Overview
ISO/IEC 24800-4:2010 - JPSearch Part 4 specifies a file format for metadata embedded in image data (JPEG and JPEG 2000). It defines an interoperable data-exchange mechanism that embeds JPSearch metadata directly into existing image file containers while remaining fully compatible with JPEG-1 (Exif) and JPEG 2000 (JP2/JPX). The standard enables multiple metadata instances, schema registration, and metadata management across devices, repositories and search systems.
Key topics and requirements
- JPSearchMetadata / ElementaryMetadata: Metadata is organized as one or more JPSearchMetadata blocks, each containing one or more ElementaryMetadata blocks. An ElementaryMetadata block holds a single instance of a registered metadata schema, annotation and an encoded Data block.
- Mandatory core metadata: Every compliant file must include at least one ElementaryMetadata whose SchemaIdentifier equals "JPSearch:schema:coremetadata".
- Annotation fields: Annotation includes confidence measure, creation and last-update timestamps (GMT, YYYY/MM/DD-HH:MM:SS), author name (Unicode), and a read-only flag.
- Encoding options: Data encoding is identified by the Encoding byte:
- 'T' (0x54): textual XML instance (recommended) - schema obtained via JPSearch Registration Authority (ISO/IEC 24800-2)
- 'B' (0x42): supplier-defined binary encoding (decode info via Registration Authority)
- NUL (0x00): no encoding specified - follow schema definition
- Container compatibility:
- For JPEG-1, JPSearch metadata is stored in APP3 application marker segments. A single JPSearchMetadata block cannot be split across APP3 segments; multiple APP3 segments may coexist.
- For JPEG 2000, metadata is stored in UUID boxes using the assigned UUID (0x51-35-e9-bb-6f-59-4f-0c-8b-97-7b-47-65-06-49-94). The first four bytes of a JPSearchMetadata block should be checked to verify the box contents.
- Byte order and extensibility: Numeric fields use big-endian. Length fields (LengthOfBlock, LengthOfAnnotation, LengthOfData) enable skipping unknown extensions for forward compatibility.
- Schema registration: Metadata schema must be registered via ISO/IEC 24800-2 (JPSearch Registration Authority).
Practical applications
- Embedding searchable, interoperable metadata directly in images for digital asset management, image repositories, search engines and photo-sharing platforms.
- Supporting social tagging by allowing multiple instances of the same schema authored by different users.
- Enabling consistent metadata exchange between cameras, servers, archives and indexing services while preserving compatibility with existing JPEG and JPEG 2000 workflows.
Who should use it
- Software developers of DAM (digital asset management) systems and image repositories
- Camera and imaging device manufacturers
- Search engine and metadata indexing vendors
- Archivists and cultural heritage institutions needing robust, embedded metadata interoperability
Related standards
Keywords: ISO/IEC 24800-4, JPSearch, metadata embedded in image data, JPEG, JPEG 2000, APP3, UUID box, metadata schema, image metadata interoperability.
Open preview (PDF)Information technology — JPSearch — Part 4: File format for metadata embedded in image data (JPEG and JPEG 2000)
