Overview
ISO/IEC 21122-5:2022 defines the reference software for JPEG XS - a low‑latency, lightweight image coding system. Part 5 of the ISO/IEC 21122 series provides a reference decoder and a sample encoder implementation that act as an implementation guideline and a validation anchor for conformance testing. The second edition (2022) updates the packaged reference software and is published alongside the normative core and profile documents.
Key topics and requirements
- Reference implementation: Includes a decoder that produces the normative decoded output and a sample encoder capable of generating codestreams conforming to ISO/IEC 21122‑1 and ISO/IEC 21122‑2.
- Conformance and testing: The reference decoder enables output comparison for conformance testing (see ISO/IEC 21122‑4). It can also validate syntactic correctness of codestreams, but its use does not replace formal conformance procedures.
- Software package: The reference software is provided (xs_ref_sw_ed2.zip) and is written in C11. Annex A gives build/unpack instructions; a README and LICENSE.md are included.
- File format support: Annex B documents input/output image file formats supported by the software (notably PGX and NetPBM (PGM/PPM)), describing headers, raw data layout and bit‑depth handling.
- Usage guidance: Annex C (informative) explains usage examples. The document explicitly warns that the reference software is not recommended for production due to limited protection against memory and code‑execution exploits.
- Intellectual property: The standard draws attention to potential patent claims and points users to ISO/IEC patent declaration resources; license terms for the reference software are in LICENSE.md.
Applications and who should use it
- Standards implementers: Developers building JPEG XS encoders and decoders can use the reference code as a starting point or validation anchor.
- Test labs and QA teams: Use the reference decoder to compare outputs for conformance testing and to verify codestream syntax before formal testing per ISO/IEC 21122‑4.
- Researchers and evaluators: Assess encoding quality examples and produce conforming codestreams for experimentation.
- Tool vendors and integrators: Learn file I/O conventions (PGX/NetPBM) and sample build steps for cross‑platform support.
Related standards
Keywords: ISO/IEC 21122‑5:2022, JPEG XS, reference software, low‑latency image coding, C11 reference implementation, conformance testing, PGX, NetPBM, encoder, decoder, JPEG XS reference.