how to get youtube video's format?

hi,all .

I'm playing now with the Youtube API and I began a small project (for fun).

The problem Is the link is http://www.youtube.com/watch?v=j4tpRMfqKsM . maybe its format is mp4,flv,3gp... how can i know what format the video is ?

If someone knows how to do this or if someone could help me find the way to do this, please help me.

NOTE: I'm using php and shell. It will be a web app.

From stackoverflow

• The video format is flv.

  : hi , i know the video is flv . i mean that how can i use php to get the format ?

  Col. Shrapnel : $format = "flv";

  : how do you know that?