ISO/IEC 21122-3:2022 - Overview
ISO/IEC 21122-3:2022 specifies transport and container formats for JPEG XS, the low-latency, lightweight image coding system. This part of the JPEG XS family defines how JPEG XS codestreams (as defined in ISO/IEC 21122-1) are packaged in files and embedded in transport streams to support still images and motion image sequences on computer platforms and over the internet. The second edition updates the original standard (including corrigenda and support signalling for 4:2:0 images).
Key topics and technical requirements
- Container formats: Normative specifications for a still-image file format (JXS) and mechanisms to encapsulate JPEG XS codestreams using a box-based structure (influenced by JPEG 2000 box syntax).
- Integration with existing file formats:
- Transport embedding: Guidance for embedding codestreams in transport streams to enable internet-based communication and low-latency delivery.
- Metadata and colour signalling:
- Defines metadata boxes for image properties (colourspace, tonescale), intellectual property info, and vendor metadata.
- Requires containers/transport to signal correct colourspace (using coding-independent code points / Rec. ITU‑T H.273 | ISO/IEC 23091-2).
- Conformance and robustness:
- Readers must ignore unrecognized boxes, ensuring forward compatibility.
- This part takes precedence over base formats where differences exist.
- Annexes (normative):
- Annex A - JXS still-image file format
- Annex B - JPEG XS in ISOBMFF (movies)
- Annex C - JPEG XS in HEIF
- Annex D - Media Type registration and use outside file formats
Practical applications and users
- Use cases:
- Live production, broadcast contribution, and remote monitoring where minimal latency and robust recompression are critical.
- Real-time streaming, virtual production, and low-latency remote collaboration.
- Archiving and editing workflows that require lightweight, visually lossless compression with reliable metadata.
- Who benefits:
- Codec and player developers, container/format implementers, and application developers.
- Broadcast and streaming engineers integrating JPEG XS into transport chains.
- Hardware vendors building low-latency encoders/decoders for cameras, live-switchers, and capture devices.
- Content creators and post-production houses requiring efficient, low-latency intermediate formats.
Related standards
Keywords: JPEG XS, ISO/IEC 21122-3:2022, transport and container formats, JXS, ISOBMFF, HEIF, low-latency image coding, codestream, metadata, colourspace.