Now a days we often visit a website that display some ad video or some profile video. Most of those are created using camcoders, professional video studio. But those formats are very heavy in Size (storage) to be used on web interface. Therefore as developer you often reach a stage where you need to convert your client supplied video in to other format. For this purpose ffmpeg (http://ffmpeg.mplayerhq.hu/) is best tool. It convert virtually any AVI, MPEG file to any format such as FLV.

ffmpeg can be downloaded from its offical page at http://ffmpeg.mplayerhq.hu/. However, they do not support traditional binary setup. Therefore you need to download complete source either from SVN or a link on their download page. Once your download the source simply run traditional Linux

./configure

make

make install

and your ffmpeg is there for you. It install lots of converter by default and you hardly need to add new codec. I have complied ffmpeg several times on different machine.. it never create any problem for me. Also you can use ffmpeg on windows this article suggest how to install it on Windows, but I never got a chance to try it there.

http://soenkerohde.com/tutorials/ffmpeg/ maybe you find it good.

Here is article that shows how to use ffmpeg to convert AVI to FLV

http://vexxhost.com/blog/2007/05/20/how-to-convertencode-files-to-flv-using-ffmpeg-php/

OR simply use this command
ffmpeg -i clock.avi -ar 22050 -ab 32 -f flv -s 320×240 video.flv

All this is so simply and yet so powerful that it amaze me all time.