avidemux
http://fixounet.free.fr/avidemux/
is a multiplatform GPL program that can encode audio and video using ffmpeg...
is available also for windows and macosX
http://fixounet.free.fr/avidemux/

I think it would be easy (not for me) make a filter to create k(s)vcd

what do you think about it?

dunno, but its extremely slow compared to using ffmpeg by itself on the command line...maybe i am doing it wrong?