ffmpeg to get screenshot

I have a collections of videos, and I would like to get a screenshot from every on of them, and save them all in a folder.

I was told about ffmpeg, a Linux command. But the only extension I get is mpg, instead of .jpeg or .png.

Anybod开发者_Python百科y could tell me if it is possible to write something similar to:

ffmpeg -i videoscambiados/"+filename+".flv img/"+filename+".png

instead of this?

ffmpeg -i videoscambiados/"+filename+".flv img/"+filename+".mpg

This piece of code is got from a java program I made, and filename, of course, is the name of every videos I have in /videoscambiados and I would like to save the images in /img

Thanks in advance!

ffmpeg -i videoscambiados/" +filename+ ".flv -r 1 -ss 00:00:10 -t 1 -s 146x110 img/" +filename+ ".jpg