Hi,
We are able to see steady fps. You may enable hardware converter at max clock and try again:
Nvvideoconvert issue, nvvideoconvert in DS4 is better than Ds5? - #3 by DaneLLL
The capability is listed in
https://developer.nvidia.com/jetson-xavier-nx-data-sheet
h264 and h265 encoding can achieve 10x 1080p60