1、BSI Standards Publication BS ISO/IEC 18477-3:2015 Information technology Scalable compression and coding of continuous-tone still images Part 3: Box file formatBS ISO/IEC 18477-3:2015 BRITISH STANDARD National foreword This British Standard is the UK implementation of ISO/IEC 18477-3:2015. The UK pa
2、rticipation in its preparation was entrusted to Technical Committee IST/37, Coding of picture, audio, multimedia and hypermedia information. A list of organizations represented on this committee can be obtained on request to its secretary. This publication does not purport to include all the necessa
3、ry provisions of a contract. Users are responsible for its correct application. The British Standards Institution 2015. Published by BSI Standards Limited 2015 ISBN 978 0 580 87487 1 ICS 35.040 Compliance with a British Standard cannot confer immunity from legal obligations. This British Standard wa
4、s published under the authority of the Standards Policy and Strategy Committee on 31 December 2015. Amendments/corrigenda issued since publication Date T e x t a f f e c t e dBS ISO/IEC 18477-3:2015 Information technology Scalable compression and coding of continuous-tone still images Part 3: Box fi
5、le format Technologies de linformation Compression chelonnable et codage dimages plates en ton continu Partie 3: Format de la liste de fichiers INTERNATIONAL STANDARD ISO/IEC 18477-3 Reference number ISO/IEC 18477-3:2015(E) First edition 2015-12-15 ISO/IEC 2015 BS ISO/IEC 18477-3:2015ii ISO/IEC 2015
6、 All rights reserved COPYRIGHT PROTECTED DOCUMENT ISO/IEC 2015, Published in Switzerland All rights reserved. Unless otherwise specified, 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 t
7、he internet or an intranet, without prior written permission. Permission can be requested from either ISO at the address below or ISOs member body in the country of the requester. ISO copyright office Ch. de Blandonnet 8 CP 401 CH-1214 Vernier, Geneva, Switzerland Tel. +41 22 749 01 11 Fax +41 22 74
8、9 09 47 copyrightiso.org www.iso.org ISO/IEC 18477-3:2015(E)BS ISO/IEC 18477-3:2015ISO/IEC 18477-3:2015(E)Foreword iv Introduction v 1 Scope . 1 2 Normative references 1 3 Terms, definitions, abbreviated terms and symbols . 1 3.1 Terms and definitions . 1 3.2 Symbols . 5 3.3 Abbreviated terms . 6 4
9、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 High level overview on JPEG XT ISO/IEC 18477-3 8 5.2 Encoder r
10、equirements 8 5.3 Decoder requirements 9 Annex A (normative) JPEG XT marker segment .10 Annex B (normative) Common box types .15 Annex C (normative) Point transformation .39 Annex D (normative) Checksum computation 41 Bibliography .42 ISO/IEC 2015 All rights reserved iii Contents PageBS ISO/IEC 1847
11、7-3:2015ISO/IEC 18477-3:2015(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 Intern
12、ational 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
13、with ISO and IEC, also take part in the work. In the field of information technology, ISO and IEC have established a joint technical committee, ISO/IEC JTC 1. The procedures used to develop this document and those intended for its further maintenance are described in the ISO/IEC Directives, Part 1.
14、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 o
15、f 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 recei
16、ved (see www.iso.org/patents). Any trade name used in this document is information given for the convenience of users and does not constitute an endorsement. For an explanation on the meaning of ISO specific terms and expressions related to conformity assessment, as well as information about ISOs ad
17、herence to the WTO principles in the Technical Barriers to Trade (TBT) see the following URL: Foreword - Supplementary information The committee responsible for this document is ISO/IEC JTC 1, Information technology, SC 29, Coding of audio, picture, multimedia and hypermedia information. ISO/IEC 184
18、77 contains the following parts under the general title Information technology Scalable compression and coding of continuous-tone still images: Part 1: Scalable compression and coding of continuous-tone still images Part 2: Extensions for high dynamic range images Part 3: Box file format Part 6: IDR
19、 Integer Coding Part 7: HDR Floating-Point Coding Part 8: Lossless and Near-lossless Coding Part 9: Alpha Channel Coding The following parts are under preparation: Part 4: Conformance testing Part 5: Reference softwareiv ISO/IEC 2015 All rights reservedBS ISO/IEC 18477-3:2015ISO/IEC 18477-3:2015(E)
20、Introduction This part of ISO/IEC 18477 specifies an extensible file format, denoted as JPEG XT, which is built on top of the existing Rec. ITU-T T.81 | ISO/IEC 10918-1 codestream definition. While typically file formats encapsulate codestreams by means of additional syntax elements such as boxes, t
21、he file format structure specified here rather embeds the syntax elements of the file format, called boxes, into the codestream. The necessity for this unusual arrangement is the backwards compatibility to the legacy standard and the application toolchain built around it; that is, legacy application
22、s conforming to Rec. ITU-T T.81 | ISO/IEC 10918-1 will be able to decode image information embedded in files conforming to the family of ISO/IEC 18477 standards, though will only be able to recover a three component, 8 bits per sample, lower quality version of the image described by the full file. F
23、or 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 on over 2,8 10 14representable colour values. In some less common scenarios, even greater bit depths are used, and sometimes the dynam
24、ic range of the image is so high that a floating point based encoding is desirable. In addition to image information, some applications also require an additional opacity channel, a feature not available from the legacy standard. Most common photo and image formats use an 8-bit or 16-bit unsigned in
25、teger 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 rep
26、roduction, the devices 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 efficient
27、ly as possible, devices use a numeric encoding optimized for their own range of possible colours or gamut. JPEG XT is designed to extend the legacy JPEG standard towards higher bitdepth, higher dynamic range, wide colour gamut content while simultaneously allowing legacy applications to decode the i
28、mage data in the codestream to a standard low dynamic range image represented by only eight bits per channel. 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 the family of I
29、SO/IEC 18477 standards. 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 S
30、ystem. This part of ISO/IEC 18477 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 recon
31、struct streams generated by an encoder conforming to this part of ISO/IEC 18477, though will possibly not be able to reconstruct such streams in full dynamic range, full quality or other features defined in this part of ISO/IEC 18477. The aim of this part of ISO/IEC 18477 is to provide a flexible an
32、d extensible framework to enrich ISO/IEC 18477-1 compliant codestreams with side-channels and metadata. The syntax chosen in this part of ISO/IEC 18477 defines a mechanism to embed syntax elements denoted as “Boxes” into Rec. ITU-T T.81 | ISO/IEC 10918-1 compliant codestreams. The box syntax used he
33、re is identical to that defined in the JPEG family of standards, for example JPEG 2000 (Rec. ITU-T T. 800 | ISO/IEC 15444-1). Boxes will then carry either additional image data, to enable encoding of images of higher bitdepth, high dynamic range, include alpha channels etc., or will carry metadata t
34、hat describes the decoding process of the legacy Rec. ITU-T T.81 | ISO/IEC 10918-1 codestream and the side channels to an extended or high dynamic range image. ISO/IEC 2015 All rights reserved vBS ISO/IEC 18477-3:2015BS ISO/IEC 18477-3:2015Information technology Scalable compression and coding of co
35、ntinuous-tone still images Part 3: Box file format 1 Scope This part of ISO/IEC 18477 specifies a coding format, referred to as JPEG XT, which is designed primarily for continuous-tone photographic content. 2 Normative references The following documents, in whole or in part, are normatively referenc
36、ed in this document and are indispensable for its application. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies. ISO/IEC 10646, Information technology Universal Coded Character Set (UCS) ISO
37、/IEC 18477-1:2015, Information technology Scalable compression and coding of continuous-tone still images Part 1: Scalable compression and coding of continuous-tone still images Rec. ITU-T T.81 | ISO/IEC 10918-1, Information Technology Digital Compression and Coding of Continuous Tone Still Images R
38、equirements and Guidelines Rec. ITU-T T.871 | ISO/IEC 10918-5, Information technology Digital compression and coding of continuous-tone still images: JPEG File Interchange Format 3 Terms, definitions, abbreviated terms and symbols 3.1 Terms and definitions For the purposes of this document, the foll
39、owing terms and definitions apply. 3.1.1 ASCII encoding encoding of text characters and text strings according to ISO/IEC 10646 3.1.2 base decoding path process of decoding legacy codestream and refinement data to the base image, jointly with all further steps until residual data is added to the val
40、ues obtained from the residual codestream 3.1.3 base image collection of sample values obtained by entropy decoding the DCT coefficients of the legacy codestream and the refinement codestream, and inversely DCT transforming them jointly 3.1.4 binary decision choice between two alternatives INTERNATI
41、ONAL ST ANDARD ISO/IEC 18477-3:2015(E) ISO/IEC 2015 All rights reserved 1BS ISO/IEC 18477-3:2015ISO/IEC 18477-3:2015(E) 3.1.5 bit stream partially encoded or decoded sequence of bits comprising an entropy-coded segment 3.1.6 block 8 8 array of samples or an 8 8 array of DCT coefficient values of one
42、 component 3.1.7 box structured collection of data describing the image or the image decoding process embedded into one or multiple APP 11marker segments Note 1 to entry: See Annex A for the definition of boxes 3.1.8 byte group of 8 bits 3.1.9 coder embodiment of a coding process 3.1.10 coding encod
43、ing or decoding 3.1.11 coding model procedure used to convert input data into symbols to be coded 3.1.12 (coding) process general term for referring to an encoding process, a decoding process, or both 3.1.13 compression reduction in the number of bits used to represent source image data 3.1.14 compo
44、nent two-dimensional array of samples having the same designation in the output or display device. An image typically consists of several components, e. g. red, green and blue 3.1.15 continuous tone image image whose components have more than one bit per sample 3.1.16 decoder embodiment of a decodin
45、g process 3.1.17 decoding process process which takes as its input compressed image data and outputs a continuous-tone image 3.1.18 encoder embodiment of an encoding process2 ISO/IEC 2015 All rights reservedBS ISO/IEC 18477-3:2015ISO/IEC 18477-3:2015(E) 3.1.19 encoding process process which takes as
46、 its input a continuous-tone image and outputs compressed image data 3.1.20 entropy decoder embodiment of an entropy decoding procedure 3.1.21 entropy decoding lossless procedure which recovers the sequence of symbols from the sequence of bits produced by the entropy encoder 3.1.22 entropy encoder e
47、mbodiment of an entropy encoding procedure 3.1.23 entropy encoding lossless procedure which converts a sequence of input symbols into a sequence of bits such that the average number of bits per symbol approaches the entropy of the input symbols 3.1.24 high dynamic range image or image data comprised
48、 of more than eight bits per sample 3.1.25 Intermediate dynamic range image or image data comprised of more than eight bits per sample 3.1.26 Joint Photographic Experts Group JPEG informal name of the committee which created this part of ISO/IEC 18477 Note 1 to entry: The “joint” comes from the ITU
49、and ISO/IEC collaboration. 3.1.27 legacy codestream collection of markers and syntax elements defined by Rec. ITU-T T.81 | ISO/IEC 10918-1 bare any syntax elements defined by the family ISO/IEC 18477 standards Note 1 to entry: That is, the legacy codestream consists of the collection of all markers except those APP 11markers that describe JPEG XT boxes by the syntax defined in Annex A. 3.1.28 legacy decoding path collection of operations to be performed on the entrop
