[XviD-devel] somebody can tell me how to use dquant?

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Dear expert:
       Could  anyone tell me how to implement dquant?   how can I use dquant?  If dquant is not equal zero, is current macro's quant equal to previous  macro's  quant add current macro's dquant? dquant is to use to macro level rate control? xvid have not implement macro level rate control,so I don't understand dquant is use in xvid ,it is for future?
Best regard
xiongshu,deng