problem with VirtualDub and DIV4

[Ozymandias]

Hello,

I'm trying to compress an AVI file with the DIV4 codec using VirtualDub, and the data rate of the output file doesn't match at all what I have set in VirtualDub > Video > Compression... > DIV4 Codec > Configure > Data Rate.

example :

original file :
V 981.2 kb/s

compressed with DIV3@910kb/s :
V 942.96 kb/s

compressed with DIV4@910kb/s :
V 494.776 kb/s

Any ideas ?

Thanks,

Ozymandias