https://bugs.freedesktop.org/show_bug.cgi?id=79520
--- Comment #15 from Christian König deathsimple@vodafone.de --- Ok that sounds like you updated the OpenGL packages, but not VDPAU right?
Well in this case the reason it doesn't work any more is that OpenGL advertises OpenGL/VDPAU interop, but the VDPAU driver actually isn't new enough end rejects the export request.
Try the --hwdec=no option on mpv.