read these topics about Mencoder
http://forums.buyscripts.in/viewtopic.php?f=4&t=1173
http://forums.buyscripts.in/viewtopic.php?f=11&t=1993
http://forums.buyscripts.in/viewtopic.php?f=3&t=352

and Mencoder_options
http://docs.buyscripts.in/Mencoder_options