When appended to a television episode query like "S03E01", it indicates that the file or stream in question has been encoded using this specific architecture, typically wrapped inside a WebM ( .webm ) or Matroska ( .mkv ) container. Why Media Distribution Uses libvpx
The Bay – Season 3, Episode 1 Source: WebRip encoded with libvpx (VP9) Container: WebM the bay s03e01 libvpx