If you’re interested in converting FLV flash videos into more common and portable formats, this is for you. For whatever reason, I couldn’t get ffmpegX (Mac OS X GUI for ffmpeg) to convert an FLV because it would fail with a bunch of errors.

Convert .FLV files into MPEG:

ffmpeg -i flashvideo.flv -ab 64 -ar 22050 -b 800 -s 320x240 video.mpg

You can tweak the switches (i.e. -ab, -ar, -b, -s) to optimize the file size that gets produced. Lower numbers create smaller files but less quality.

I only use the MPEG way method because I haven’t figured out how to install xVid or DivX codecs onto my Mac machine.

Reference How to download and convert YouTube video to MPG/AVI in Ubuntu?