media-libs/memphis has a hard dependency on gtk-doc, which in turn pulls severall other potentially unnecessary packages. A brief look into the configure.ac file of the memphis package suggests that the package could be built without gtk-doc support. Please add a "doc" USE flag to media-libs/memphis.
This is not fixable, because gtk-doc is need for the autoreconf step. I am sorry. But it is only a buildtime dep, so it can be removed afterwards.