towne32 said:

Right, I understand the assumptions. But if it turns out to be true: Is it possible to encode something such that the max bitrate is differently specified for different segments of the same file? Perhaps much fancier encoding software is required (than, say, adobe)? BDInfo spat out the numbers chapter by chapter, and there were no noticeable dips at branching points or in the short m2ts files. But of course if it's only 11 seconds with lower bitrate it would be masked by the average.

I'm mainly asking because if there is indeed a 20mbps max for the entire film, it might actually be preferable to not use branching at all. Assuming one is only creating two versions of Star Wars, for instance, and has no qualms going from BD25 to BD50, a higher bitrate could be used without branching. Obviously, that goes out the window if 3+ branching options, or if the disc was already intended to be a BD50 packed with bonus material. A very inefficient use of space, but it should look better.

Well yes if you were limited to 20Mbps you could just set the 2-hour film to CBR and be done with it (you'd still need branching to fit two versions on though). I suggest testing my theory by trimming 5.825 seconds from the ends of the braching-points of the videos, and then joining all the heads together in one file, and all the tails together in another file and checking the average bitrate. Of course if it's lower than 20Mbps it doesn't prove anything since there's a 68% chance the sample would fall within 1 SDs of the mean, and 95% chance that the sample would fall within 2 SDs of the mean, however if it's higher than 20Mbps it proves the theory wrong (at least for the heads or for the tails of the joining points). And you could continue testing the other discs if it was lower than 20.