To encode one or more (oh yes) files with the given (at the upper text field) command line drop the files at this page. To define the place where in the command line must be filename located, use @FILE_NAME macro. For example, we want to convert some file into the MPEG2. And we have the mymovie.avi file. With the following example, we shall have mymovie.avi.mpg as the output file name:
mencoder @FILE_NAME -ofps 29,970030 -oac copy -ovc lavc -lavcopts vcodec=mpeg2video:vbitrate=3000 -of mpeg -o @FILE_NAME.mpg