[prometheanfire]

looks like tvheadend doesn't support hwaccl'd transcode https://tvheadend.org/issues/3831

switched to use a postprocess script

bash:
/storage/.kodi/addons/tools.ffmpeg-tools/bin/ffmpegx -init_hw_device vaapi=foo:/dev/dri/renderD128 -hwaccel vaapi -hwaccel_output_format vaapi -hwaccel_device foo -i "${1}" -filter_hw_device foo -vf 'format=nv12|vaapi,hwupload' -c:v h264_vaapi "${1}.mkv" </dev/null 2>&1

mv "${1}.mkv" "${1}"