installation problem?

I am sorry to ask this but I just don't understand the instructions on the 
Mplayer site for installing FFMpeg. i have installed cvs ffmpeg, mplayer, 
libmp3lame, mencoder, etc...on my Fedora 3, but still have this error 
everytime :
 ffmpeg -i sample.jpeg sample.gif
will return :
 ffmpeg version 0.4.9-pre1, build 4718, Copyright (c) 2000-2004
 Fabrice Bellard built on Feb 20 2006 16:56:48, gcc: 3.4.4 20050721 (Red 
Hat 3.4.4-2)
 test.jpeg : Unknown format

thanks in advance.

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