I hadn't thought of replacing Gnome apps with KDE apps. But that
sounds like a good idea. I'm going to give that a try.

As for the app I was using, it was the "Totem Movie Player" that came
with the installation. I had installed the ¨Ubuntu restricted extras¨
and Totem seems to be the app for all the codecs weather running solo
or within Firefox. I may try replacing it with MPlayer and its' Gnome
frontend.