CaTaClYsM wrote:Well I was backing up a DVD and I was using the XVID guide on Doom9.org (just to see what it was like. I have no real need to.) and a funny thing happened.
The file was about 613 megs (for the audio and video) , the CD's I have are 700. So I decided to try and get the movie a bit bigger to fit the size of the DVD. I did several 2 pass encodes and they never got bigger than 604 megs. Eventually I said 'screw it' and did single pass CBR encodes. Heres the funny part. I did a 6500 7500 8500 and 9000 bitrate encodes all within megabytes of each other. The size increase went from 633 at 6500 to 634 at 9000. Anyone know why that is?
Because the bitrate you set does not have a linear correlation to the final file size. If you were to plot encode size as a function of bitrate for a particular data set, you'd probably find it to loosely resemble an exponential curve that is asymptotic to some encode size. (Note "loosely resemble", as I doubt that the function would be exponential in nature, not knowing enough about the specific transforms involved.)
Most likely, the encoder simply isn't finding any more data to work with, or at least, any more data of consequence.
Filling up 634 / 700 megabytes should be good enough...
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