Since the latest update gmb is supposed to use gstreamer 1.0 but it seems it still uses gstreamer 0.10, without the option to change this... (see screenshot)
I have glib2, glib-perl and perl-gstreamer installed.
To use gstreamer-1.x you need the perl module Glib::Object::Introspection and the gstreamer introspection data (a file named Gst-1.0.typelib).
On ubuntu these are found in packages libglib-object-introspection-perl and gir1.2-gstreamer-1.0.
You will also need gstreamer-1 itself of course and at least some 1.0 plugins (libgstreamer-plugins-base1.0-0 on ubuntu)
That was fast ;)
I installed "perl-glib-object-introspection" but even though I couldn't find any "gir1.2-gstreamer-1.0" and "Gst-1.0.typelib" package it's working now! Btw I use Arch.
Thanks for Your help!