Hi, 
I do not know how to proceed - maybe somebody can help. 
 
I have a Gemini Lake R J4125 with installed Intel i965 driver for Intel(R) Gemini Lake - 2.3.0.
Vainfo is showing proper installation. Details attached. 
(Kernel 4.19.0-14-amd64, Linux Debian GNU/Linux 10 \n \l )
I have the latest version of tvheadend built and installed (v4.3-1947~gdbaa0f850, enabled static-ffmpeg) 
Ordinary, non hw accelerated, codecs are working without problems.  
vapi-codec for x264,x265,vp8,vp9 are offered in the stream/codec tab. 
I can add the vapi codecs - but they stay disabled. I get no further debug-info!
Any hints? 
Thx in advance, Oli
################################ vainfo #################################
root@BK55:~# vainfo
error: XDG_RUNTIME_DIR not set in the environment.
error: can't connect to X server!
libva info: VA-API version 1.4.0
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_1_4
libva info: va_openDriver() returns 0
vainfo: VA-API version: 1.4 (libva 2.4.0)
vainfo: Driver version: Intel i965 driver for Intel(R) Gemini Lake - 2.3.0
vainfo: Supported profile and entrypoints
      VAProfileMPEG2Simple            : VAEntrypointVLD
      VAProfileMPEG2Main              : VAEntrypointVLD
      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
      VAProfileHEVCMain10             : VAEntrypointVLD
      VAProfileHEVCMain10             : VAEntrypointEncSlice
      VAProfileVP9Profile0            : VAEntrypointVLD
      VAProfileVP9Profile0            : VAEntrypointEncSlice
      VAProfileVP9Profile2            : VAEntrypointVLD