Mine shows installed and up to date. I reinstalled with same issues.
$ sudo pacman -S libva-vdpau-driver
[sudo] password for mapman97:
warning: libva-vdpau-driver-0.7.4-6 is up to date – reinstalling
resolving dependencies…
looking for conflicting packages…
Packages (1) libva-vdpau-driver-0.7.4-6
Total Download Size: 0.04 MiB
Total Installed Size: 0.08 MiB
Net Upgrade Size: 0.00 MiB
Thanks for making me look closer one more time. Changing output fixed my issue.
You mentioned you use nvidia. I had a simular issue with vlc awhile ago crashing when trying to play mkv files, and what fixed it for me was going into vlc video settings and changing the video output from automatic to VDPAU output.