Hi guys, i just found out MPV is broken for VDPAU on my TAHITI card (AMD Radeon
R9-280), so i'm not sure when was it.

the error is as follow 
Mesa: User error: GL_INVALID_OPERATION in VDPAUMapSurfacesNV
[vo/opengl] after rendering: OpenGL error INVALID_OPERATION.
Mesa: User error: GL_INVALID_OPERATION in VDPAUMapSurfacesNV
[vo/opengl] after rendering: OpenGL error INVALID_OPERATION.
Mesa: User error: GL_INVALID_OPERATION in VDPAUMapSurfacesNV

[vo/opengl] after rendering: OpenGL error INVALID_OPERATION.
Mesa: User error: GL_INVALID_OPERATION in VDPAUMapSurfacesNV

[vo/opengl] after rendering: OpenGL error INVALID_OPERATION.
Mesa: User error: GL_INVALID_OPERATION in VDPAUMapSurfacesNV

[vo/opengl] after rendering: OpenGL error INVALID_OPERATION.
Mesa: User error: GL_INVALID_OPERATION in VDPAUMapSurfacesNV

[vo/opengl] after rendering: OpenGL error INVALID_OPERATION.
Mesa: User error: GL_INVALID_OPERATION in VDPAUMapSurfacesNV
AV: 00:00:02 / 00:20:45 (0%) A-V:  0.000


Exiting... (Quit)
[vo/opengl/vdpau-glx] Before uninitializing OpenGL interop: OpenGL error
INVALID_OPERATION.

MPV settings 
-vo=opengl[-hq] --hwdec=vdpau Filename

MPV works with 
-vo=vdpau --hwdec=vdpau Filename

Mesa/LLVM: today git 3dc2630e457155a4e8c8613911fe178bc4adf743
MPV: Today git d8b27ee4de4e26d594855960a4421b99db9e76ea

If you need more information please include instructions ;) not too saavy here
about Mesa debug and MESA_DEBUG=1 and LIBGL_DEBUG=verbose weren't of much help

TyVM for your hard work.