save rtsp stream from live network camera

[konasuresh1571]

I am trying to save live stream from ip camera but file is not created.
my requirement is recording video 20 seconds from live stream. I am using below command but it is not working. please help me.

String[] cmd = {"-y", "-i", "rtsp://username:[email protected]:554", "-c:v", "libx264", "-preset", "ultrafast", "-strict", "-2", "-s", "720*1280", "-aspect", "16:9", file_path };