This is more of a technical curiosity than anything else, but every web site that I visit gives me a definition for "variable bit rate". Well, DUH! Could it possibly mean that "variable" means "changing"? Imagine that. I'm starting to play with variable bit rates now that (from what I understand) DVDit PE has better chapter support for variable bit rate MPEG-2 files, so I'd like to take advantage of that. But I'm just curious about it because I still need to set a bit rate when creating the MPEG-2 file. What's the purpose of this setting? Maximum bit rate? Average? Optimal? How does the encoder determine the best per-frame bit rate based on this number? Again, just technical curiosity, but most web sites that I've seen give me the vanilla definition that I already know.