create a new virtual environment
python -m venv <virtual-environment-name>
activate a virtual environment
source <virtual-env-path>/bin/activate
on the Raspberry Pi
raspivid -w 640 -h 480 --nopreview -t 0 -o - | nc 192.168.1.32 5001
on the client (Mac Os in my case)
nc -l 5001 | mplayer -fps 30 -demuxer h264es -