INTERNATIONAL ISO/IEC STANDARD 18181-1 First edition 2022-03 Information technology - JPEG XL image coding system - Part 1: Core coding system Technologies de I'information - Systeme de codage d'images JPEG XL - Partie 1: Systeme de codage de noyau Reference number IEC IS0/IEC 18181-1:2022(E) iSO @ IS0/IEC 2022 IS0/IEC 18181-1:2022(E) COPYRIGHT PROTECTED DOCUMENT @IS0/IEC2022 All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may the internet or an intranet, withoutpriorwrittenpermission.Permission can be requested from eitherIso at the addressbelow or Iso's member body in the country of the requester. ISO copyright office CP 401 · Ch. de Blandonnet 8 CH-1214Vernier,Geneva Phone: +41 22 749 01 11 Email: [email protected] Website: www.iso.org PublishedinSwitzerland i @ IS0/IEC 2022 - All rights reserved IS0/IEC 18181-1:2022(E) Contents Page Foreword .V Introduction. .vi 1 Scope. .1 2 Normative references ..1 3 Terms and definitions 1 3.1 Data storage 2 3.2 Inputs..... 2 3.3 Processes 3 3.4 Image organization .4 3.5 DCT. .5 4 Abbreviated terms. .6 5 Conventions. .6 5.1 Mathematical symbols .6 5.2 Functions. 6 5.3 Operators. .7 5.4 Pseudocode 7 6 Functional concepts .8 6.1 Image organization .8 6.2 Group splitting 8 6.3 Codestream and bitstream. 9 6.4 Multiple frames 10 6.5 Mirroring 10 7 Encoder requirements. .10 8 Decoder requirements. .10 9 Codestream .10 9.1 Syntax. 10 9.1.1 Reading a field 11 9.1.2 Initializing a field 11 9.2 Field types 11 9.2.1 u(n) 11 9.2.2 U32(d0, d1, d2, d3) 11 9.2.3 U640. 11 9.2.4 VarintO 12 9.2.5 U80 12 9.2.6 F160 12 9.2.7 Boolo 12 9.2.8 Enum(EnumTable) 12 9.2.9 ZeroPadToByte) 13 9.3 Structure .13 10 Decoding process .13 Annex A (normative) Headers. ..15 Annex B (normative) IcC profile .25 AnnexC(normative)Frames ..32 Annex D (normative) Entropy decoding .58 Annex E (normative) Weighted predictor .67 Annex F (normative) Adaptive quantization .70 Annex G (normative) Chroma from luma .71 @ IS0/IEC 2022 - All rights reserved iii IS0/IEC 18181-1:2022(E) Annex H (normative) Extensions. ..72 Annex I (normative) Integral transforms ..73 Annex J (normative) Restoration filters ..84 Annex K (normative) Image features ..87 Annex L (normative) Colour transforms ..92 Annex M (informative) Encoder overview. 86" Bibliography. 101 iv ISO/IEC2022-Allrightsreserved IS0/IEC 18181-1:2022(E) Foreword ISO (the International Organization for Standardization) and IEC (the International Electrotechnical Commission)formthespecializedsystemforworldwidestandardization.Nationalbodiesthatare 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 https://patents.iec.ch). Any trade name used in this document is information given for the convenience of users and d