Video can not play after downloaded with rtmpdum

Video can not play after downloaded with rtmpdum

 

Hi,
I have a trouble with my downloaded video using rtmpdump command, no video application can read it.
This is my command

rtmpdump.exe -r rtmp://221.132.35.145:38000/live/51/51_1 -o test.flv -v

This is a live video, so I close the cmd window to end of recording the video stream, after that I will receive a "test.flv" file, but it can not run anyway.
Is there something wrong with my rtmp calling function?
Anyone please help me!

Re: Video can not play after downloaded with rtmpdum