The following command combines the png files in the currecn directory (in alphabetical order) at 25 frames a second to make a mpeg movie called my_movie.mpg.

You can change the frame rate by changing the fps= parameter.

You can change the files it uses by changing the *.png to something else. If you want to use a different type of file than png you should also change the type= parameter.

You can change the name of the movie by changing where it says my_movie (but it should always be .mpg unless you change a bunch of other stuff).

mencoder mf://*.png -mf fps=25:type=png -ovc lavc -lavcopts vcodec=mpeg4:mbd=2:trell -oac copy -o my_movie.mpg