icknay writes "With the upcoming Firefox 3.5 and HTML5 video, there's natural interest in Theora vs. Mpeg-4, but without much evidence either way. Here's clips encoded at various rates to provide concrete comparison between Theora and Mpeg-4. Theora performs decently, but requires more bandwidth than Mpeg-4 (although this is a 1.1alpha release of Theora and Theora has a much better license than Mpeg-4). The quality comparisons are very subjective, but you can try the clips yourself and see how it breaks down. There was an earlier discussion about this, but it lacked much concrete evidence. (Disclosure: it's my page.)"