[FFmpeg-cvslog] need help to transparent video background

[vishal krishna]

I have a video, in which a object is moving infront of a green curton. I just
need to transparent that green background so that I can embed that video in my
webpage.
I am using window XP and ffmpeg to get it done.
After a lot of googling I found LIBAVFILTER is able to do this, but every one
says write a filter...write a filte.......No one told how to write a filter for
this.

I just need the filter(command) for this which is supported by ffmpeg

ffmpeg -i input.flv -vf "this would be the filter" -y output.mp4