Try this one, changed from python deepstream_test2, which merged some deepstream_test3 code for performance issue.
git clone https://github.com/SnapDragonfly/jetson-fpv.git
cd jetson-fpv/utils/deepstream
ln -sf /opt/nvidia/deepstream/deepstream/samples/ samples
cd ../../
python3 ./utils/deepstream/deepstream_NvDCF.py -i rtp://@:5600