The transcoder (CPU) must read through the file and find the information.
If you have Chapter Thumbnails on (enabled by default) and Chapter Indexes (enabled by default), and Credit / Intro detection, it must read the file, grab the frames / time stamps, and write them to the DB.
The GPU is not capable of writing to the DB on its own. It lives in its OpenCL world.
It’s a background task anyway. If you look at the process priority, you’ll find it’s been 'nice’d lower.
