wbthomason [1] filed a orphan request for opencv-contrib [2]:

I have emailed the package owner on June 2 requesting that he update the package and providing an updated PKGBUILD. I have had no response, and the package has been marked as out of date for a long time. From this, I think the maintainer is MIA.

[1] https://aur.archlinux.org/account/wbthomason/ [2] https://aur.archlinux.org/pkgbase/opencv-contrib/