Crossfade effect with GStreamer?

[All Nicks Are Taken]

I've just started to use Quod Libet, which is a really great jukebox style music player, but it doesn't seem to have a crossfade effect plugin.
I've googled for it, and the only useful thing I found was this link:
http://www.sacredchao.net/quodlibet/ticket/316
The guy there responded him:
"This really needs to be supported easily in GStreamer I'll consider it; one playbin is enough trouble, I don't want to juggle two for a relatively minor feature."
Anyone have an idea what that means? or any idea how can I enable crossfade with that GStreamer?
If it's any help, I'm using Debian Sid and ALSA 1.0.9b.
thanks.