rate control in MPEG

Hi all,

Iam currently working on the implementation of Simple Profile MPEG-4
codec on OMAP 2420. According to anexure L i.e. rate control, we need
to know the MAD values of each macroblock of the current frame prior
to encoding so as to decide the target bits and quantization parameter
for all the macroblocks of current frame.

But with the architecture of OMAP 2420 so as to maintain the
concurrency among various coprocessors (iMX,VLCD,..) I have to take
the MAD value of a MB during its encoding and not prior to encoding.
Can anybody help me in devicing a method to predict the MAD value of
the MB's of current VOP .
Any pointers??

Thank You all.

Pankaj Darak.