As I said, there’s too many variables for *any* program to accurately predetermine file size. DVDA just happens to be more conservative than most. If your video has a lot of motion between i-frames, then there’s more data that the encoder has to account for than if there are few changes from i-frame to the next i-frame. Even the parameters that you give the encoder will affect the encoded file size. And that’s just the main media. Add to that motion menus, static menus? text-only menus? how many? transition menus? extras file? stop page? second audio track? subtitles? All of these are in the final disc image, and there is simply NO way that a bit-rate calculator can account for all of these variables without actually encoding the file.
That is why it’s called an estimate.
Steve Mann
MannMade Digital Video
http://www.mmdv.com