ISO/IEC 18181-1:2022/Amd 1:2022

Overview

ISO/IEC 18181-1:2022/Amd 1:2022 is an important amendment to the JPEG XL image coding system standard, specifically addressing profiles and levels within the core coding system. Published by ISO in June 2022, this update promotes interoperability by defining a standardized "Main" profile for JPEG XL images, facilitating consistent implementation and broad compatibility across various devices and software platforms.

This amendment enhances the original Part 1 standard by introducing specific profiles and levels that streamline image encoding and decoding. It is a critical guideline for developers, manufacturers, and software vendors who work with JPEG XL, aiming for optimized image coding performance, consistency, and efficiency.

Key Topics

• Main Profile Definition:
  A single profile called “Main” is introduced to support a wide range of applications such as mobile phones, web browsers, and image editing software. This profile encapsulates all coding tools described in the core standard.

• Levels Specification:
  The Main profile defines two levels:

  • Level 5: Optimized for end-user image delivery scenarios including mobile apps and web browsers.
  • Level 10: Designed for high-demand use cases such as image authoring, print media, scientific imaging, and satellite imagery.

• Backward Compatibility:
  Decoders supporting a higher level (e.g., Level 10) automatically support all lower levels, ensuring smooth interoperability across devices with varying capabilities.

• Threshold Parameters:
  Levels set limits on key parameters such as:

  • Maximum image width and height (pixels)
  • ICC profile size (bytes)
  • Bits per sample (color depth)
  • Number of splines and patches for image overlays
  • Number of modular transforms and channels
  • Maximum tree depth and frame durations for modular encoding

• Normative Annex N:
  Annex N is added to the standard as a normative section detailing these profiles and levels to ensure conformity and implementation uniformity.

Applications

• Mobile Devices:
  The Main profile Level 5 suits everyday usage on smartphones and tablets where efficient image delivery and compact file size are crucial.

• Web Browsers:
  Browsers implementing JPEG XL support through this amendment benefit from enhanced compression and high-quality image rendering with guaranteed compatibility.

• Image Editing Software:
  Level 10 supports complex workflows requiring high bit depth and large image dimensions, enabling professional photo editing and scientific image processing.

• Printing and Publishing:
  High fidelity imaging needed in print media can leverage Level 10 for rich color information and precise image representation.

• Scientific and Satellite Imaging:
  Demanding applications with large image data sets and high precision can utilize the scalability of Level 10, handling large multi-channel images efficiently.

Related Standards

• ISO/IEC 18181 Series:
  Part 1 forms the core JPEG XL coding system, with additional parts covering transport, container formats, and conformance testing.

• ICC Profile Standards:
  Referenced in the amendment for managing color profiles crucial for accurate color reproduction in JPEG XL images.

• ISO/IEC Directives Part 1 & 2:
  Governing documents describing the development and maintenance procedures for ISO/IEC standards, ensuring global consensus and quality.

• Other Image Coding Standards:
  JPEG XL complements older standards like JPEG, JPEG 2000, and newer standards such as AVIF and HEIC, focusing on advanced compression efficiency and flexibility.

Keywords: ISO/IEC 18181-1:2022/Amd 1, JPEG XL image coding system, profiles and levels, image compression standard, Main profile JPEG XL, image coding interoperability, JPEG XL core coding system, image decoder compatibility, Level 5 JPEG XL, Level 10 JPEG XL, modular encoding thresholds, ICC profile size, high bit-depth imaging.