Hi,
We have steps to launch USB cameras on Jetson platforms:
Jetson Nano FAQ
Q: I have a USB camera. How can I launch it on Jetson Nano?
If the source supports YUV422 format, it can be run without extra memory copy from CPU buffers to NVMM buffers(NvBuffer). If it does not support YUV422, you would need to use appsrc and convert/copy the data to NVMM buffers. In this case, it takes certain CPU usage.