ISO/IEC 21122-3:2024

International
Standard
ISO/IEC 21122-3
Third edition
Information technology — JPEG
2024-08
XS low-latency lightweight image
coding system —
Part 3:
Transport and container formats
Reference number
© ISO/IEC 2024
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© ISO/IEC 2024 – All rights reserved
ii
Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Symbols and abbreviated terms. 3
4.1 Symbols .3
4.2 Abbreviated terms .3
4.3 Naming conventions for numerical values .3
5 Conformance . 4
6 Colour specification . 4
7 Organization of the document . 4
Annex A (normative) Syntax elements for JPEG XS compressed content . 5
Annex B (normative) Use of JPEG XS codestreams in still image file format - JXS .31
Annex C (normative) Use of JPEG XS codestreams in the ISOBMFF - Motion JPEG XS.36
Annex D (normative) Use of JPEG XS codestreams in the HEIF image file format .40
Annex E (normative) Use of JPEG XS codestreams outside of file formats . 47
Bibliography .49

© ISO/IEC 2024 – 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
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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 21122-3:2022), which has been
technically revised.
The main changes are as follows:
— support for JPEG XS codestreams using temporal differential coding (TDC).
— clarifications on coding of interlaced signals.
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 2024 – 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.
In many use cases during production or transmission of a movie, limiting the latency and the recompression
loss is a more important aspect than the compression efficiency. The JPEG XS coding system offers
compression and recompression of image sequences with very moderate computational resources while
remaining robust under multiple compression and decompression cycles and mixing of content sources, e.g.
embedding of subtitles, overlays or logos. Typical target compression ratios ensuring visually lossless quality
are in the range of 2:1 to 20:1, depending on the nature of the source material. The end-to-end latency can
be confined to a fraction of a frame, typically between a small number of lines down to below a single line.
This document specifies transport and container formats for JPEG XS codestreams. It also defines metadata
that enriches transport protocols for transmission of image sequences, in order to facilitate transport,
editing and presentation.
© ISO/IEC 2024 – All rights reserved
v
International Standard ISO/IEC 21122-3:2024(en)
Information technology — JPEG XS low-latency lightweight
image coding system —
Part 3:
Transport and container formats
1 Scope
This document defines transport and container formats for JPEG XS codestreams as specified in
ISO/IEC 21122-1. It defines file formats for working with still image and motion image sequence files on
computer platforms and gives guidance on how to embed the codestream in transport streams, allowing
internet-based communication.
This document uses already existing specifications for file formats and extends them for the embedding of
JPEG XS codestreams.
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 15076-1, Image technology colour management — Architecture, profile format and data structure — Part
1: Based on ICC.1:2010
ISO/IEC 646, Information technology — ISO 7-bit coded character set for information interchange
ISO/IEC 10646, Information technology — Universal coded character set (UCS)
ISO/IEC 11578, Information technology — Open Systems Interconnection — Remote Procedure Call (RPC)
ISO/IEC 14496-12, Coding of audio-visual objects — Part 12: ISO base media file format
ISO/IEC 21122-1, JPEG XS low-latency lightweight image coding system — Part 1: Core coding system
ISO/IEC 21122-2, JPEG XS low-latency lightweight image coding system — Part 2: Profiles and buffer models
ISO/IEC 23008-12:2022, Information technology — High efficiency coding and media delivery in heterogeneous
environments — Part 12: Image File Format
ISO/CIE 11664-1, Colorimetry — Part 1: CIE standard colorimetric observers
Rec. ITU-T H.273 | ISO/IEC 23091-2, Coding-independent code points — Part 2: Video
ANSI/CTA 861-G:2016, A DTV Profile for Uncompressed High Speed Digital Interfaces
W3C Recommendation, Extensible Markup Language (XML) 1.0 (Fifth Edition), 26 Nov. 2008 (https:// www
.w3 .org/ TR/ REC -xml/ )
3 Terms and definitions
For the purposes of this document the terms and definitions given in ISO/IEC 14496-12, ISO/IEC 21122-1,
ISO/IEC 21122-2, ISO/IEC 23008-12 and the following apply.

© ISO/IEC 2024 – All rights reserved
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
aux
auxiliary component channel typically used as opacity channel or alpha mask
3.2
big-endian
byte ordering from the most significant to the least significant byte of multi-byte value representations
3.3
box
structured collection of data describing the image or the image decoding process
3.4
box content
data wrapped within the box (3.3) structure
3.5
box type
kind of information stored with the box (3.3)
3.6
byte
group of 8 bits
3.7
coding-independent code point
code point based on enumerated values for the definition of the colourspaces
Note 1 to entry: Code points defined in Rec. ITU-T H.273 | ISO/IEC 23091-2.
3.8
high efficiency image file format
image file format which can embed still images and motion sequences (3.11)
Note 1 to entry: Based on ISO/IEC 23008-12.
3.9
image collection
unordered set of images without an implied or signalled presentation order or presentation time stamps
3.10
JXS
still image file format with JPEG XS compressed images
3.11
motion sequence
movie
timed sequence (3.15) of images
3.12
sample
single element in the two-dimensional image array which comprises a component
Note 1 to entry: This definition is used in Annex A.

© ISO/IEC 2024 – All rights reserved
3.13
sample
all the data associated with a single time
Note 1 to entry: This definition is used in Annexes B and C as data associated with one coded image in a sequence.
3.14
superbox
box (3.3) that carries other boxes as payload data
3.15
timed sequence
linearly ordered sequence of media entities such as images where each entity is presented at a well defined
time stamp
4 Symbols and abbreviated terms
4.1 Symbols
N number of components in an image as defined in ISO/IEC 21122-1
c
P Level, sublevel and frame-buffer level (if applicable) a particular codestream
lev
conforms to as defined in ISO/IEC 21122-2
P profile a particular codestream conforms to as defined in ISO/IEC 21122-2
pih
Picture()
JPEG XS codestream as defined in ISO/IEC 21122-1
Codestream_Header()
codestream header preceding the image data in the codestream without any
tpc_marker() as defined in subclause A.5.5
Codestream_Body()
coded image data in the codestream including any tpc_marker() if such a marker
is present, without Codestream_Header() as defined in subclause A.5.5
4.2 Abbreviated terms
For the purposes of this document the abbreviated terms given in ISO/IEC 14496-12, ISO/IEC 21122-1,
ISO/IEC 21122-2, ISO/IEC 23008-12 and the following apply.
CICP coding-independent code points
CIE Commision Internationale de l’Eclairage
HEIF high efficiency image file format
ISOBMFF iso base media file format
LSB least significant bit
MSB most significant bit
UTF-8 8-bit Unicode transformation format as defined in ISO/IEC 10646
4.3 Naming conventions for numerical values
Integer numbers are expressed as bit patterns, hexadecimal values, or decimal numbers. Bit patterns and
hexadecimal values have both a numerical value and an associated particular length in bits.

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