Overview
ISO/IEC 23094-2:2021 - Information technology - General video coding - Part 2: Low complexity enhancement video coding specifies a standardized method for delivering enhancement-layer video data with intentionally low computational complexity. Published in 2021 by ISO/IEC, this first-edition document defines bitstream formats, decoding and parsing processes, syntax/semantics and normative annexes to enable interoperable enhancement-layer implementations that complement a base coded video signal.
Key topics and technical requirements
The standard focuses on practical, low-complexity enhancement techniques and includes normative specifications for:
- Bitstream and picture formats - container and picture representations for enhancement data and how they relate to source/decoded/output pictures.
- Partitioning, scanning and neighboring relationships - hierarchical organization and residual partitioning that affect decoding and parallel processing.
- Syntax and semantics - tabular syntax descriptions, NAL unit structure, process payloads for sequence, picture and tiled data.
- Decoding processes - step-by-step procedures for enhancement decoding, temporal prediction, dequantization, transforms and residual reconstruction.
- Upscaling kernels and filters - nearest, bilinear, cubic and adaptive cubic upsamplers and the L-1/L-2 residual filtering processes (specified at a procedural level).
- Parsing mechanisms - entropy and prefix decoders, RLE decoding, and Exp-Golomb parsing for coded coefficients and tile metadata.
- Profiles, levels and byte stream formats (normative annexes) - conformance points, byte-stream mapping and a hypothetical reference decoder for validation.
- Supplemental and usability metadata - standardized mechanisms for supplemental enhancement information and video usability information.
These elements are defined in procedural terms (process blocks, tables, and algorithms) to ensure consistent interpretation across hardware and software implementations.
Applications and practical value
ISO/IEC 23094-2:2021 is targeted toward scenarios where improvement of perceived video quality must be achieved with minimal added decoding cost. Typical applications include:
- Low-power mobile and embedded devices where compute and energy budgets are constrained
- Real-time communications (video conferencing) requiring low-latency enhancement layers
- Broadcast or OTT systems delivering enhancement layers to heterogeneous receivers
- Camera and IoT video pipelines that add enhancement frames or resolution layers without heavy processing
- Hardware accelerator and decoder firmware development for enhancement-layer support
Using the standard helps ensure interoperability between encoders and decoders, consistent bitstream handling, and predictable performance across devices.
Who should use this standard
- Codec designers and implementers (software/hardware)
- SoC and consumer electronics manufacturers
- Streaming service engineers and systems integrators
- Standards bodies and testing labs developing conformance suites
Related standards
ISO/IEC 23094-2 is part of the ISO/IEC general video coding family and complements base-layer video coding specifications and ecosystem standards (see normative annexes for profiles, levels and byte-stream mappings).
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