Firefox Gets AV1 VA-API Acceleration Sorted Out
After working on it the past month, the necessary bits have come together for supporting AV1 VA-API playback within Firefox on Linux. See the Mozilla.org BugZilla for tracking the progress on the effort. The latest AV1 activity in general for Mozilla can be tracked via hg.mozilla.org.
This follows FFmpeg already supporting AV1 VA-API. Granted, in order to enjoy GPU-accelerated AV1 with VA-API you need to be using the latest-generation Intel graphics or AMD Radeon RX 6000 "RDNA2" GPUs paired with Mesa 21.3 or newer with AMD having squared away their support at the end of summer.
The NVIDIA GeForce RTX 30 series does support AV1 too but there is exposed via NVDEC and VDPAU while there is an experimental translation layer for VA-API to NVDEC but that doesn't yet support AV1.