[MPlayer-users] Re: vbitrate estimation using 3 pass encoding (divx)

Angel angel at knight-industries.com
Mon Jan 6 02:16:08 CET 2003


> i'm still not understand this part.  "that value comes from the length 
> (time) of the movie and free space left after saving the audio on the cd",
> but isn't it also dependent on the fps and size (dimensions) of the movie?

No. It has nothing to do with the dimensions of the movie.
Its a simple equation: 
Target Bitrate = (Size of CD - Size of Audio) / Length of Movie

> i'm drawing this conclusion from the fact when i do a single one time pass 
> encoding of an dvd chapter to divx, if i lower the fps or scale it, the 
> resulting divx is smaller than it would have been if i didn't lower the fps 
> or scale it.

Its possible you scaled the movie down enough that the encoder used the 
minimum quantizer for the entire movie and therefore didn't use the full 
bitrate you specified. Also, if I'm not mistaken the ratecontrol will be more 
accurate using 2 passes because the future quantizers are known.

-Angel



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