Aloha,
GStreamer is a powerful and pretty popular media framework. GNOME already uses it extensively, and KDE just started to. It's based on GLib and uses its object oriented C API style. The objects have names like GstQueue or GstElement.
For similar objects like GtkWindow or GnomeIconList in other libraries, us Gtk2-Perl people tend to directly map them to namespaces: Gtk2::Window and Gnome2::IconList. For smaller libraries like libwnck or librsvg, on the other hand, we try not to pollute the top-level namespace: Gnome2::Wnck::Screen, Gnome2::Rsvg::Handle, etc.
For GStreamer, I would tend towards using Gst as a namespace. It matches the C objects' names. It's short to type, which is not unimportant since it's not like the typical Perl OO module where the full package name only appears once when using the constructor -- the GStreamer bindings contain a lot of objects with their own constructors, many of which almost all programs will use. It's not directly GNOME-related. And lastly, Gst has a precedent: the Python bindings also use this namespace.
On the con side, there's of course the introduction of a new top-level namespace. One that is an abbreviation and not easily recognizable.
So, if you were to write Perl bindings for GStreamer, what namespace would you use?
Multimedia::GStreamer
I don't see any advantage of using Gst over GStreamer as a name, they both describe the same thing and GStreamer is a tad more helpfull (to google a description). Then Gnome part as mentioned seems irrelevant. Glib is possibly usefull info, but probably better conveyed via documentation as an implementation issue. It might be nice to "say" somethnig about what it does: plugin, pipeline... I can't think of a better word.
Multimedia::Pipeline::GStreamer ???
Randy.