ISO/IEC 6048-4:2026

• Abstract:

  This document specifies the framework, concepts, methodology for testing, and criteria to be achieved to claim conformance to the image coding technology Rec. ITU-T T.840.1 | ISO/IEC 6048-1, known as Learning-based image coding (JPEG AI). It lists the conformance testing procedures.

• Status: Published
• Publication Date: 20-Sep-2026
• ICS: 35.040.30 - Coding of graphical and photographical information
• Technical Committee: ISO/IEC JTC 1/SC 29 - Coding of audio, picture, multimedia and hypermedia information
• Drafting Committee: ISO/IEC JTC 1/SC 29 - Coding of audio, picture, multimedia and hypermedia information
• Current Stage: 6060 - International Standard published
• Start Date: 21-Sep-2026
• Due Date: 24-Jul-2026
• Completion Date: 21-Sep-2026

International
Standard
ISO/IEC 6048-4
First edition
Information technology — JPEG
2026-09
AI learning-based image coding
system —
Part 4:
Conformance
Reference number
© ISO/IEC 2026
All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may
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© ISO/IEC 2026 – All rights reserved
ii
Foreword
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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 ITU-T (as ITU-T T.840.4) and drafted in accordance with its editorial rules, in
collaboration with Joint Technical Committee ISO/IEC JTC 1, Information technology, Subcommittee SC 29,
Coding of audio, picture, multimedia and hypermedia information.
A list of all parts in the ISO/IEC 6048 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 2026 – All rights reserved
iii
CONTENTS
Page
1 Scope . 1
2 Normative references . 1
2.1 Identical Recommendations | International Standards . 1
2.2 Paired Recommendations | International Standards equivalent in technical content . 1
2.3 Additional references . 1
3 Definitions . 1
4 Abbreviations . 1
5 Conventions . 2
5.1 General . 2
5.2 Arithmetic operators . 2
6 General description . 2
6.1 Overview . 2
6.2 Electronic attachment . 2
6.3 Conformance files availability and updates . 2
7 Decoder testing procedures . 3
7.1 General . 3
7.2 Decoder test procedure . 4
7.3 Test procedures for a TCS element . 4
7.4 Files for testing . 5
7.5 Decoder settings . 5
7.6 Output file format conversion . 5
7.7 Sample format conversion . 5
7.8 Reference components file format (PGX) . 6
7.9 Comparison of the decoded image components with the original image components . 6
7.10 Comparison of the decoded latent space tensor with the reference latent space tensor . 7
8 Decoder conformance tests . 7
8.1 General . 7
8.2 Reference codestreams for the Main@Simple profile . 7
8.3 Reference codestreams for the Main@Base profile . 8
8.4 Reference codestreams for the Main@High profile . 8
9 Attached software (informative) . 9
9.1 List of attachments . 9
9.2 Installation of Python scripts . 9
Rec. ITU-T T.840.4 (06/2026)
© ISO/IEC 2026 – All rights reserved
iv
INTERNATIONAL STANDARD
ITU-T RECOMMENDATION
Information technology – JPEG AI learning-based image coding system: Conformance
1 Scope
This Recommendation | International Standard specifies the framework, concepts, methodology for testing, and criteria
to be achieved to claim conformance to the image coding technology Rec. ITU-T T.840.1 | ISO/IEC 6048-1, known as
Learning-based image coding (JPEG AI). It lists the conformance testing procedures.
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
– Rec. ITU-T T.840.1 (2025) | ISO/IEC 6048-1:2025 – Information technology – JPEG AI learning-based
image coding: Core coding system.
– Rec. ITU-T T.840.2 (2026) | ISO/IEC 6048-2:2026 – Information technology – JPEG AI learning-based
image coding: Profiling.
– Rec. ITU-T T.840.5 (2026) | ISO/IEC 6048-5:2026 – Information technology – JPEG AI learning-based
image coding: File format.
2.2 Paired Recommendations | International Standards equivalent in technical content
– None.
2.3 Additional references
– None.
3 Definitions
In addition to the terms defined in Rec. ITU-T T.840.1 | ISO/IEC 6048-1, the following definitions apply:
3.1 executable test suite: Set of executable test cases in the form of codestreams that are input into an
implementation under a test.
3.2 JPEG AI file: Sequence of bytes encoding an image in the JAI file format specified in Rec. ITU-T T.840.5 |
ISO/IEC 6048-5.
3.3 procedure: Set of steps which accomplishes one of the tasks which comprise 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 Abbreviations
In addition to abbreviations in Rec. ITU-T T.840.1 | ISO/IEC 6048-1, the following abbreviations apply:
IUT Implementation Under Test
MSE Mean Squared Error
PSNR Peak Signal to Noise Ratio
Rec. ITU-T T.840.4 (06/2026)
© ISO/IEC 2026 – All rights reserved
TCS Test Codestream Set
5 Conventions
5.1 General
The term "this Specification" is used to refer to this Recommendation | International Standard.
The word "shall" is used to express mandatory requirements for conformance to this Specification. When used to express
a mandatory constraint on the values of syntax elements or the values of variables derived from these syntax elements, it
is the responsibility of the encoder to ensure that the constraint is fulfilled.
The word "may" is used to refer to behaviour that is allowed, but not necessarily required.
The word "should" is used to refer to behaviour of an implementation that is encouraged to be followed under anticipated
ordinary circumstances, but is not a mandatory requirement for conformance to this Specification.
The content of this Specification that is identified as "informative" does not establish any mandatory requirements for
conformance to this Specification and is thus not considered an integral part of this Specification. Informative remarks in
the text are, in some cases, set apart and prefixed with the word "note" or "NOTE".
NOTE – The mathematical operators used in this Specification are similar to those used in the C programming language. However,
the results of integer division and arithmetic shift operations are defined more precisely, and additional operations are defined, such
as exponentiation and real-valued division. Numbering and counting conventions generally begin from 0, e.g., "the first" is
equivalent to the 0-th, "the second" is equivalent to the 1-th, etc.
5.2 Arithmetic operators
All arithmetic operators are identical to those defined in Rec. ITU-T T.840.1 | ISO/IEC 6048-1.
6 General description
6.1 Overview
The Rec. ITU-T T.840 | ISO/IEC 6048 series, also known as JPEG AI, consists of multiple Recommendations |
International Standards. Rec. ITU-T T.840.1 | ISO/IEC 6048-1 specifies the core coding system and the syntax of a
codestream. Rec. ITU-T T.840.2 | ISO/IEC 6048-2 specifies profiles, and Rec. ITU-T T.840.5 | ISO/IEC 6048-5 specifies
a file container format. This Specification defines test suites for decoder conformance tests for Rec. ITU-T T.840.1 |
ISO/IEC 6048-1 and Rec. ITU-T T.840.2 | ISO/IEC 6048-2.
6.2 Electronic attachment
In addition to the specification text, an electronic attachment is provided at https://standards.iso.org/iso-iec/6048/-4/ed-
1/en/ and https://www.itu.int/myworkspace/t-signals/vectors?val=44 in compressed form. This compressed files are
referred to as the electronic attachment from here on. The archive comprises two folders: conformance_data and
conformance_testing_sw. All the data needed for conformance testing, including codestreams, original images, reference
latent space tensors, residual MD5 hashes and test description files are located in the folder conformance_data. The
auxiliary software designed to facilitate testing is located in the folder conformance_testing_sw. This Specification
contains instructions for the use of the attached files and software.
6.3 Conformance files availability and updates
The conformance test images, streams and conformance test software released with this Specification are the latest tested
versions available at the date at which this Specification was published.
Rec. ITU-T T.840.4 (06/2026)
© ISO/IEC 2026 – All rights reserved
7 Decoder testing procedures
7.1 General
This clause defines procedures for determining whether a JPEG AI decoder implementation is conforming to a particular
profile.
Two conformance types are defined:
– conformance type A (low tolerance), and
– conformance type B (moderate tolerance).
Conformance testing for one test codestream set (TCS) element comprises testing of three conformance points: decoded
residual tensor, decoded latent space tensor (feature space) and the decoded image. The location of these conformance
points in the JPEG AI decoding scheme is depicted in Figure 7-1. Residual tensor conformance is measured after the
entropy decoder, more specifically after the residual data decoding process (clause 12.4.3 of Rec. ITU-T T.840.1 |
ISO/IEC 6048-1). Output tensors 𝑟̂0 and 𝑟̂1 of this process are used for luma and chroma correspondingly. Latent
space tensor conformance is measured after the latent tensor reconstruction (clause 14.3.1 of Rec. ITU-T T.840.1 |
ISO/IEC 6048-1), more specifically, output tensors x[0], x[1] of the process 14.3.1 are used for luma and chroma
correspondingly. The decoded image conformance is measured after the conversion to the output picture format (clause
9.7 of Rec. ITU-T T.840.1 | ISO/IEC 6048-1).
Figure 7-1 – Conformance points location
The residual tensor produced by an implementation under test (IUT) should be exactly the same as the reference residual
tensor (this is called "strict conformance" in Figure 7-1 under "Residual tensor"). Latent space tensor produced by IUT
can have a minor deviation from the reference latent space tensor (this is called "soft conformance" in Figure 7-1 under
"Latent space tensor"). Decoded image produced by IUT can also have a minor deviation from the reference decoded
image (this is called "soft conformance" in Figure 7-1 under "Decoded image"). For the decoded image two conformance
types are defined: A and B. Type A conformance corresponds to smaller tolerance intervals, whereas for Type B
conformance tolerance intervals are bigger.
NOTE – Tolerance intervals for Type A conformance correspond to the difference between inference of the same 32-bit floating
point model on two different graphics processing units. Tolerance intervals for Type B conformance correspond to the difference
between inference of the floating-point and quantized models.
In the case of both conformance types (A and B), the decoded image can be better (closer to the original) than the reference
decoded image, but should not be noticeably worse.
The general conformance testing procedure is described in clause 7.2. The detailed algorithm of the conformance testing
for one TCS element is described in clause 7.3. Tolerance intervals for each test are presented in clauses 8.2 – 8.4.
The conformance bitstreams have values of decoder_profile_id and level_idc corresponding to a set of specified
constraints on a bitstream described in Rec. ITU-T T.840.2 | ISO/IEC 6048-2. The bitstreams for profiles Main@Simple,
Main@Base and Main@High are described in Tables 1, 2 and 3 of clauses 8.2, 8.3 and 8.4 correspondingly. The level of
each conformance bitstream is specified in the "Level" column.
Rec. ITU-T T.840.4 (06/2026)
© ISO/IEC 2026 – All rights reserved
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