ISO/IEC 21122-2:2024
(Main)Information technology — JPEG XS low-latency lightweight image coding system — Part 2: Profiles and buffer models
Information technology — JPEG XS low-latency lightweight image coding system — Part 2: Profiles and buffer models
This document defines several subsets of the syntax specified in ISO/IEC 21122-1 as profiles. It also defines lower bounds on the throughput in the decoded domain via levels and the encoded domain via sublevels that a conforming decoder implementation shall support. Furthermore, it defines a buffer model to ensure interoperability between implementations in the presence of a latency constraint.
Technologies de l'information — Système de codage d'images léger à faible latence JPEG XS — Partie 2: Profils et modèles tampons
General Information
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Standards Content (Sample)
International
Standard
ISO/IEC 21122-2
Third edition
Information technology — JPEG
2024-08
XS low-latency lightweight image
coding system —
Part 2:
Profiles and buffer models
Technologies de l'information — Système de codage d'images
léger à faible latence JPEG XS —
Partie 2: Profils et modèles tampons
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 Abbreviated terms . 4
5 Symbols . 4
6 Conventions . 7
6.1 Conformance language .7
6.2 Operators .7
6.2.1 Arithmetic operators .7
6.2.2 Logical operators .7
6.2.3 Relational operators .7
6.2.4 Other operators .7
6.2.5 Precedence order of operators .8
6.2.6 Mathematical functions .8
7 Buffer model . 8
7.1 General system block diagram .8
7.2 Influencing variables on the required buffer sizes .9
7.3 Role of the buffer model .10
8 Interpretation of Bayer data . 10
9 Conformance .11
Annex A (normative) Profiles, levels, sublevels and frame buffer bandwidth levels .12
Annex B (normative) Packet-based JPEG XS decoder model .35
Annex C (normative) Packet-based constant bit rate buffer model . 41
Annex D (informative) Encoder model, latency bounds and codestream conformance properties
for the packet-based constant bit rate buffer model . 47
Annex E (informative) JPEG XS latency analysis .52
Bibliography . 61
© 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
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 21122-2:2022), which has been technically
revised. It also incorporates the Amendment ISO/IEC 21122-2:2022/Amd 1:2022.
The main changes compared to the previous edition are:
— addition of conformance points for new profiles;
— addition of the TDC 444.12 and TDC MLS 444.12 profiles for compression of image sequences;
— addition of the CHigh 444.12 profile;
— addition of the MLS.16 profile;
— addition of the frame buffer bandwidth levels and model.
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 2024 – All rights reserved
iv
Introduction
This document is part of a series of standards for a low-latency lightweight image coding system, denoted
as JPEG XS. While ISO/IEC 21122-1 specifies a full set of compression coding tools needed to satisfy all the
requirements of JPEG XS, a targeted application can often work with a simpler and reduced set of coding
tools, and with or without tighter constraints, to meet its targeted goals. For this reason, profiles, levels,
and sublevels are defined in this document. These three concepts facilitate partial and reduced complexity
implementations of ISO/IEC 21122-1 depending on specific application use cases and requirements, while
also safeguarding interoperability.
This document specifies a limited number of profiles to represent interoperability subsets of the codestream
syntax specified in ISO/IEC 21122-1 with each profile serving specific application use cases. In other word,
profiles select a subset of the available coding tools. In addition, levels and sublevels provide limits to the
maximum throughput in respectively the decoded (spatial/pixel) and the encoded (codestream) domains. In
this way, profiles, levels and sublevels allow designing cost-efficient implementations that serve the needs of
the desired applications.
A major requirement of JPEG XS is to allow low end-to-end latency, limited to a fraction of the frame size. To
ensure this low-latency property, this document also specifies a buffer model, consisting of a decoder model
and a transmission channel model. The models show the interaction of a hypothetical reference decoder,
including its smoothing buffer with a constant bitrate channel feeding this buffer. The size of the decoder
smoothing buffer is computed from the profile, level, and sublevel. Codestreams are formed such that the
buffer of a decoder, operating according to this buffer model, never overflows or underflows. In effect,
the buffer model provides encoders with the necessary information to generate codestreams that can be
decoded by an arbitrary decoder implementation, ensuring system interoperability.
In addition to the size of the decoder smoothing buffer, end-to-end latency also depends on the latency inherent
to each processing step of the encoding-decoding chain whose methods are described in ISO/IEC 21122-1.
To help implementers estimate the latency of their device, this document gives extra information on the
minimum latency that can be achieved by the different methods described in ISO/IEC 21122-1.
© ISO/IEC 2024 – All rights reserved
v
International Standard ISO/IEC 21122-2:2024(en)
Information technology — JPEG XS low-latency lightweight
image coding system —
Part 2:
Profiles and buffer models
1 Scope
This document defines several subsets of the syntax specified in ISO/IEC 21122-1 as profiles. It also defines
lower bounds on the throughput in the decoded domain via levels and the encoded domain via sublevels
that a conforming decoder implementation shall support. Furthermore, it defines a buffer model to ensure
interoperability between implementations in the presence of a latency constraint.
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
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO/IEC 21122-1 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
blanking codestream fragment
placeholder codestream fragment representing blanking periods
3.2
buffer model
combination of a decoder model (3.8) and a channel model (3.4) whose behaviour can be defined by a set of
parameters
3.3
buffer model instance
specific configuration of a buffer model (3.2) specified by the assignment of well-defined values to the buffer
...
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