[4.2.0] - 2026-07-14

VOD / Random Access

• Added TUNE-VMAF mode targeting ~15% VMAF BD-rate improvement at minimal PSNR loss
• Implemented single-thread processing mode with RA handling
• RA preset tuning and bitrate optimization for M3-M5
• New CLI options: --cqp, --enable-intrabc, --hbd-mds, --enable-kf-tf
• Added raw OBU output format as an alternative to IVF
• Signal initial_display_delay in sequence header to fix A/V sync on seek

RTC / Low Delay

• Added CBR rate control with Kalman-filter QP estimation, cyclic refresh, and frame re-encode
• Added on-the-fly MG size, preset, bitrate, and frame rate changes
• Added reference frame management API with LTR support and two-layer RPS structure
• Exposed --max-intra-bitrate-pct and --max-inter-bitrate-pct parameters
• Improved compression efficiency vs. cycle tradeoff across RTC presets
• Optimized memory footprint for RTC mode with small resolutions
• Further speed and quality tuning for RTC

Encoder (general)

• Refactored entropy coding: direct tile-buffer writes, arithmetic coder simplifications, coefficient shaving
• CDEF optimizations: 8-bit boundary-aware filter, persistent scratch buffers, luma/chroma specialization
• MD and ME optimizations (LPD1 early-skip, VLPD0 fast path, static-block ME bypass)
• Optimized still-image screen content detection
• Optimized TPL dispatch when TPL is disabled
• Added ENABLE_STACK_PROTECTOR CMake option to prevent the stack protector flag from being added

Arm

• Added lowbd (8-bit) int16 forward transform NEON kernels (4x4 through 32x32)
• Added Neon SAD, quantize-matrix, SSIM, VMAF, variance, and pixel projection error kernels
• Added SVE2 VMAF kernels and hardware CRC-32C for hash-based ME
• Optimized convolution, full distortion, and SAD calculation functions

Bug fixes and documentation

• Fixed superres recode crash, RESIZE_DYNAMIC under --rtc, RTC candidate-count overflow, recon output, and memory leak
• Fixed signed left-shift UB, OOB reads, and race conditions in rate control
• Added NVTX/Nsight Systems profiling hooks, PPC toolchain, and macOS universal binary support
• Addressed cppcheck warnings and rewrote affected unit tests
• Addressed USAN and MSAN warnings
• Reduced OBMC stack usage to fix a crash with PGO
• General code cleanup, documentation updates, and test improvements

AV2 is the next-generation video coding specification from the Alliance for Open Media (AOMedia). Building on the foundation of AV1, AV2 is engineered to provide superior compression efficiency, enabling high-quality video delivery at significantly lower bitrates. It is optimized for the evolving demands of streaming, broadcasting, and real-time video conferencing.

This specification serves as the definitive technical reference for AV2 implementations. It outlines the bitstream syntax, semantics, and decoding processes required to ensure full conformance.

AV2 provides enhanced support for AR/VR applications, split-screen delivery of multiple programs, improved handling of screen content, and an ability to operate over a wider visual quality range.