What OS do you have, and how did you install TVHeadend?
You may just want to get a version of FFmpeg that works, then create a Spawn stream profile using it.
I transcode with the N100. I installed TVHeadend through the Linuxserver Docker image -- this image already includes a working FFmpeg binary at /usr/bin/ffmpeg. Just pass "/dev/dri" through to the container in your docker-compose file, so the container can use your render devices:
devices:
- /dev/dri:/dev/dri
Then, in the TVHeadend web interface, add a new stream profile of type "MPEG-TS Spawn/built-in" and use something like the following in the "Command line" box:
/usr/bin/ffmpeg -loglevel fatal -init_hw_device qsv=hw -filter_hw_device hw -i pipe:0 -vf 'hwupload=extra_hw_frames=64,format=qsv' -c:v hevc_qsv -c:a copy -f mpegts pipe:1
See https://trac.ffmpeg.org/wiki/Hardware/QuickSync to better customize this command.
