I'm considering first convert it to AVI, then convert it to real media but converting avi take too much time and space, besides, real media is not open source
I've never attempted to do a reencode of an already existing vcd but my guess is that
either ffmpeg or mencoder would be able to do it. I mostly convert avi's to dvd's though, and I use tovid (tovid.sourceforge.net) to do it. tovid from the command line would also be
a wrapper to try the conversion with.