Encoding encoded video?

[mtbest]

I use two Logitech BRIO 4k usb 3.0 cameras that perform video encoding on-board.
What happens in OBS in such a case? Does OBS decode and then re-encode the video for streaming?
When I use NVENC encoder on my Nvidia card, both the GPU and CPU are busy with my BRIO cameras. But when I use "software x264" encoder, activity on both GPU and CPU drops significantly. Does this mean that my cameras use x264 encoding and OBS just passes through encoded video without extra encoding? I think it is useful to know if (and how) we can use already-encoded video inputs.
Thank you for your insight

 

[TryHD]

Does this mean that my cameras use x264 encoding and OBS just passes through encoded video without extra encoding?

No, there is no passthrough

I think it is useful to know if (and how) we can use already-encoded video inputs.
Thank you for your insight

they all work the same, OBS will decode the video input, composit it in your scene and than encodes it again.