DVD-RB with CCE . Why low VBR_Bias value?

vbimport

#1

Can someone explain to me why everyone who uses CCE SP trial has low values in the VBR_BIAS field ?
I hear values like 20 or 25 while DVD-RB accepts values up to 100.
Why doesn’t someone use a value of 50 for example ?


#2

Taken from doom9

VBR_Bias controls how CCE distributes the bitrate. During the first CCE pass, the bitrate is distributed to achieve constant quality. The bias determines how much weight is given towards keeping that allocation. High values prevent high bitrate fluctuations in between GOPs, and low values give CCE more freedom to use bits in highly demanding areas.
Higher is not always better:)


#3

I know what VBR_BIAS is doing .
But I’ve made a copy (for testing purposes) of my CONTACT R2 disc with VBR_BIAS set to 25 and in some scenes the bitrate was very low (about 2.2) and the picture quality was lowered too.
In the original disc , in the same scene the bitrate was about 6.0 . The copy was movie-only with one subtitle and the whole “compression” level was only 10% of the original.
Any suggestions ?


#4

Of course there were other scenes where the difference of the bitrate from the original to the copy was not that big but I wish I could find a setting wich doesn’t make some scenes to seem “poor” of quality .


#5

I apologise for my stagnant answer earlier. VBR Bias can be a tough one to get right, VBR is dependant on the movie in question, and ‘compression’ required, so to speak. Using a higher Bias will result in a more CBR style finish, call it Constant quality.

All I could suggest is play around with it, the only discouraging factor of this will be the mass of time it may take. Maybe start at 50 and decrease in increments of 10 til your happy with the result, people will tell you this setting and that, but its what your happy with. And because your talking CCE SP, be sure to do 4 passes with a lower bias.


#6

Thanks a lot :smiley: