[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