ISO/IEC 21122-1:2022
(Main)Information technology — JPEG XS low-latency lightweight image coding system — Part 1: Core coding system
Information technology — JPEG XS low-latency lightweight image coding system — Part 1: Core coding system
This document defines the syntax and an accompanying decompression process that is capable to represent continuous-tone grey-scale, or continuous-tone colour digital images without visual loss at moderate compression rates. Typical compression rates are between 2:1 and 6:1 but can also be higher depending on the nature of the image. In particular, the syntax and the decoding process specified in this document allow lightweight encoder and decoder implementations that limit the end-to-end latency to a fraction of the frame size. However, the definition of transmission channel buffer models necessary to ensure such latency is beyond the scope of this document. This document: — specifies decoding processes for converting compressed image data to reconstructed image data; — specifies a codestream syntax containing information for interpreting the compressed image data; — provides guidance on encoding processes for converting source image data to compressed image data.
Technologies de l'information — Système de codage d'images léger à faible latence JPEG XS — Partie 1: Système de codage de noyau
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Standards Content (Sample)
INTERNATIONAL ISO/IEC
STANDARD 21122-1
Second edition
2022-03
Information technology — JPEG XS
low-latency lightweight image coding
system —
Part 1:
Core coding system
Technologies de l'information — Système de codage d'images léger à
faible latence JPEG XS —
Partie 1: Système de codage de noyau
Reference number
© ISO/IEC 2022
© ISO/IEC 2022
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© ISO/IEC 2022 – All rights reserved
Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions, abbreviated terms and symbols . 1
3.1 Terms and definitions . 1
3.2 Abbreviated terms . 6
3.3 Symbols . 6
4 Conventions . 9
4.1 Conformance language . 9
4.2 Operators . 9
4.2.1 Arithmetic operators . 9
4.2.2 Logical operators . 10
4.2.3 Relational operators . 10
4.2.4 Precedence order of operators . 10
4.2.5 Mathematical functions . 11
5 Functional concepts . .11
5.1 Sample grid, sampling and components . 11
5.2 Interpretation of CFA data .12
5.3 Wavelet decomposition .12
5.4 Codestream. 13
6 Encoder requirements .13
7 Decoder .13
7.1 Decoding process general provisions . 13
7.2 Decoder requirements .15
Annex A (normative) Codestream syntax .16
Annex B (normative) Image data structures .29
Annex C (normative) Entropy decoding .42
Annex D (normative) Quantization .60
Annex E (normative) Discrete wavelet transformation .64
Annex F (normative) Multiple component transformations .74
Annex G (normative) DC level shifting, non-linear transform and output clipping .85
Annex H (informative) Example weight tables .92
Bibliography . 100
iii
© ISO/IEC 2022 – All rights reserved
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).
Attention is drawn to the possibility that some of the elements of this document may be the subject
of patent rights. ISO and IEC shall not be held responsible for identifying any or all such patent
rights. Details of any patent rights identified during the development of the document will be in the
Introduction and/or on the ISO list of patent declarations received (see www.iso.org/patents) or the IEC
list of patent declarations received (see patents.iec.ch).
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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 second edition cancels and replaces the first edition (ISO/IEC 21122-1:2019), which has been
technically revised.
The main changes are as follows:
— coding tools for compressing colour filter array images (CFA images) have been added;
— coding tools that enable lossless coding of images with up to 12 bits per sample have been added;
— support for 4:2:0 sampled images has been 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 www.iso.org/members.html and
www.iec.ch/national-committees.
iv
© ISO/IEC 2022 – All rights reserved
Introduction
The International Organization for Standardization (ISO) and International Electrotechnical
Commission (IEC) draw attention to the fact that it is claimed that compliance with this document may
involve the use of patents.
ISO and IEC take no position concerning the evidence, validity and scope of these patent rights.
The holders of these patent rights have assured ISO and IEC that they are willing to negotiate licences
under reasonable and non-discriminatory terms and conditions with applicants throughout the world.
In this respect, the statements of the holders of these patent rights are registered with ISO and IEC.
Information may be obtained from the patent database available at www.iso.org/patents.
Attention is drawn to the possibility that some of the elements of this document may be the subject
of patent rights other than those in the patent database. ISO and IEC shall not be held responsible for
identifying any or all such patent rights.
v
© ISO/IEC 2022 – All rights reserved
INTERNATIONAL STANDARD ISO/IEC 21122-1:2022(E)
Information technology — JPEG XS low-latency lightweight
image coding system —
Part 1:
Core coding system
1 Scope
This document defines the syntax and an accompanying decompression process that is capable to
represent continuous-tone grey-scale, or continuous-tone colour digital images without visual loss at
moderate compression rates. Typical compression rates are between 2:1 and 6:1 but can also be higher
depending on the nature of the image. In particular, the syntax and the decoding process specified
in this document allow lightweight encoder and decoder implementations that limit the end-to-end
latency to a fraction of the frame size. However, the definition of transmission channel buffer models
necessary to ensure such latency is beyond the scope of this document.
This document:
— specifies decoding processes for converting compressed image data to reconstructed image data;
— specifies a codestream syntax containing information for interpreting the compressed image data;
— provides guidance on encoding processes for converting source image data to compressed image
data.
2 Normative references
There are no normative references in this document.
3 Terms and definitions, abbreviated terms and symbols
3.1 Terms and definitions
For the purposes of this document, the following terms and definitions 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/
3.1.1
band
input data to a specific wavelet filter type (3.1.58) that contributes to the generation of one of the
components (3.1.14) of the image
3.1.2
band type
single number collapsing the information on the component, and horizontal and vertical wavelet
filter types that are applied in the filter cascade reconstructing spatial image samples from inversely
quantized wavelet coefficients
© ISO/IEC 2022 – All rights reserved
3.1.3
bit
binary choice encoded as either 0 or 1
3.1.4
bitplane
array of bits having all the same significance
3.1.5
bitplane count
number of significant bitplanes of a code group, counting from the LSB up to the most significant, non-
empty bitplane
3.1.6
bitplane count subpacket
subset of a packet which decodes to the bitplane counts of all code groups within a packet, followed by
padding and optional filler bytes
Note 1 to entry: See subclause C.5.3.
3.1.7
byte
group of 8 bits
3.1.8
colour filter array
CFA
rectangular array of sensor elements yielding a 1-component picture where the colour to which a sensor
element is sensitive to depends on the position of the sensor element
3.1.9
codestream
compressed image data representation that includes all necessary data to allow a (full or approximate)
reconstruction of the sample values of
...
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