from the mplayer man page.
mencoder (MPlayer’s Movie Encoder) is a simple movie encoder, designed
to encode MPlayer-playable movies (see above) to other MPlayer-playable
formats (see below). It encodes to MPEG-4 (DivX/XviD), one of the
libavcodec codecs and PCM/MP3/VBRMP3 audio in 1, 2 or 3 passes. Fur-
thermore it has stream copying abilities, a powerful filter system
(crop, expand, flip, postprocess, rotate, scale, noise, rgb/yuv conver-
sion) and more.
Please
edit your profile to show your location and distribution - I can provide more specific help when I can see these things (see mine: left).