[4.0.0] - 2026-1-23

API updates

• Major release with new API updates that are not backwards compatible.
• Extended the crf range to 70 reducing the impact or QP scaling allowing the encoder to reach lower bitrates
• Added quarter steps between crf increments to allow for further granularity in qp selection
• Added support for setting a custom global logger for library consumers (!2570 (merged), !2579 (merged))
• Cleaned up public API headers including removal of deprecated macros, structs, and fields (!2565 (merged), !2568 (merged))
• Additionally cleaned up anything marked using SVT_AV1_CHECK_VERSION().
• Added ability to calculate per-frame PSNR and SSIM metrics (!2521 (merged))
• Allow sending more than 1 but less than 4 frames with avif mode (This is not for AVIF image sequence, but for encoding an alpha layer) (!2551 (merged), !2560 (merged))
• Added tune IQ and MS-SSIM for Still Image coding mode

Encoder

• Significant improvements in AVIF and still image modes (!2552 (merged),!2567 (merged)):
• ~5-8x speedup M11-M0 at the same quality levels with tune MS-SSIM
• ~5-8% BD-Rate improvements at the same complexity with tune MS-SSIM
• Tradeoff improvements for the RTC modes (!2558 (merged)):
• ~5-15% speedup at similar quality levels in --rtc mode across presets 7 - 11
• Tradeoff improvements for the Random Access mode (VOD use case) showing a 10-25% speedup across presets M7 down to M0 for --fast-decode 1 and 2 (!2558 (merged))
• Major feature updates for the visual quality mode with the completion porting all SVT-AV1-PSY applicable features for --tune vq for video and --tune iq for avif (!2484 (merged), !2489 (merged), !2491 (merged), !2494 (merged), !2496 (merged), !2503 (merged), !2504 (merged), !2507 (merged), !2514 (merged), !2522 (merged) , !2561 (merged), !2562 (merged), !2576 (merged)):
• Added AC Bias, a psychovisual feature that improves detail preservation and film grain retention
• Update S-Frame support to allow setting it in a specific decode order option and with more qp options (!2477 (merged) !2523 (merged) !2534 (merged))
• Further Arm Neon and SVE2 optimizations that improve high bitdepth encoding by an average of ~5% in low resolutions