ISO/IEC 14495-2:2003

Overview

ISO/IEC 14495-2:2003 specifies extensions to lossless and near‑lossless compression methods for continuous‑tone still images (including bi‑level, gray‑scale, and colour). Part 2 extends the baseline model with additional coding tools and operational modes - for example arithmetic coding, enhanced near‑lossless handling, extended prediction schemes, Golomb coding extensions, fixed‑length coding and sample transformations for inverse colour transforms. The standard also defines coded representations, compressed data formats and provides practical implementation guidance and conformance testing procedures.

Key topics and technical requirements

• Extensions to encoding/decoding processes
  • Arithmetic coding procedures and binary arithmetic encoder/decoder flows (Annexes A & B).
  • Extensions to prediction algorithms including edge‑detecting predictors and prediction correction.
  • Golomb coding extensions and run‑interruption handling.
• Near‑lossless coding
  • Methods where reconstruction error per sample is bounded by a predefined value; includes visual quantization and NEAR parameter handling.
• Sample transformation
  • Support for inverse colour transforms to map reconstructed samples back to original colour components.
• Compressed data format and interchange
  • Marker assignments, preset parameter syntax and minimum coded unit (MCU) handling for multi‑component images (Annex G).
• Operational modes and coding options
  • Line‑interleaved and sample‑interleaved modes, fixed‑length coding (FLC) and restart interval procedures.
• Conformance and implementation
  • Encoder and decoder conformance tests, test images and procedures (Annex I), plus patent and bibliographic references (Annexes J & K).
• Guidance for implementers
  • Detailed flow diagrams, initialization rules, context determination and update rules to support practical implementations.

Applications

ISO/IEC 14495-2:2003 is relevant for systems and applications that need efficient, bit‑preserving or bounded‑error compression of still images, including:

• Medical imaging, remote sensing and archival systems that require lossless preservation.
• Digital photography pipelines and scanners where near‑lossless tradeoffs reduce bitrate with controlled quality loss.
• Imaging software libraries, codecs and hardware accelerators implementing JPEG‑LS style algorithms.
• Interchange formats and storage systems that require standardized compressed representations and conformance testing.

Who should use this standard

• Software and hardware codec developers implementing lossless/near‑lossless image compression.
• System integrators building archival, medical or remote sensing imaging pipelines.
• QA teams and standards bodies conducting conformance testing and interoperability validation.

Related standards

• ISO/IEC 14495-1 (Baseline): foundational baseline specifications for lossless and near‑lossless compression.
• Identical text published as ITU‑R Recommendation T.870 (as noted in the document).