- tl;dr, playback still seams broken, $ vdpauinfo fails to find a lib
- it is weird how vaapi relies on vdpau backend, hmm
- at least with sw rendering compton doesn't tear

$ pacman -S libva-vdpau-driver libvdpau-va-gl vdpauinfo
$ ln -s /usr/lib/vdpau/libvdpau_va_gl.so.1 /usr/lib/vdpau/libvdpau_i965.so
$ LIBVA_DRIVER_NAME=vdpau mpv --hwdec=vaapi --vo=vaapi

- 2017 update, hw accel works
[kyle@ion ~]$ cat .config/mpv/mpv.conf 
hwdec=vaapi
vo=vaapi