High CPU usage for video capturing

You may try to use nvv4l2camerasrc. Please check
Jetson Nano FAQ
[Q: I have a USB camera. How can I launch it on Jetson Nano?]

This may reduce partial CPU loading. The optimal solution is to pass NVMM buffers from source to sink, but it only accepts CPU buffers in v4l2sink. Certain CPU loading is expected in this usecase.