Comment 2 for bug 1719150

it works here with igp i965
so this is maybe related to your r600 driver install. Or test purge/reinstall vainfo.

 vainfo
libva info: VA-API version 0.40.0
libva info: va_getDriverName() returns 0
libva info: Trying to open /usr/lib/x86_64-linux-gnu/dri/i965_drv_video.so
libva info: Found init function __vaDriverInit_0_40
libva info: va_openDriver() returns 0
vainfo: VA-API version: 0.40 (libva )
vainfo: Driver version: Intel i965 driver for Intel(R) Skylake - 1.8.3
vainfo: Supported profile and entrypoints
      VAProfileMPEG2Simple : VAEntrypointVLD
      VAProfileMPEG2Simple : VAEntrypointEncSlice
      VAProfileMPEG2Main : VAEntrypointVLD
      VAProfileMPEG2Main : VAEntrypointEncSlice
      VAProfileH264ConstrainedBaseline: VAEntrypointVLD
      VAProfileH264ConstrainedBaseline: VAEntrypointEncSlice
      VAProfileH264ConstrainedBaseline: VAEntrypointEncSliceLP
      VAProfileH264Main : VAEntrypointVLD
      VAProfileH264Main : VAEntrypointEncSlice
      VAProfileH264Main : VAEntrypointEncSliceLP
      VAProfileH264High : VAEntrypointVLD
      VAProfileH264High : VAEntrypointEncSlice
      VAProfileH264High : VAEntrypointEncSliceLP
      VAProfileH264MultiviewHigh : VAEntrypointVLD
      VAProfileH264MultiviewHigh : VAEntrypointEncSlice
      VAProfileH264StereoHigh : VAEntrypointVLD
      VAProfileH264StereoHigh : VAEntrypointEncSlice
      VAProfileVC1Simple : VAEntrypointVLD
      VAProfileVC1Main : VAEntrypointVLD
      VAProfileVC1Advanced : VAEntrypointVLD
      VAProfileNone : VAEntrypointVideoProc
      VAProfileJPEGBaseline : VAEntrypointVLD
      VAProfileJPEGBaseline : VAEntrypointEncPicture
      VAProfileVP8Version0_3 : VAEntrypointVLD
      VAProfileVP8Version0_3 : VAEntrypointEncSlice
      VAProfileHEVCMain : VAEntrypointVLD
      VAProfileHEVCMain : VAEntrypointEncSlice