Youtube flash videos to DivX (on Linux)

This how I convert flash I usually use Firefox VideoHelper Addon to download youtube videos. To play them on my Philips DVP5986K DVD player from USB drive, I need to convert it to DivX.

mencoder /home/shon/Desktop/file-864260998.flv -ovc lavc -oac mp3lame -ffourcc DX50 -o out.avi