small question regarding instalation via ymp

This may seam a silly question but I am kind on new in the linux word. I am using openSuse 11 with both gnome and kde (just to have them both). Most of the time I am using Gnome but KDE is good to be around. I installed compiz as well via the ymp quick installers. Here comes the question.
There are always 2 installers one for kde and one for gnome. If I install the gnome one (because I use gnome) do I have to install the kde one as well to have compiz in kde to, or the gnome one is all I need. The same question when I tried to install codecs and stuff via the installers on this page Multimedia - openSUSE-Community
So my question is: do I have to install the gnome and kde ymps to have codecs in gnome and kde or one installer is sufficient. Why do we need installers for both interfaces…for me is a nonsense, I an waiting for an answer please!

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