ISO/IEC 18477-8:2020
(Main)Information technology — Scalable compression and coding of continuous-tone still images — Part 8: Lossless and near-lossless coding
Information technology — Scalable compression and coding of continuous-tone still images — Part 8: Lossless and near-lossless coding
This document specifies a coding format, referred to as JPEG XT, which is designed primarily for continuous-tone photographic content. This document defines extensions that allow lossless coding of such content while staying compatible with the core coding system specified in ISO/IEC 18477-1.
Technologies de l'information — Compression échelonnable et codage d'images plates en ton continu — Partie 8: Codage sans perte et quasi sans perte
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FINAL
INTERNATIONAL ISO/IEC
DRAFT
STANDARD FDIS
18477-8
ISO/IEC JTC 1/SC 29
Information technology — Scalable
Secretariat: JISC
compression and coding of
Voting begins on:
2020-03-13 continuous-tone still images —
Voting terminates on:
Part 8:
2020-05-08
Lossless and near-lossless coding
RECIPIENTS OF THIS DRAFT ARE INVITED TO
SUBMIT, WITH THEIR COMMENTS, NOTIFICATION
OF ANY RELEVANT PATENT RIGHTS OF WHICH
THEY ARE AWARE AND TO PROVIDE SUPPOR TING
DOCUMENTATION.
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Reference number
BEING ACCEPTABLE FOR INDUSTRIAL, TECHNO-
ISO/IEC FDIS 18477-8:2020(E)
LOGICAL, COMMERCIAL AND USER PURPOSES,
DRAFT INTERNATIONAL STANDARDS MAY ON
OCCASION HAVE TO BE CONSIDERED IN THE
LIGHT OF THEIR POTENTIAL TO BECOME STAN-
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©
NATIONAL REGULATIONS. ISO/IEC 2020
ISO/IEC FDIS 18477-8:2020(E)
© ISO/IEC 2020
All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may
be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting
on the internet or an intranet, without prior written permission. Permission can be requested from either ISO at the address
below or ISO’s member body in the country of the requester.
ISO copyright office
CP 401 • Ch. de Blandonnet 8
CH-1214 Vernier, Geneva
Phone: +41 22 749 01 11
Fax: +41 22 749 09 47
Email: copyright@iso.org
Website: www.iso.org
Published in Switzerland
ii © ISO/IEC 2020 – All rights reserved
ISO/IEC FDIS 18477-8:2020(E)
Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms, definitions, symbols and abbreviated terms . 1
3.1 Terms and definitions . 1
3.2 Symbols . 5
3.3 Abbreviated terms . 6
4 Conventions . 6
4.1 Conformance language . 6
4.2 Operators . 6
4.2.1 Arithmetic operators . 6
4.2.2 Logical operators . 7
4.2.3 Relational operators . 7
4.2.4 Precedence order of operators . 7
4.2.5 Mathematical functions . 7
5 General . 8
5.1 General definitions . 8
5.2 Overview of this document . 8
5.3 Profiles .10
5.4 Encoder requirements .10
5.5 Decoder requirements.10
Annex A (normative) Encoding and decoding process .12
Annex B (normative) Boxes .17
Annex C (normative) Multi-component decorrelation transformation .25
Annex D (normative) Entropy coding of residual data in the DCT-bypass and large range mode .28
Annex E (normative) Discrete cosine transformation .39
Annex F (normative) Component upsampling .52
Annex G (normative) Quantization and noise shaping for the DCT-bypass process .54
Annex H (normative) Profiles .57
Bibliography .58
© ISO/IEC 2020 – All rights reserved iii
ISO/IEC FDIS 18477-8:2020(E)
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).
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 http:// patents .iec .ch).
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.
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 18477-8:2016), which has been
technically revised.
The main changes compared to the previous edition are as follows:
— Annex F.2 has been revised to adopt centred upsampling by default;
— minor editorial changes throughout.
A list of all parts in the ISO/IEC 18477 series can be found on the ISO website.
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.
iv © ISO/IEC 2020 – All rights reserved
ISO/IEC FDIS 18477-8:2020(E)
Introduction
This document specifies a coded codestream format for storage of continuous-tone high and low
dynamic range photographic content. This is a scalable lossy to lossless image coding system supporting
multiple component images consisting of integer samples between 8- and 16-bit resolution, or floating
point samples of 16-bit resolution. It is by itself an extension of ISO/IEC 18477-6 and ISO/IEC 18477-7,
which specify intermediate range and high-dynamic range image decoding algorithms. Both of these
are based on the box-based file format specified in ISO/IEC 18477-3, which is again an extension of
ISO/IEC 18477-1; the codestream is composed in such a way that legacy applications conforming to
Rec. ITU-T T.81 | ISO/IEC 10918-1 are able to reconstruct a lossy, low dynamic range, 8 bits per sample
version of the image.
Today, the most widely used digital photography format, a minimal implementation of JPEG (specified
in Rec. ITU-T T.81 | ISO/IEC 10918-1), uses a bit depth of 8; each of the three channels that together
compose an image pixel is represented by 8 bits, providing 256 representable values per channel.
For more demanding applications, it is not uncommon to use a bit depth of 16, providing 65 536
representable values to describe each channel within a pixel, resulting in over 2.8×10 representable
colour values. In some less common scenarios, even greater bit depths are used, requiring a floating-
point sample representation.
Most common photo and image formats use an 8-bit or 16-bit unsigned integer value to represent some
function of the intensity of each colour channel. While it might be theoretically possible to agree on
one method for assigning specific numerical values to real world colours, doing so is not practical.
Since any specific device has its own limited range for colour reproduction, the device’s range may be a
small portion of the agreed-upon universal colour range. As a result, such an approach is an extremely
inefficient use of the available numerical values, especially when using only 8 bits (or 256 unique
values) per channel. To represent pixel values as efficiently as possible, devices use a numeric encoding
optimized for their own range of possible colours or gamut.
This document is primarily designed to encode intermediate or high dynamic image sample values
without loss, or with a precisely controllable bounded loss using the tools defined in ISO/IEC 18477-1
and some minimal extensions of those tools. The goal is to provide a backwards-compatible coding
specification that allows legacy applications and existing toolchains to continue to operate on
codestreams conforming to this document.
JPEG XT has been designed to be backwards compatible to legacy applications while at the same time
having a small coding complexity; JPEG XT uses, whenever possible, functional blocks of Rec. ITU-T T.81
| ISO/IEC 10918-1 to extend the functionality of the legacy JPEG coding system. It is optimized for
storage and transmission of intermediate and high dynamic range and wide colour gamut 8- to 16-
bit integer or 16-bit floating point images while also enabling low-complexity encoder and decoder
implementations.
This document is an extension of ISO/IEC 18477-1, a compression system for continuous tone digital
still images which is backwards compatible with Rec. ITU-T T.81 | ISO/IEC 10918-1. That is, legacy
applications conforming to Rec. ITU-T T.81 | ISO/IEC 10918-1 will be able to reconstruct streams
generated by an encoder conforming to this document, though will possibly not be able to reconstruct
such streams in full dynamic range, full quality or without loss.
This document is itself based on ISO/IEC 18477-3 that defines a box-based file format similar to
other JPEG standards. It also contains elements of ISO/IEC 18477-6 and ISO/IEC 18477-7. The aim
of this document is to provide a migration path for legacy applications to support lossless coding of
intermediate and high dynamic range images, that is images that are either represented by sample
values requiring 8- to 16-bit precision, or even using 16-bit floating point sample resolution. While Rec.
ITU-T T.81 | ISO/IEC 10918-1 already defines a lossless mode for integer samples, images encoded in
this mode cannot be decoded by applications only supporting
...
INTERNATIONAL ISO/IEC
STANDARD 18477-8
Second edition
2020-05
Information technology — Scalable
compression and coding of
continuous-tone still images —
Part 8:
Lossless and near-lossless coding
Technologies de l'information — Compression échelonnable et codage
d'images plates en ton continu —
Partie 8: Codage sans perte et quasi sans perte
Reference number
©
ISO/IEC 2020
© ISO/IEC 2020
All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may
be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting
on the internet or an intranet, without prior written permission. Permission can be requested from either ISO at the address
below or ISO’s member body in the country of the requester.
ISO copyright office
CP 401 • Ch. de Blandonnet 8
CH-1214 Vernier, Geneva
Phone: +41 22 749 01 11
Fax: +41 22 749 09 47
Email: copyright@iso.org
Website: www.iso.org
Published in Switzerland
ii © ISO/IEC 2020 – All rights reserved
Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms, definitions, symbols and abbreviated terms . 1
3.1 Terms and definitions . 1
3.2 Symbols . 5
3.3 Abbreviated terms . 6
4 Conventions . 6
4.1 Conformance language . 6
4.2 Operators . 6
4.2.1 Arithmetic operators . 6
4.2.2 Logical operators . 7
4.2.3 Relational operators . 7
4.2.4 Precedence order of operators . 7
4.2.5 Mathematical functions . 7
5 General . 8
5.1 General definitions . 8
5.2 Overview of this document . 8
5.3 Profiles .10
5.4 Encoder requirements .10
5.5 Decoder requirements.10
Annex A (normative) Encoding and decoding process .12
Annex B (normative) Boxes .17
Annex C (normative) Multi-component decorrelation transformation .25
Annex D (normative) Entropy coding of residual data in the DCT-bypass and large range mode .28
Annex E (normative) Discrete cosine transformation .39
Annex F (normative) Component upsampling .52
Annex G (normative) Quantization and noise shaping for the DCT-bypass process .54
Annex H (normative) Profiles .57
Bibliography .58
© ISO/IEC 2020 – 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).
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 http:// patents .iec .ch).
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.
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 18477-8:2016), which has been
technically revised.
The main changes compared to the previous edition are as follows:
— Annex F.2 has been revised to adopt centred upsampling by default;
— minor editorial changes throughout.
A list of all parts in the ISO/IEC 18477 series can be found on the ISO website.
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.
iv © ISO/IEC 2020 – All rights reserved
Introduction
This document specifies a coded codestream format for storage of continuous-tone high and low
dynamic range photographic content. This is a scalable lossy to lossless image coding system supporting
multiple component images consisting of integer samples between 8- and 16-bit resolution, or floating
point samples of 16-bit resolution. It is by itself an extension of ISO/IEC 18477-6 and ISO/IEC 18477-7,
which specify intermediate range and high-dynamic range image decoding algorithms. Both of these
are based on the box-based file format specified in ISO/IEC 18477-3, which is again an extension of
ISO/IEC 18477-1; the codestream is composed in such a way that legacy applications conforming to
Rec. ITU-T T.81 | ISO/IEC 10918-1 are able to reconstruct a lossy, low dynamic range, 8 bits per sample
version of the image.
Today, the most widely used digital photography format, a minimal implementation of JPEG (specified
in Rec. ITU-T T.81 | ISO/IEC 10918-1), uses a bit depth of 8; each of the three channels that together
compose an image pixel is represented by 8 bits, providing 256 representable values per channel.
For more demanding applications, it is not uncommon to use a bit depth of 16, providing 65 536
representable values to describe each channel within a pixel, resulting in over 2.8×10 representable
colour values. In some less common scenarios, even greater bit depths are used, requiring a floating-
point sample representation.
Most common photo and image formats use an 8-bit or 16-bit unsigned integer value to represent some
function of the intensity of each colour channel. While it might be theoretically possible to agree on
one method for assigning specific numerical values to real world colours, doing so is not practical.
Since any specific device has its own limited range for colour reproduction, the device’s range may be a
small portion of the agreed-upon universal colour range. As a result, such an approach is an extremely
inefficient use of the available numerical values, especially when using only 8 bits (or 256 unique
values) per channel. To represent pixel values as efficiently as possible, devices use a numeric encoding
optimized for their own range of possible colours or gamut.
This document is primarily designed to encode intermediate or high dynamic image sample values
without loss, or with a precisely controllable bounded loss using the tools defined in ISO/IEC 18477-1
and some minimal extensions of those tools. The goal is to provide a backwards-compatible coding
specification that allows legacy applications and existing toolchains to continue to operate on
codestreams conforming to this document.
JPEG XT has been designed to be backwards compatible to legacy applications while at the same time
having a small coding complexity; JPEG XT uses, whenever possible, functional blocks of Rec. ITU-T T.81
| ISO/IEC 10918-1 to extend the functionality of the legacy JPEG coding system. It is optimized for
storage and transmission of intermediate and high dynamic range and wide colour gamut 8- to 16-
bit integer or 16-bit floating point images while also enabling low-complexity encoder and decoder
implementations.
This document is an extension of ISO/IEC 18477-1, a compression system for continuous tone digital
still images which is backwards compatible with Rec. ITU-T T.81 | ISO/IEC 10918-1. That is, legacy
applications conforming to Rec. ITU-T T.81 | ISO/IEC 10918-1 will be able to reconstruct streams
generated by an encoder conforming to this document, though will possibly not be able to reconstruct
such streams in full dynamic range, full quality or without loss.
This document is itself based on ISO/IEC 18477-3 that defines a box-based file format similar to
other JPEG standards. It also contains elements of ISO/IEC 18477-6 and ISO/IEC 18477-7. The aim
of this document is to provide a migration path for legacy applications to support lossless coding of
intermediate and high dynamic range images, that is images that are either represented by sample
values requiring 8- to 16-bit precision, or even using 16-bit floating point sample resolution. While Rec.
ITU-T T.81 | ISO/IEC 10918-1 already defines a lossless mode for integer samples, images encoded in
this mode cannot be decoded by applications only supporting the lossy 8-bit-mode; the coding engine
for lossless coding in Rec. ITU-T T.81 | ISO/IEC 10918-1 is completely different from the lossy coding
mode. Unlike the legacy standard, this document defines a lossless scalable coding engine supporting
all bit depths between 8 and 16 bits per sample, including 16-bit floating point samples, while also
staying compatible with legacy applications. Such applications will continue to work, but will only ab
...
INTERNATIONAL ISO/IEC
STANDARD 18477-8
Second edition
2020-05
Information technology — Scalable
compression and coding of
continuous-tone still images —
Part 8:
Lossless and near-lossless coding
Technologies de l'information — Compression échelonnable et codage
d'images plates en ton continu —
Partie 8: Codage sans perte et quasi sans perte
Reference number
©
ISO/IEC 2020
© ISO/IEC 2020
All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may
be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting
on the internet or an intranet, without prior written permission. Permission can be requested from either ISO at the address
below or ISO’s member body in the country of the requester.
ISO copyright office
CP 401 • Ch. de Blandonnet 8
CH-1214 Vernier, Geneva
Phone: +41 22 749 01 11
Fax: +41 22 749 09 47
Email: copyright@iso.org
Website: www.iso.org
Published in Switzerland
ii © ISO/IEC 2020 – All rights reserved
Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms, definitions, symbols and abbreviated terms . 1
3.1 Terms and definitions . 1
3.2 Symbols . 5
3.3 Abbreviated terms . 6
4 Conventions . 6
4.1 Conformance language . 6
4.2 Operators . 6
4.2.1 Arithmetic operators . 6
4.2.2 Logical operators . 7
4.2.3 Relational operators . 7
4.2.4 Precedence order of operators . 7
4.2.5 Mathematical functions . 7
5 General . 8
5.1 General definitions . 8
5.2 Overview of this document . 8
5.3 Profiles .10
5.4 Encoder requirements .10
5.5 Decoder requirements.10
Annex A (normative) Encoding and decoding process .12
Annex B (normative) Boxes .17
Annex C (normative) Multi-component decorrelation transformation .25
Annex D (normative) Entropy coding of residual data in the DCT-bypass and large range mode .28
Annex E (normative) Discrete cosine transformation .39
Annex F (normative) Component upsampling .52
Annex G (normative) Quantization and noise shaping for the DCT-bypass process .54
Annex H (normative) Profiles .57
Bibliography .58
© ISO/IEC 2020 – 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).
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 http:// patents .iec .ch).
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.
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 18477-8:2016), which has been
technically revised.
The main changes compared to the previous edition are as follows:
— Annex F.2 has been revised to adopt centred upsampling by default;
— minor editorial changes throughout.
A list of all parts in the ISO/IEC 18477 series can be found on the ISO website.
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.
iv © ISO/IEC 2020 – All rights reserved
Introduction
This document specifies a coded codestream format for storage of continuous-tone high and low
dynamic range photographic content. This is a scalable lossy to lossless image coding system supporting
multiple component images consisting of integer samples between 8- and 16-bit resolution, or floating
point samples of 16-bit resolution. It is by itself an extension of ISO/IEC 18477-6 and ISO/IEC 18477-7,
which specify intermediate range and high-dynamic range image decoding algorithms. Both of these
are based on the box-based file format specified in ISO/IEC 18477-3, which is again an extension of
ISO/IEC 18477-1; the codestream is composed in such a way that legacy applications conforming to
Rec. ITU-T T.81 | ISO/IEC 10918-1 are able to reconstruct a lossy, low dynamic range, 8 bits per sample
version of the image.
Today, the most widely used digital photography format, a minimal implementation of JPEG (specified
in Rec. ITU-T T.81 | ISO/IEC 10918-1), uses a bit depth of 8; each of the three channels that together
compose an image pixel is represented by 8 bits, providing 256 representable values per channel.
For more demanding applications, it is not uncommon to use a bit depth of 16, providing 65 536
representable values to describe each channel within a pixel, resulting in over 2.8×10 representable
colour values. In some less common scenarios, even greater bit depths are used, requiring a floating-
point sample representation.
Most common photo and image formats use an 8-bit or 16-bit unsigned integer value to represent some
function of the intensity of each colour channel. While it might be theoretically possible to agree on
one method for assigning specific numerical values to real world colours, doing so is not practical.
Since any specific device has its own limited range for colour reproduction, the device’s range may be a
small portion of the agreed-upon universal colour range. As a result, such an approach is an extremely
inefficient use of the available numerical values, especially when using only 8 bits (or 256 unique
values) per channel. To represent pixel values as efficiently as possible, devices use a numeric encoding
optimized for their own range of possible colours or gamut.
This document is primarily designed to encode intermediate or high dynamic image sample values
without loss, or with a precisely controllable bounded loss using the tools defined in ISO/IEC 18477-1
and some minimal extensions of those tools. The goal is to provide a backwards-compatible coding
specification that allows legacy applications and existing toolchains to continue to operate on
codestreams conforming to this document.
JPEG XT has been designed to be backwards compatible to legacy applications while at the same time
having a small coding complexity; JPEG XT uses, whenever possible, functional blocks of Rec. ITU-T T.81
| ISO/IEC 10918-1 to extend the functionality of the legacy JPEG coding system. It is optimized for
storage and transmission of intermediate and high dynamic range and wide colour gamut 8- to 16-
bit integer or 16-bit floating point images while also enabling low-complexity encoder and decoder
implementations.
This document is an extension of ISO/IEC 18477-1, a compression system for continuous tone digital
still images which is backwards compatible with Rec. ITU-T T.81 | ISO/IEC 10918-1. That is, legacy
applications conforming to Rec. ITU-T T.81 | ISO/IEC 10918-1 will be able to reconstruct streams
generated by an encoder conforming to this document, though will possibly not be able to reconstruct
such streams in full dynamic range, full quality or without loss.
This document is itself based on ISO/IEC 18477-3 that defines a box-based file format similar to
other JPEG standards. It also contains elements of ISO/IEC 18477-6 and ISO/IEC 18477-7. The aim
of this document is to provide a migration path for legacy applications to support lossless coding of
intermediate and high dynamic range images, that is images that are either represented by sample
values requiring 8- to 16-bit precision, or even using 16-bit floating point sample resolution. While Rec.
ITU-T T.81 | ISO/IEC 10918-1 already defines a lossless mode for integer samples, images encoded in
this mode cannot be decoded by applications only supporting the lossy 8-bit-mode; the coding engine
for lossless coding in Rec. ITU-T T.81 | ISO/IEC 10918-1 is completely different from the lossy coding
mode. Unlike the legacy standard, this document defines a lossless scalable coding engine supporting
all bit depths between 8 and 16 bits per sample, including 16-bit floating point samples, while also
staying compatible with legacy applications. Such applications will continue to work, but will only ab
...
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