ISO/IEC 21122-4:2022

INTERNATIONAL ISO/IEC
STANDARD 21122-4
Second edition
2022-10
Information technology — JPEG XS
low-latency lightweight image coding
system —
Part 4:
Conformance testing
Technologies de l'information — Système de codage d'images léger à
faible latence JPEG XS —
Partie 4: Essais de conformité
Reference number
© ISO/IEC 2022
© ISO/IEC 2022
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© ISO/IEC 2022 – All rights reserved

Contents Page
Foreword .iv
1 Scope . 1
2 Normative references . 2
3 Terms and definitions . 2
4 Abbreviated terms . 2
5 Overview . 3
6 General description . 3
6.1 Overview . 3
6.2 Codestream syntax testing. 3
6.3 Test procedures to test decoders for conformance to ISO/IEC 21122-1 . 3
6.4 Test procedures to test decoders for conformance to ISO/IEC 21122-3 . 3
6.5 File format syntax testing . 3
6.6 Profile, level and sublevel conformance testing . 4
6.7 Buffer model conformance testing . 4
6.8 Electronic attachments . 4
7 Conformance files availability and updates . 4
Annex A (normative) Codestream syntax testing procedures . 5
Annex B (normative) Decoder testing procedures . 6
Annex C (normative) Decoder conformance tests .10
Annex D (normative) File format syntax testing procedures .15
Annex E (normative) Buffer model conformance testing .16
Annex F (informative) Attached software .19
Bibliography .21
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© ISO/IEC 2022 – All rights reserved

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 https://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 JTC 1, Information technology,
Subcommittee SC 29, Coding of audio, picture, multimedia and hypermedia information.
This second edition cancels and replaces the first edition (ISO/IEC 21122-4:2020), which has been
technically revised.
The main changes are as follows:
— reference test streams have been revised
— reference test streams for testing colour filter array (CFA) image compression have been added;
— reference test streams testing lossless coding have been added;
— reference test streams testing 4:2:0 sampled images has been added;
— a relaxed conformance point based on PSNR bounds was introduced.
A list of all parts in the ISO/IEC 21122 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 2022 – All rights reserved

INTERNATIONAL STANDARD ISO/IEC 21122-4:2022(E)
Information technology — JPEG XS low-latency lightweight
image coding system —
Part 4:
Conformance testing
1 Scope
This document specifies the framework, concepts, methodology for testing, and criteria to be achieved
to claim conformance to multiple parts of the ISO/IEC 21122 series. It lists the conformance testing
procedures.
This document specifies:
— Conformance testing procedures for decoders implementing ISO/IEC 21122-1.
— Tests to check which conformance point an ISO/IEC 21122-1 decoder conforms to, that is, whether a
decoder satisfies the error bounds required for strict or relaxed conformance.
— Conformance testing procedures for decoders implementing ISO/IEC 21122-3.
— Tests to check codestreams for conformance to ISO/IEC 21122-1. As such, it provides means to
test whether encoder implementations generate syntactically correct codestreams, and whether
codestreams generated by such implementations follow the requirements of a particular profile,
level and sublevel, and the buffer model implied by them.
— Tests to check files for conformance to ISO/IEC 21122-3.
— Conformance testing procedures that allow testing whether codestreams conform to any of the
profiles specified in ISO/IEC 21122-2.
— Conformance testing procedures that allow testing whether codestreams conform to the buffer
model specified in ISO/IEC 21122-2 as part of a profile, level and sublevel.
— Codestreams, decoded images, and error metrics to be used within the decoder testing procedures.
— A buffer model test.
— Abstract test suites.
NOTE This document does not specify:
— Testing the reconstruction of a full resolution image from a subsampled image format. In particular,
upsampling from 4:2:2 or 4:2:0 to 4:4:4 sampling is a non-normative extension and as such its testing is
beyond the scope of this document.
— Testing the conversion of the sample values reconstructed by an ISO/IEC 21122-3 decoder to the target colour
space by means of the colour specification box of ISO/IEC 21122-3.
— Testing of the composition of background and foreground for images reconstructed from ISO/IEC 21122-3
files or codestreams that contain auxiliary channels carrying opacity information.
— Testing of the interpolation of a colour filter array image to a full scale colour image; this process is not
normatively defined and beyond the scope of this document.
— Acceptance testing: the process of determining whether an implementation satisfies acceptance criteria
and enables the user to determine whether or not to accept the implementation. This includes the planning
© ISO/IEC 2022 – All rights reserved

and execution of several kinds of tests (e.g. functionality, quality, and speed performance testing) that
demonstrate that the implementation satisfies the user requirements.
— Performance testing: measures the performance characteristics of an implementation under test (IUT) such
as its throughput, responsiveness, etc. under various conditions.
— Robustness testing: the process of determining how well an implementation is able to conceal problems from
attempting to reconstruct an image from an ill-formed codestream.
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/IEC 21122-1, Information technology — JPEG XS low-latency lightweight image coding system — Part
1: Core coding system
ISO/IEC 21122-2, Information technology — JPEG XS low-latency lightweight image coding system — Part
2: Profiles and buffer models
ISO/IEC 21122-3, Information technology — JPEG XS low-latency lightweight image coding system — Part
3: Transport and container formats
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO/IEC 21122-1, ISO/IEC 21122-2,
ISO/IEC 21122-3 and the following 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
executable test suite
set of executable test cases in the form of codestreams that are input into an implementation under test
3.2
JPEG XS file
sequence of bytes encoding an image in the JXS file format
Note 1 to entry: This format is specified in ISO/IEC 21122-3.
3.3
procedure
set of steps which accomplishes one of the tasks which comprise an encoding or decoding process
3.4
test codestream set
(sub-)set of codestreams that are input to an implementation under test for a particular test purpose
4 Abbreviated terms
ASCII American Standard Code for Information Interchange
ETS executable test suite
© ISO/IEC 2022 – All rights reserved

IUT implementation under test
PSNR peak signal to noise ratio
TCS test codestream set
5 Overview
The conformance files including codestreams, reference decoded images, descriptive files and auxiliary
software to facilitate testing are provided at https:// standards .iso .org/ iso -iec/ 21122/ -4/ ed -2/ en, in
compressed form. File locations given in this document are expressed relative to the top level directory
tree within this compressed file. A Unix style file structure and delimiters are assumed.
This document contains instructions for the use of these files.
6 General description
6.1 Overview
The ISO/IEC 21122 series, also known as JPEG XS, consists of multiple parts of which for ISO/IEC 21122-1
describes the core coding system and the syntax of a codestream, for ISO/IEC 21122-2 describes
profiles and buffer models and for ISO/IEC 21122-3 describes transport and container formats. This
document defines test suites for decoder conformance tests for ISO/IEC 21122-1, ISO/IEC 21122-2 and
ISO/IEC 21122-3.
6.2 Codestream syntax testing
The procedures of Anne
...