there's a new comment on the upstream bug tracker:
"If you use the latest GStreamer core, this should make it possible to seek
whilst the video is being downloaded, even when it's the browser doing the
streaming. Still nowhere near as good as using appsrc, but a nifty hack
Author: Bastien Nocera <email address hidden>
Date: Fri Apr 9 14:56:30 2010 +0100
Split setting up and opening browser streams
Wait until we have the browser stream set up before opening stdin
in the browser, which means we might have a chance to get the stream
With recent GStreamer changes, this means that download buffering would
work, and that we'd get download progress and seeking without needing
to wait until the end of the download.
Helps with https://bugzilla.gnome.org/show_bug.cgi?id=608301"