information technology which fall within ITU-T's purview, the necessary standards are
prepared on a collaborative basis with ISO and IEC.
NOTE
In this Recommendation, the expression "Administration" is used for conciseness to indicate both a
telecommunication administration and a recognized operating agency.
Compliance with this Recommendation is voluntary. However, the Recommendation may contain certain
mandatory provisions (to ensure, e.g., interoperability or applicability) and compliance with the
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obligatory language such as "must" and the negative equivalents are used to express requirements. The use of
such words does not suggest that compliance with the Recommendation is required of any party.
INTELLECTUAL PROPERTY RIGHTS
ITU draws attention to the possibility that the practice or implementation of this Recommendation may involve
the use of a claimed Intellectual Property Right. ITU takes no position concerning the evidence, validity or
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© ITU 2023
All rights reserved. No part of this publication may be reproduced, by any means whatsoever, without the prior
written permission of ITU.
Rec. ITU-T T.816 (V1) (02/2023) v
© ISO/IEC 2023 – All rights reserved

CONTENTS
Page
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Abbreviations . 2
5 5 Conventions . 3
6 Conformance . 3
6.1 Codestream conformance . 3
6.2 Decoder. 3
7 Breakpoint component structure. 4
7.1 Breakpoint components and the reference grid. 4
7.2 Division of breakpoint resolutions into cells, arcs and the CL band. 4
7.3 Division of breakpoint resolutions into precincts and code-blocks . 5
7.4 Root and non-root arc breakpoint associations . 7
7.5 Breakpoint values and vertices . 8
8 Breakpoint-dependent spatial wavelet transformation . 10
8.1 Overview . 10
8.2 TriBPT-dependent irreversible transforms . 11
8.2.1 Introduction . 11
8.2.2 Arcs with tb=0 . 12
8.2.3 Arcs with tb=3 . 13
8.2.4 Arcs with tb=2 . 13
8.2.5 Arcs with tb=1 . 17
8.3 TriBPT-dependent reversible transforms . 21
8.3.1 Arcs with tb=0 . 22
8.3.2 Arcs with tb=3 . 22
8.3.3 Arcs with tb=2 . 22
8.3.4 Arcs with tb=1 . 22
8.4 QuadBPT-dependent transforms. 23
8.4.1 Introduction . 23
8.4.2 BD_2D_SR phase 1 . 24
8.4.3 BD_2D_SR phase 2 . 26
9 Decoding of breakpoint code-blocks . 28
9.1 Embedded bit-plane decoding of breakpoints. 28
9.2 Inter-band coding mode (BPT_INTER) . 29
9.3 Cell-based scanning patterns and CBAP-based block flipping. 30
9.4 QuadBPT decoding procedures . 32
9.4.1 MQ Coder contexts and initial states for QuadBPT decoding . 32
9.4.2 Derivation of context labels for QuadBPT CL band significance coding passes . 33
9.4.3 Non-root significance decoding for QuadBPT CL code-blocks . 35
9.4.4 Root significance decoding for QuadBPT CL code-blocks . 36
9.4.5 Root significance decoding for QuadBPT LL code-blocks . 37
9.4.6 Position refinement decoding for QuadBPT code-blocks . 37
9.5 TriBPT decoding procedures . 38
9.5.1 MQ Coder contexts and initial states for TriBPT decoding . 38
9.5.2 Derivation of context labels for TriBPT CL band significance coding passes. 39
9.5.3 Non-root significance decoding for TriBPT CL code-blocks . 42
9.5.4 Root significance decoding for TriBPT CL code-blocks . 43
9.5.5 Root significance decoding for TriBPT LL code-blocks . 44
9.5.6 Position refinement decoding for TriBPT code-blocks . 45
9.6 Quality layers and packets for breakpoint components . 45
10 Reconstruction of breakpoint components . 47
10.1 Overview . 47
10.2 Direct induction step . 47
10.2.1 Introduction . 47
10.2.2 Extrapolation Qualifier for TriBPT direct induction. 48
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Page
10.3 QuadBPT spatial induction . 49
10.3.1 Introduction . 49
10.4 TriBPT spatial induction. 51
10.4.1 TriBPT induction modes and corner notation . 51
10.4.2 4-arc mode . 51
10.4.3 3-arc mode . 52
10.4.4 Extrapolation qualifier for TriBPT spatial induction . 53
10.4.5 Rounding policies for TriBPT spatial induction . 56
10.4.6 Image boundary handling for TriBPT . 56
(This annex forms an integral part of this Recommendation | International Standard.) – Codestream syntax . 58
A.1 General . 58
A.2 SIZ marker segment. 58
A.3 CAP marker segment . 58
A.4 Hierarchical data type (HDT) marker segment . 59
A.5 COD and COC marker segments . 59
(This annex does not form an integral part of this Recommendation | International Standard) –
Hierarchical breakpoint encapsulation and raw file format . 62
B.1 General . 62
B.2 Raster organization of breakpoints . 62
B.3 16- and 32-bit packed breakpoint values . 63
B.4 A raw file format for breakpoints . 64
Bibliography . 67
List of Tables
Page
Table 1 – Constraints on PPx and PPy precinct size parameters breakpoint components . 6
Table 2 – MQ coder contexts for QuadBPT CL code-block decoding passes. State index values correspond
to the Qe values and probability estimation transitions tabulated in Rec. ITU-T T.800 | ISO/IEC 15444-1 . 33
Table 3 – Context labels from Table 2 that are used for QuadBPT LL code-block decoding passes . 33
Table 4 – MQ coder contexts for TriBPT CL code-block decoding passes. State index values correspond to the Qe
values and probability estimation transitions tabulated in Rec. ITU-T T.800 | ISO/IEC 15444-1 . 38
Table 5 – Context labels from Table 4 that are used for TriBPT LL code-block decoding passes. 38
Table A.1 – Extensions and constraints to marker segments specified in Rec. ITU-T T.800 | ISO/IEC 15444-1
and new marker segments specified in this Recommendation | International Standard . 58
Table A.2 – Ccap Syntax and Semantics . 58
Table A.3 – Hierarchical data type parameter values . 59
i
Table A.4 – Allowed values for Ihdt . 59
Table A.5 – Scod and Scoc semantics for bit 5 . 60
Table A.6 – SXcod bit fields specified by this Recommendation | International Standard . 60
Table A.7 – Allowed values for the SEcod field . 61
Table A.8 – Transformation for the SPcod and SPcoc parameters when Dc≠0. 61
vii
Rec. ITU-T T.816 (V1) (02/2023)
© ISO/IEC 2023 – All rights reserved

List of Figures
Page
Figure 1 – Arc arrangements within a single 2-span. A 𝟐×𝟐 cell is shown here with solid grid-points.
See Figure 2 for other geometric relationships between cells and 2-spans . 5
Figure 2 – Cell-span geometry for each of the four possible code-block anchor points . 5
Figure 3 – Root arc (dotted lines) and non-root arcs (solid lines). 8
Figure 4 – Possible break locations (tick-points) at the finest resolution, with 𝑭𝑩=𝟐, shown for the QuadBPT case.
Also shows the mapping of vertices with precision 𝑷𝒃 to tick-points . 9
Figure 5 – Stages of the breakpoint dependent inverse discrete wavelet transform . 10
Figure 6 – Interleaving of sub-band coefficients to a triangular grid for a given resolution r . 12
Figure 7 – Update step examples for TriBPT-LR arrangement . 12
Figure 8 – Predict step examples for a horizontal arc . 12
Figure 9 – Example of direct induction of a breakpoint . 14
Figure 10 – Example illustrating spatially induced breaks . 14
Figure 11 – Example of a spatially induced breakpoint on a non-root arc for the TriBPT-LR arrangement. 15
Figure 12 – Examples showing base-arc 𝒃𝒔𝒂 and gradients 𝑮𝒃𝒔𝒂 and 𝑮𝒘𝒅𝒈 along with corresponding binary flags
ORN and 𝑫𝑹𝑪𝑻𝑵𝑿_𝑭𝑳𝑨𝑮 𝒊𝒏𝒅𝒖𝒄𝒆𝒅 for root arcs . 16
Figure 13 – Example showing base-arc 𝒃𝒔𝒂 and gradients 𝑮𝒃𝒔𝒂 and 𝑮𝒘𝒅𝒈 along with corresponding binary flags
ORN and 𝑫𝑹𝑪𝑻𝑵𝑿_𝑭𝑳𝑨𝑮 𝒊𝒏𝒅𝒖𝒄𝒆𝒅 for diagonal non-root arc containing a spatially induced break . 16
Figure 14 – Examples of arcs 𝒑𝒓𝒍 parallel in orientation to root arcs centred at 𝒑 and containing a spatially induced
break. Gradient calculated across arc 𝒑𝒓𝒍 is denoted as 𝑮𝒑𝒓𝒍 . 19
Figure 15 – Example of arc 𝒑𝒓𝒍 parallel to the non-root arc centred and at 𝒑 and containing a spatially induced break.
Corresponding gradient across arc 𝒑𝒓𝒍 is shown as 𝑮𝒑𝒓𝒍 . 19
Figure 16 – Algorithm for determining the gradient 𝑮𝒃 based on validity flags VALID_WDG and VALID_PRL
and corresponding attributes . 20
Figure 17 – Parent 4-span arrangement at resolution 𝒓𝒓𝒕=𝒓−𝟏 for arc 𝒂 at resolution 𝒓 and centred at 𝒑 . 21
Figure 18 – Algorithm for determining the gradient 𝑮𝒃 for the reversible transform, based on validity flags
VALID_WDG and VALID_PRL and corresponding attributes . 23
Figure 19 – Interleaving of sub-band coefficients to a quadrilateral grid for a given resolution r . 23
Figure 20 – Phase 1 update step for (even, even) location 𝟐𝒏,𝟐𝒎 . 24
Figure 21 – Phase 1 update step for (even, odd) location 𝟐𝒏,𝟐𝒎+𝟏 and (odd, even) location 𝟐𝒏+𝟏,𝟐𝒎 . 25
Figure 22 – Phase 1 predict step for (odd, odd) location 𝟐𝒏+𝟏,𝟐𝒎+𝟏 with source locations of 𝑰𝒄,𝒓∗shown . 26
Figure 23 – Phase 2 update step for (even, even) location 𝟐𝒏,𝟐𝒎 . 27
Figure 24 – Phase 2 predict step examples . 28
Figure 25 – Canonical scanning pattern used for the significance coding passes of CL band code-blocks in a
QuadBPT component. In this case, missing cells within a 𝟐×𝟐 group are not included in the scan . 30
Figure 26 – Canonical scanning pattern used for the significance coding passes of CL band code-blocks in TriLR
components. Arcs belonging to cells that lie beyond the code-block boundaries are included in the significance
coding passes . 31
Figure 27 – Canonical scanning pattern used for the significance coding passes of CL band code-blocks in TriRL
components. Arcs belonging to cells that lie beyond the code-block boundaries are included in the significance
coding passes . 31
Figure 28 – Neighbouring cells and arcs involved in forming coding contexts for QuadBPT significance
decoding in CL band code-blocks . 34
Figure 29 – Neighbouring cells and arcs involved in forming coding contexts for TriLR significance
decoding in CL band code-blocks . 39
viii Rec. ITU-T T.816 (V1) (02/2023)
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Page
Figure 30 – Neighbouring cells and arcs involved in forming coding contexts for TriRL significance
decoding in CL band code-blocks . 40
Figure 31 – Breakpoint synthesis stages . 47
Figure 32 – Relationship between non-root and parent arcs during direct induction in synthesis stage 𝒓,
shown for the case of horizontal arcs. 48
Figure 33 – Rounding policies used in QuadBPT spatial induction, showing different induction examples
in three of the four 2-spans within a 4-span . 50
Figure 34 – Arc and corner labels for the TriBPT-LR arrangement . 51
Figure 35 – 4-arc mode spatial induction examples for the TriBPT-LR arrangement . 52
Figure 36 – 3-arc mode spatial induction examples for the TriBPT-LR arrangement . 53
Figure 37 – Example of intersection points, arcs and grid-lines required for determining the extrapolation
qualifier for a spatially induced break . 55
Figure 38 – Examples of rounding policy for 3-arc mode spatial induction when the inducing line intersects
the root arc X at its centre. The direction of rounding is highlighted by the black arrows . 56
Figure A.1 – Hierarchical data type syntax . 59
Figure A.2 – Coding style default syntax . 60
Figure A.3 – Coding style component syntax . 60
Figure B.1 – Bit fields within 16- and 32-bit packed breakpoint representations. The most significant bit
of the 16- or 32-bit integer, as appropriate, is shown at the top of the figure, while the least significant bit
appears at the bottom . 64
Rec. ITU-T T.816 (V1) (02/2023) ix
© ISO/IEC 2023 – All rights reserved

Introduction
The JPEG 2000 core coding system specified in Rec. ITU-T T.800 | ISO/IEC 15444-1 and its extensions specified in Rec.
ITU-T T.801 | ISO/IEC 15444-2 provide a suite of scalable coding technologies that are particularly suitable for
photographic media, but less effective at coding media with hard discontinuities. An important example of such media is
depth imagery, where each image sample is related to the length of the 3D line segment between the corresponding scene
point and the camera. Depth imagery includes stereo disparity maps, where sample values are reciprocally related to
depth. Another example of media with strong discontinuities is optical flow data, where each sample location is a two-
dimensional vector. In these examples, discontinuities arise naturally at the boundaries of scene objects. Moreover, where
this happens, intermediate values that might be obtained by bandlimited image resampling or interpolation operations
have no physical meaning – i.e., they do not correspond to the depth or flow vector of any object in the original scene.
The discrete wavelet transform (DWT) employed in JPEG 2000 is not well suited to the coding of such media, both from
the perspective of coding efficiency and considering the nature of distortions that result when the wavelet sub-band
samples are quantized.
To address these challenges, this Recommendation | International Standard introduces alternate "breakpoint-dependent"
spatial wavelet transforms that are dependent on an auxiliary image component, known as a "breakpoint component."
This Recommendation | International Standard also introduces scalable coding technologies for breakpoint components.
Any non-initial component or components within the codestream can be designated as breakpoint components, allowing
them to be used as the source of breakpoints for other components, or tiles thereof, which specify the use of breakpoint-
dependent wavelet transforms.
This Recommendation | International Standard specifies two different types of breakpoint components, designated as
"QuadBPT" and "TriBPT" components, with associated decoding and synthesis tools. Associated with the type of
breakpoint component is a corresponding breakpoint-dependent wavelet transform, with its synthesis tools. The
reconstruction procedures described in this Recommendation | International Standard produce individual sample values.
In the TriBPT case, it is possible instead to directly reconstruct a deformable triangular mesh, whose complexity is related
to the number of non-zero wavelet coefficients and the number of decoded breaks, which are identified here as "vertices."
In each case, breakpoints introduce tears in the mesh. This feature can be valuable in computer graphics applications,
where the mesh elements provide a more convenient description of the data than individual samples.
The normative material of this Recommendation | International Standard is contained within the main body together with
Annex A. Additionally, Annex B describes ways of encapsulating breakpoint data within a linear file structure, that can
be used as a source for encoding and a target for decoding procedures.
x Rec. ITU-T T.816 (V1) (02/2023)
© ISO/IEC 2023 – All rights reserved

INTERNATIONAL STANDARD
ITU-T RECOMMENDATION
Information technology – JPEG 2000 image coding system:
Extensions for coding of discontinuous media
1 Scope
This Recommendation | International Standard defines QuadBPT and TriBPT image components, collectively known as
"breakpoint components", and specifies decoding and reconstruction procedures for recovering breakpoint component
sample values from the codestream. This Recommendation | International Standard also specifies "breakpoint-dependent"
spatial wavelet transforms that can be used in place of the transforms specified in Recommendation ITU-T T.800 |
ISO/IEC 15444-1 for selected image components or tile-components. Extensions to the codestream syntax of
Rec. ITU-T T.800 | ISO/IEC 15444-1 are specified to enable the identification of breakpoint components, of components
that can use a breakpoint-dependent spatial wavelet transform, and the association of breakpoint components with such
breakpoint-dependent wavelet transforms.
2 Normative references
The following Recommendations and International Standards contain provisions which, through reference in this text,
constitute provisions of this Recommendation | International Standard. At the time of publication, the editions indicated
were valid. All Recommendations and Standards are subject to revision, and parties to agreements based on this
Recommendation | International Standard are encouraged to investigate the possibility of applying the most recent edition
of the Recommendations and Standards listed below. Members of IEC and ISO maintain registers of currently valid
International Standards. The Telecommunication Standardization Bureau of the ITU maintains a list of currently valid
ITU-T Recommendations.
2.1 Identical Recommendations | International Standards
– Recommendation ITU-T T.800 (2019) | ISO/IEC 15444-1:2019, Information technology – JPEG 2000
image coding system: Core coding system.
– Recommendation ITU-T T.801 (2021) | ISO/IEC 15444-2:2021, Information technology – JPEG 2000
image coding system: Extensions.
3 Definitions
3.1 Terms defined elsewhere
For the purposes of this Recommendation | International Standard, the terms and definitions given in Rec. ITU-T T.800 |
ISO/IEC 15444-1 apply.
ITU, ISO and IEC maintain terminological databases for use in standardization at the following addresses:
– ITU Terms and definitions database: available at https://www.itu.int/go/terms
– ISO Online browsing platform: available at https://www.iso.org/obp
– IEC Electropedia: available at http://www.electropedia.org/
3.2 Terms defined in this Recommendation | International Standard
This Recommendation | International Standard defines the following terms:
3.2.1 2-span: Square configuration of width 2 and height 2, with 9 grid-points, such that the four corner grid-points
all have coordinates that are divisible by 2.
3.2.2 4-span: 2×2 configuration of 2-spans (3.2.1), involving 25 grid-points, such that the four corner grid-points
all have coordinates that are divisible by 4.
3.2.3 ambivalent break: Induced break (3.2.5) that has insufficient precision to determine whether the break occurs
in the first or second half of the arc.
3.2.4 arc: Line segment connecting grid-points with even valued coordinates at any resolution of a breakpoint tile-
component.
Rec. ITU-T T.816 (V1) (02/2023) 1
© ISO/IEC 2023 – All rights reserved

3.2.5 break: Explicitly decoded or inferred location within an arc (3.2.4) that indicates a boundary within an image
component.
NOTE 1 – Breaks modify the behaviour of breakpoint-dependent transforms on that other image component.
NOTE 2 – An arc has at most one break.
3.2.6 breakpoint: Data structure consisting of break type, location and precision information for an arc (3.2.4).
NOTE – Type-0 breakpoints have no break at all.
3.2.7 breakpoint component: JPEG 2000 codestream image component that represents arc breakpoint (3.2.6)
information.
3.2.8 breakpoint tile-component: All the breakpoints of a given tile, within a breakpoint component (3.2.7).
3.2.9 cell: 2×2 configuration of grid-points within a resolution of a breakpoint tile-component (3.2.8).
NOTE – Cells belong to a well-defined partition that is anchored at the global code-block anchor point.
3.2.10 CL band: The sole sub-band associated with each resolution of a breakpoint tile-component (3.2.8) other than
the lowest resolution.
3.2.11 code-block anchor point: Origin of the coding partitions, which is one of the locations (0,0), (0,1), (1,0) or
(1,1).
[SOURCE: Rec. ITU-T T.801 | ISO/IEC 15444-2]
3.2.12 directly induced break: Break (3.2.5) on an arc that is inferred from a break on a parent arc.
3.2.13 extrapolation qualifier: 2-bit quantity 𝑒 which controls the way gradients are obtained for extrapolation
𝑏
within a TriBPT-dependent transformation.
3.2.14 indefinite break: Induced break (3.2.15) on an arc that is derived from one or more ambivalent breaks (3.2.3),
such that there is insufficient precision to determine whether any break at all exists on the arc.
3.2.15 induced break: Break (3.2.5) on an arc that is inferred from breaks on other arcs.
3.2.16 induction block: Condition on an arc (3.2.4) that is explicitly recovered from the decoding of breakpoint code-
blocks, indicating that no break (3.2.5) shall be induced on that arc.
3.2.17 non-root arc: Arc (3.2.4) that is not a root arc.
3.2.18 parent arc: Arc (3.2.4) at depth 𝑑+1 in the breakpoint decomposition that contains an arc at depth 𝑑.
NOTE – At most two arcs at depth 𝑑 can have the same parent at depth 𝑑+1.
3.2.19 pass-complete: Code-block within a breakpoint component for which one or more coding passes are found
within the codestream packets and the last such coding pass is identified as completing the code-block's representation
via the packet header signalling mechanisms.
3.2.20 QuadBPT: Breakpoint (3.2.6) arrangement involving only horizontal and vertical arcs (3.2.4).
3.2.21 root arc: Arc (3.2.4) that is not contained within any arc projected from the next lower resolution of a breakpoint
tile-component (3.2.8), regardless of whether that next lower resolution actually exists within the tile-component's
resolution hierarchy.
3.2.22 spatially induced break: Induced break (3.2.15) that is inferred from breaks on non-parent arcs.
3.2.23 tick-point: Possible break (3.2.5) location along an arc.
3.2.24 TriBPT: Breakpoint (3.2.6) arrangement involving horizontal, vertical and diagonal arcs (3.2.4).
3.2.25 TriBPT-LR: TriBPT (3.2.24) breakpoint arrangement involving diagonal arcs that run from the top-left to the
bottom-right of a 2-span within any resolution of a breakpoint tile-component (3.2.8).
3.2.26 TriBPT-RL: TriBPT (3.2.24) breakpoint arrangement involving diagonal arcs that run from the top-right to the
bottom-left of a 2-span within any resolution of a breakpoint tile-component (3.2.8).
3.2.27 vertex: Explicitly coded break (3.2.5) location.
3.2.28 zero-complete: Code-block within a breakpoint component (3.2.7) that makes no contribution to any
codestream packet and is identified as complete by the first packet header of its precinct.
4 Abbreviations
For the purposes of this Recommendation | International Standard, the following abbreviations apply:
BD-IDWT Breakpoint-Dependent Inverse Discrete Wavelet Transformation
2 Rec. ITU-T T.816 (V1) (02/2023)
© ISO/IEC 2023 – All rights reserved

BGP Base Grid Point
BIL Break Inducing Line
BIP Base Intersection Point
BLN Base Line
BSA Base Arc
CBAP Code-Block Anchor Point
DIB Directly Induced Breaks
HDT Hierarchical Data Type
HGP Horizontal Grid-Point
MPS More Probable Symbol
RAC Round Away from Centre
RTN Round to Nearest
SBR Source Breaks
SPB Spatially induced Break
TPS Tick-Points
VMR Vertex Mapping Rule
VRT Vertex
WDA Wedge Area
5 Conventions
This Recommendation | International Standard uses the following conventions:
• CBAP (𝒛 ,𝒛 ) – code-block anchor point
𝒙 𝒚
• MAX_WDG – maximum search distance for the gradient extrapolation algorithm used during the TriBPT-
dependent prediction step associated with a spatially induced arc.
• BPT_INTER – binary flag that is 1 if code-blocks of a breakpoint component use the inter-band coding mode
and 0 if the code-blocks of a breakpoint component are coded without reference to any other code-block data.
6 Conformance
6.1 Codestream conformance
A codestream conforming to this Specification shall conform to Annex A.
6.2 Decoder
A decoder conforming to this Specification shall process a codestream that conforms to this Specification in the manner
specified in Rec. ITU-T T.800 | ISO/IEC 15444-1 together with any additional signalled capability specified in this
Specification, with the exception of breakpoint components and tile-components that identify the use of a breakpoint-
dependent spatial wavelet transform, in which case the following shall apply:
▪ breakpoint components shall have the structure specified in clause 7;
▪ tile-components that use a breakpoint-dependent spatial wavelet transform shall be processed in accordance with
clause 8; and
▪ breakpoint components shall be reconstructed from breakpoint code-blocks in accordance with clause 10, where
breakpoint code-blocks are decoded in accordance with clause 9.
This Recommendation | International Standard is compatible with the coding technologies
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