Assume that you have a movie in flash video but you want to convert it to another format, say mpg, to be able to play on more devices. On Ubuntu/Debian this is quite easy to achieve. Start with installing the necessary packages (two steps in order to decrease line length).

sudo aptitude install libavcodec-unstripped-52 libavdevice-unstripped-52 libavformat-unstripped-52 
sudo aptitude install libavutil-unstripped-49 libpostproc-unstripped-51 libswscale-unstripped-0 ffmpeg 

So to convert just run:

ffmpeg -i movie.flv -target dvd -aspect 16:9 movie.mpg

There are other target formats to choose from if needed.

// John