This website https://pyav.org/docs/stable/ is not updated, it has version 9.0.2 and not 13.1.0 (like it's on https://pyav.basswood-io.com/docs/stable/ ). I find it via google (top google link when searching for pyav), and using it caused issues while installing library (I pinned version, which was obviously old). I wasted maybe an hour until I figured it out :-) Thanks