SVT-AV1 4.0 Boasts Major API Updates
AOMedia’s Software and Implementation Working Group (SIWG) is excited to share that SVT-AV1 4.0, the latest release of its award-winning flagship project, is now available.
SVT-AV1 4.0, released earlier this year, represents a major software update that features a whole host of API improvements, including:
- Extended CRF range to 70, which reduces 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
- Cleaned up public API headers including removal of deprecated macros, structs, and fields
- Added ability to calculate per-frame PSNR and SSIM metrics
- Added tune Image Quality (IQ) and MS-SSIM for Still Image coding mode
- This release boasts notable improvements of compute vs. compression efficiency across all modes, but in particular the AVIF encoding mode. It’s also worth noting that this latest version of the spec adds AC Bias, a psychovisual feature that improves detail preservation and film grain retention.
SVT-AV1 4.0 can be accessed on GitLab, and the SIWG requests that users try it out and report back on their experiences to allow for continuous improvements in SVT-AV1.
A Closer Look at SVT-AV1
The SIWG has been the steward of the SVT-AV1 since 2020, continually evolving and advancing it.
As SVT-AV1 continues to improve, adoption continues to increase. Meta has noted that all its AV1 streams (which cover more than 75% of the watch time of videos on Facebook and Instagram) are produced using SVT-AV1. SVT-AV1 also allowed Meta to stream high-quality short-form videos (Reels) for the first time.
In September 2025, SVT-AV1 won an IBC 2025 Innovation Award in the “Content Everywhere” category. Check out our recent SVT-AV1 highlight video, and take a moment to test version 4.0 on GitLab.
Many thanks to the members of the SIWG for their work advancing this spec.