To convert an avi file to rmvb using mencoder try: mencoder "src.avi" -o "dest.rmvb" -ovc lavc -lavcopts vcodec=mpeg4 -oac mp3lame If real player fails to play generated file, then play it using mplayer. To cut an avi file (5 seconds is the total length to cut), use following command: mencoder -ss 00:10:10 -endpos 00:05:00 -ovc copy -oac copy "src.avi" -o "dest.avi"