ISO/IEC 21122-4:2025
(Main)Information technology — JPEG XS low-latency lightweight image coding system — Part 4: Conformance testing
Information technology — JPEG XS low-latency lightweight image coding system — Part 4: Conformance testing
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.
Technologies de l'information — Système de codage d'images léger à faible latence JPEG XS — Partie 4: Essais de conformité
General Information
Relations
Standards Content (Sample)
International
Standard
ISO/IEC 21122-4
Third edition
Information technology — JPEG
2025-04
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 2025
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© ISO/IEC 2025 – All rights reserved
ii
Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Abbreviated terms . 2
5 General description . 2
5.1 Overview .2
5.2 Codestream syntax testing.2
5.3 Test procedures to test decoders for conformance to ISO/IEC 21122-1 .2
5.4 Test procedures to test decoders for conformance to ISO/IEC 21122-3 .3
5.5 File format syntax testing .3
5.6 ISO/IEC 21122-2 Profile, level, sublevel and frame buffer level conformance testing .3
5.7 ISO/IEC 21122-2 Buffer model conformance testing .3
5.8 ISO/IEC 21122-2 Frame buffer model conformance testing .3
5.9 Electronic attachments .3
6 Conformance files availability and updates . 3
Annex A (normative) Codestream syntax testing procedures . 4
Annex B (normative) Decoder testing procedures. 5
Annex C (normative) Decoder conformance tests .11
Annex D (normative) File format syntax testing procedures . 17
Annex E (normative) Buffer model conformance testing .18
Annex F (normative) Buffer model conformance testing .20
Annex G (informative) Attached software .22
Bibliography .24
© ISO/IEC 2025 – All rights reserved
iii
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 21122-4:2022), which has been technically
revised.
The main changes are as follows:
— reference test streams have been revised;
— a test protocol for testing sequences of codestreams was added;
— additional test streams for the TDC 444.12 and TDC MLS 444.12 profiles were added;
— a test protocol for testing the frame buffer bandwidth model was added.
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 https://www.iso.org/members.html and
https://www.iec.ch/national-committees.
© ISO/IEC 2025 – All rights reserved
iv
Introduction
This document is part of a series of standards for a low-latency lightweight image coding system, denoted
JPEG XS. It provides the conformance testing procedures for ISO/IEC 21122-1, ISO/IEC 21122-2 and
ISO/IEC 21122-3.
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, sublevel, frame
buffer level 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, sublevel and frame buffer level;
— codestreams, decoded images, and error metrics to be used within the decoder testing procedures;
— a buffer model test;
— abstract test suites.
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
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.
© ISO/IEC 2025 – All rights reserved
v
International Standard ISO/IEC 21122-4:2025(en)
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.
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
codestream sequence
contiguously enumerated set of codestreams representing a temporally consistent video signal
3.2
executable test suite
set of executable test cases in the form of codestreams that are input into an implementation under test
3.3
interlace
scan method scanning each frame as two fields consisting of the even and odd lines of the frame
© ISO/IEC 2025 – All rights reserved
3.4
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.
3.5
procedure
set of steps which accomplishes one of the tasks which comprise an encoding or decoding process
3.6
progressive
scan method scanning each frame as a single scan, including both the even and odd lines
3.7
test codestream set
(sub-)set
...
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