Overview - ISO/IEC TR 23002-8:2021 (MPEG video technologies)
ISO/IEC TR 23002-8:2021 is a technical report from ISO/IEC that documents working practices for using objective metrics in the evaluation of video coding efficiency experiments. It describes how the video coding community (MPEG, VCEG, JVET/JCT-VC) has been applying the Bjøntegaard delta bit rate (BD-rate) method, primarily using PSNR-based measurements, to compare codec performance across multiple bit rates. The report provides concept-level guidance, practical calculation steps and notes on special cases such as HDR/WCG and 360° video. It is informational (no normative references) and does not prescribe subjective quality assessment methods.
Key topics and technical requirements
- BD-rate definition: BD-rate is defined as the average percentage bit‑rate difference at equal measured distortion, integrated across a range of bit rates in the log domain.
- PSNR-based BD-rate process: Stepwise procedure covering:
- Calculation of per-frame PSNR (luma and chroma).
- Aggregation to per-sequence PSNR and bit‑rate values for multiple QP (quantization parameter) points.
- Computation of per-sequence BD-rate and an aggregate BD-rate across sequences.
- PSNR details: Formulae and handling rules for PSNR and MSE (including bit-depth considerations and zero-MSE edge cases).
- Chroma vs luma: Guidance to report Y (luma) and chroma fidelities and to interpret trade-offs (avoid luma gains at undue chroma cost).
- Alternatives and caveats: Notes on other objective metrics (SSIM, MS-SSIM, VMAF) and when subjective testing is required - especially for large perceptual differences or tools that mainly affect visual artifacts (e.g., deblocking).
- Special material: Additional considerations for HDR material and 360° video BD-rate calculations.
Applications and who uses this standard
- Codec researchers and developers: To compare encoder tool changes consistently across operating points during standard development (HEVC, VVC, AVC contexts).
- Standards committees and test teams: For reproducible reporting of coding efficiency in call-for-proposals, verification testing and collaborative evaluations.
- R&D labs and performance analysts: When objective benchmarking is needed for iterative encoder optimization before conducting formal subjective tests.
- Product teams: To understand expected bitrate savings or regressions when enabling/disabling coding tools.
Related standards and context
- Works in the MPEG/ITU-T ecosystem and references codec families such as AVC (H.264 / ISO/IEC 14496-10), HEVC (H.265 / ISO/IEC 23008-2) and VVC (H.266 / ISO/IEC 23090-3) as relevant context. It is based on JVET documents (e.g., JVET‑Q0826).
Keywords: ISO/IEC TR 23002-8:2021, BD-rate, PSNR, video coding efficiency, MPEG, HDR, 360° video, codec benchmarking, objective metrics, video quality evaluation.