<a href="http://weblogs.mozillazine.org/roc/archives/2009/06/directshow_and.html" rel="nofollow">http://weblogs.mozillazine.org/roc/archives/2009/06/directsh...</a><p>Firefox won't use system codecs because they might be insecure, they might be buggy, and Mozilla wants to <i>encourage</i> Web authors to use Theora.