Running `gst-inspect-1.0 nvv4l2h264dec` will show that there is no such element as `nvv4l2h264dec`

[DaneLLL]

Hi,
gst-launch-1.0 + appsink is not a valid use-case, so it may not work properly.

Looks like your system is at an unknown status, please re-flash it and use default OpenCV package to run
Doesn't work nvv4l2decoder for decoding RTSP in gstreamer + opencv - #3 by DaneLLL

Please replace the url with yours. Would suggest run 12+ hours to ensure the RTSP source is stable.