>>105643523
I found this from plebbit, take with a grain of salt.

-auto-alt-ref 1

Activates alternate reference frames. Alternate reference frames are 'invisible' frames, never shown to the user, but which are used as a reference when creating the final frames. This allows the encoder to be a lot more efficient, so always use it. It is the default in the standalone vpxenc libvpx-vp9 encoder as of libvpx 1.9.0 and 1.10.0. -auto-alt-ref 6 can also be used, but this is a -profile 2 thing, so if your HW doesn't support 10-bit HW decoding, it won't work.