The question is if the version of FFMPEG you're using support Nvidia GPU acceleration. I have no idea if the version that ships with Serviio does. If you're using Windows, you can get different versions of FFMPEG from this web site. You can also get the build files and ensure your version supports it, but that's over my head to do that.
Hi thanks for the help. I already "installed" the full version "ffmpeg-git-full.7z" + user.vmoptions (which was empty) -> entered -Dserviio.useNVidiaAcceleration and saved. But it doesn't use the gpu :/