ISO/IEC PRF 21122-5
(Main)Information technology — JPEG XS low-latency lightweight image coding system — Part 5: Reference software
Information technology — JPEG XS low-latency lightweight image coding system — Part 5: Reference software
This document contains the reference software of the ISO/IEC 21122 series. It acts as a guideline for implementation and as a reference for conformance testing.
Technologies de l'information — Système de codage d’images léger à faible latence JPEG XS — Partie 5: Logiciel de référence
General Information
Relations
Standards Content (Sample)
International
Standard
ISO/IEC 21122-5
Third edition
Information technology — JPEG
XS low-latency lightweight image
coding system —
Part 5:
Reference software
Technologies de l'information — Système de codage d’images
léger à faible latence JPEG XS —
Partie 5: Logiciel de référence
PROOF/ÉPREUVE
Reference number
ISO/IEC 21122-5:2025(en) © ISO/IEC 2025
ISO/IEC 21122-5:2025(en)
© ISO/IEC 2025
All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may
be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting on
the internet or an intranet, without prior written permission. Permission can be requested from either ISO at the address below
or ISO’s member body in the country of the requester.
ISO copyright office
CP 401 • Ch. de Blandonnet 8
CH-1214 Vernier, Geneva
Phone: +41 22 749 01 11
Email: copyright@iso.org
Website: www.iso.org
Published in Switzerland
PROOF/ÉPREUVE
© ISO/IEC 2025 – All rights reserved
ii
ISO/IEC 21122-5:2025(en)
Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Reference software . 1
4.1 General .1
4.2 Purpose .2
4.3 Examples of use .2
5 Copyright, licensing and intellectual property . 3
Annex A (informative) Building the reference software . 4
Annex B (informative) Image file formats supported by the reference software . 5
Annex C (informative) Using the reference software . 9
Bibliography . 14
PROOF/ÉPREUVE
© ISO/IEC 2025 – All rights reserved
iii
ISO/IEC 21122-5:2025(en)
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).
ISO and IEC draw attention to the possibility that the implementation of this document may involve the
use of (a) patent(s). ISO and IEC take no position concerning the evidence, validity or applicability of any
claimed patent rights in respect thereof. As of the date of publication of this document, ISO and IEC had not
received notice of (a) patent(s) which may be required to implement this document. However, implementers
are cautioned that this may not represent the latest information, which may be obtained from the patent
database available at www.iso.org/patents and https://patents.iec.ch. ISO and IEC shall not be held
responsible for identifying any or all such patent rights.
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 third edition cancels and replaces the second edition (ISO/IEC 21122-5:2022), which has been
technically revised.
The main changes are as follows:
— the reference software has been updated.
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.
PROOF/ÉPREUVE
© ISO/IEC 2025 – All rights reserved
iv
ISO/IEC 21122-5:2025(en)
Introduction
This document is part of a series of standards for a low-latency lightweight image coding system, denoted
JPEG XS. It provides the software reference implementation of ISO/IEC 21122-1 and ISO/IEC 21122-2. It has
been successfully compiled and tested on various operating systems at the time of writing. This reference
software implementation includes both encoder and decoder functionality. It is important to note that this
reference software implementation represents just one way of implementing JPEG XS. This implementation
can serve as a validation anchor to other implementations.
No guarantee of the quality that will be achieved by an encoder is provided by its conformance to
ISO/IEC 21122-1 and ISO/IEC 21122-2, as the conformance is only defined in terms of specific constraints
imposed on the syntax of the generated codestream. In particular, while sample encoder software
implementations can suffice to provide some illustrative examples of which quality can be achieved within
the ISO/IEC 21122 series, they provide neither an assurance of minimum guaranteed image encoding quality
nor maximum achievable image encoding quality.
Similarly, the computation resource characteristics in terms of program or data memory usage, execution
speed, etc. of sample software encoder or decoder implementations should not be construed as a
representative of the typical, minimal or maximal computational resource characteristics to be exhibited by
implementations of the ISO/IEC 21122 series.
PROOF/ÉPREUVE
© ISO/IEC 2025 – All rights reserved
v
International Standard ISO/IEC 21122-5:2025(en)
Information technology — JPEG XS low-latency lightweight
image coding system —
Part 5:
Reference software
1 Scope
This document contains the reference software of the ISO/IEC 21122 series. It acts as guidance for
implementation of the ISO/IEC 21122 seriesand as a reference for conformance testing.
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
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO/IEC 21122-1 and
ISO/IEC 21122-2 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/
4 Reference software
4.1 General
In addition to the main text, including Annexes A, B and C, the reference software is available at https://
standards .iso .org/ iso -iec/ 21122/ -5/ ed -3/ en/ .
Annex A provides guidelines on how to build the provided reference software.
Annex B describes input and output image file formats that are supported by the provided reference
software.
Annex C provides guidelines on how to use the reference decoder and encoder.
PROOF/ÉPREUVE
© ISO/IEC 2025 – All rights reserved
ISO/IEC 21122-5:2025(en)
4.2 Purpose
The purpose of this document is to provide the following:
— a reference decoder software implementation, capable of decoding codestreams that conform to
ISO/IEC 21122-1, or to both ISO/IEC 21122-1 and ISO/IEC 21122-2;
— a sample encoder software implementation, capable of producing codestreams that conform to
ISO/IEC 21122-1, or to both ISO/IEC 21122-1 and ISO/IEC 21122-2.
The use of this reference software is not required for making an implementation of an encoder or decoder in
conformance to any of the parts of the ISO/IEC 21122 series. Requirements established in ISO/IEC 21122-1
and ISO/IEC 21122-2 shall take precedence over the behaviour of the reference software.
The reference decoder software generates the normative output of the decoding process specified by
ISO/IEC 21122-1. The output of the reference decoder satisfies the requirements of the strict conformance
point of ISO/IEC 21122-4. It therefore allows conformance testing by means of comparing the output of a
candidate implementation by that of the reference software specified in this document. Conformance testing
is specified in ISO/IEC 21122-4. The reference decoder software can also be used to validate the syntactic
correctness of a codestream by attempting to decode a candidate codestream with the reference software.
The reference software does not implement the file format functionality of ISO/IEC 21122-3.
4.3 Examples of use
Some examples of use for the reference decoder software implementations are as follows:
— as an illustration of how to perform the decoding processes specified in ISO/IEC 21122-1;
— as the starting basis for the implementation of a decoder that conforms to ISO/IEC 21122-1;
— for testing the conformance of a decoder implementation to ISO/IEC 21122-1 with the procedures and
details on reference testing specified in ISO/IEC 21122-4;
— for (non-exhaustive) testing of the conformance of a codestream (or file) to the constraints specified in
ISO/IEC 21122-1.
If there is no detection of non-conformance by the reference software implementation, this should not
be considered as definite proof that the codestream under testing meets all constraints required for
conformance to ISO/IEC 21122-1 or ISO/IEC 21122-2. In fact, ISO/IEC 21122-4 defines additional testing
procedures that can be used to test a codestream for conformance to ISO/IEC 21122-1 and ISO/IEC 21122-2,
such as testing the conformance to the buffer models specified therein.
Some examples of use for a sample encoder software are as follows:
— as an illustration of how to implement an encoding process that produces codestreams that are
conforming to ISO/IEC 21122-1 and ISO/IEC 21122-2;
— as a starting point for an implementation of an encoder that conforms to ISO/IEC 21122-1 and
ISO/IEC 21122-2;
— as a means of generating codestreams conforming to ISO/IEC 21122-1 and ISO/IEC 21122-2 for testing
purposes;
— as a means of demonstrating and evaluating examples of the quality that can be achieved by an encoding
process that conforms to ISO/IEC 21122-1 and ISO/IEC 21122-2.
It is not recommended to use the reference software in a production environment, as it lacks proper
protection mechanisms against memory corruption and code execution exploits.
PROOF/ÉPREUVE
© ISO/IEC 2025 – All rights reserved
ISO/IEC 21122-5:2025(en)
5 Copyright, licensing and intellectual property
The reference software was originally developed by the parties indicated in the file LICENSE.md within the
package forming a part of this document, over the course of development of this document. ISO/IEC draws
the attention of the users of this software to the licence terms and conditions specified in the same LICENSE.
md file.
PROOF/ÉPREUVE
© ISO/IEC 2025 – All rights reserved
ISO/IEC 21122-5:2025(en)
Annex A
(informative)
Building the reference software
A.1 Retrievi
...
ISO/IEC/DIS 21122-5:2025(en)
ISO/IEC/JTC 1/SC 29/WG 1
Secretariat: JISC
Third edition
Date: 2025-05-2108-15
Information technology — JPEG XS low-latency lightweight image coding system — Part 5:
Reference software
Technologies de l'information — Système de codage d’images léger à faible latence JPEG XS — Partie 5:
Logiciel de référence
ISO/IEC/DIS 21122-5:2025(en)
© ISO/IEC 2025
All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part
of this publication may be reproduced or utilized otherwise in any form or by any means, electronic or
mechanical, including photocopying, or posting on the internet or an intranet, without prior written
permission. Permission can be requested from either ISO at the address below or ISO’s member body in
the country of the requester.
ISO copyright office
CP 401 • Ch. de Blandonnet 8
CH-1214 Vernier, Geneva
Phone: +41 22 749 01 11
Email: copyright@iso.org
Website: www.iso.org
Published in Switzerland
© ISO/IEC 2025 – All rights reserved
ii
ISO/IEC/DIS 21122-5:2025(en)
Contents
Foreword . iv
Introduction . v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Reference software . 1
4.1 General . 1
4.2 Purpose . 1
4.3 Examples of use . 2
5 Copyright, licensing and intellectual property . 3
Annex A (informative) Building the reference software . 4
Annex B (informative) Image file formats supported by the reference software . 5
Annex C (informative) Using the reference software . 9
Bibliography . 14
Foreword . iv
Introduction . v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Reference software . 1
4.1 General . 1
4.2 Purpose . 1
4.3 Examples of use . 2
5 Copyright, licensing and intellectual property . 3
Annex A (informative) Building the reference software . 4
Annex B (informative) Image file formats supported by the reference software . 5
Annex C (informative) Using the reference software . 9
Bibliography . 14
© ISO/IEC 2025 – All rights reserved
iii
ISO/IEC/DIS 21122-5:2025(en)
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).
ISO and IEC draw attention to the possibility that the implementation of this document may involve the
use of (a) patent(s). ISO and IEC take no position concerning the evidence, validity or applicability of any
claimed patent rights in respect thereof. As of the date of publication of this document, ISO and IEC had
not received notice of (a) patent(s) which may be required to implement this document. However,
implementers are cautioned that this may not represent the latest information, which may be obtained
from the patent database available at www.iso.org/patents and https://patents.iec.ch. ISO and IEC shall
not be held responsible for identifying any or all such patent rights.
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 third edition cancels and replaces the second edition (ISO/IEC 21122-5:2022), which has been
technically revised.
The main changes are as follows:
— the reference software has been updated.
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.
© ISO/IEC 2025 – All rights reserved
iv
ISO/IEC/DIS 21122-5:2025(en)
Introduction
This document is part of a series of standards for a low-latency lightweight image coding system, denoted
JPEG XS. It provides the software reference implementation of ISO/IEC 21122-1 and ISO/IEC 21122-2. It
has been successfully compiled and tested on various operating systems at the time of writing. This
reference software implementation includes both encoder and decoder functionality. It is important to
note that this reference software implementation represents just one way of implementing JPEG XS. This
implementation can serve as a validation anchor to other implementations.
No guarantee of the quality that will be achieved by an encoder is provided by its conformance to
ISO/IEC 21122-1 and ISO/IEC 21122-2, as the conformance is only defined in terms of specific
constraints imposed on the syntax of the generated codestream. In particular, while sample encoder
software implementations can suffice to provide some illustrative examples of which quality can be
achieved within the ISO/IEC 21122 series, they provide neither an assurance of minimum guaranteed
image encoding quality nor maximum achievable image encoding quality.
Similarly, the computation resource characteristics in terms of program or data memory usage, execution
speed, etc. of sample software encoder or decoder implementations should not be construed as a
representative of the typical, minimal or maximal computational resource characteristics to be exhibited
by implementations of the ISO/IEC 21122 series.
© ISO/IEC 2025 – All rights reserved
v
DRAFT International Standard ISO/IEC/DIS 21122-5:2025(en)
Information technology — JPEG XS low-latency lightweight image
coding system — Part 5: Reference software
1 Scope
This document contains the reference software of the ISO/IEC 21122 series. It acts as guidance for
implementation of the standardISO/IEC 21122 series and as a reference for conformance testing.
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
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO/IEC 21122-1 and ISO/IEC
21122-2 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/
4 Reference software
4.1 General
In addition to the main text, including Annexes A, B and C, the reference software is available at
https://standards.iso.org/iso-iec/21122/-5/ed-3/en/.
Annex A provides guidelines on how to build the provided reference software.
Annex B describes input and output image file formats that are supported by the provided reference
software.
Annex C provides guidelines on how to use the reference decoder and encoder.
4.2 Purpose
The purpose of this document is to provide the following:
— a reference decoder software implementation, capable of decoding codestreams that conform to
ISO/IEC 21122-1, or to both ISO/IEC 21122-1 and ISO/IEC 21122-2;
© ISO/IEC 2025 – All rights reserved
ISO/IEC/DIS 21122-5:2025(en)
— a sample encoder software implementation, capable of producing codestreams that conform to
ISO/IEC 21122-1, or to both ISO/IEC 21122-1 and ISO/IEC 21122-2.
The use of this reference software is not required for making an implementation of an encoder or decoder
in conformance to any of the parts of the ISO/IEC 21122 series. Requirements established in
ISO/IEC 21122-1 and ISO/IEC 21122-2 shall take precedence over the behaviour of the reference
software.
The reference decoder software generates the normative output of the decoding process specified by
ISO/IEC 21122-1. The output of the reference decoder satisfies the requirements of the strict
conformance point of ISO/IEC 21122-4. It therefore allows conformance testing by means of comparing
the output of a candidate implementation by that of the reference software specified in this document.
Conformance testing is specified in ISO/IEC 21122-4. The reference decoder software can also be used to
validate the syntactic correctness of a codestream by attempting to decode a candidate codestream with
the reference software.
The reference software does not implement the file format functionality of ISO/IEC 21122-3.
4.3 Examples of use
Some examples of use for the reference decoder software implementations are as follows:
— as an illustration of how to perform the decoding processes specified in ISO/IEC 21122-1;
— as the starting basis for the implementation of a decoder that conforms to ISO/IEC 21122-1;
— for testing the conformance of a decoder implementation to ISO/IEC 21122-1 with the procedures
and details on reference testing specified in ISO/IEC 21122-4;
— for (non-exhaustive) testing of the conformance of a codestream (or file) to the const
...
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