cpu load without client stream

[int2018]

Question

Hallo,

I have a little pi zero 1 running bookworm and there is also a pi cam attached. I used rpicam-vid for stream testing an then tested mediamtx and a little webrtc webpage. I works quite well and I think I run it as a service but then I discovered that even without any clients it takes a good amount of cpu load. top jumps from 13% to 65% after starting mediamtx.
And this is my question: Why?
I would understand that there is lot to do when some client requests a stream, either vlc rtsp or browser page webtrc. But why is the idle load so high an how can I reduce that?
Thanks for a hint... :-)