[Mp4-tech] how to compute minimum cost motion vector.

[mayank agarwal]

Hi all,
I am trying to understand the process of motion
estimation in H.264 encoder followed in JM code.
I took first macroblock of first frame and from second
frame i took 4*4 block at 6,5 from first macroblock
and i computed the motion vectors which give the least
SAD in search region of 16*16.
//Motion vector for current block at(6,5)is (9,4) 
//Motion vector for  block at(2,5)is (6,4)// left
//Motion vector for  block at(6,1)is (8,0)// top
//Motion vector for  block at(10,1)is (11,0)//top
right
Now it is mentioned from among these prediction
candiadtes i have to compute the prediction which
yields the minimum cost.
Now my question is if i have to apply the equation 
J=D+LAMBDA*R where D=sum of absolute differences.
how can i compute lambda,is that values directly comes
from the table based on the value of quantization
parameter.
R rate distortion parameter,is
it equal to the number of bits required to encode the
block or it is equal to the difference of candidate
vector and predicted motion vector.
Now my question is:
1. if i am right in my above observations
2.Is the equation J=D+lambda*R(i suppose it is
applicable in taking mode decision i.e to select which
of the prediction modes we have to choose) applicable
here also or there is some other method to compute
determine the minimum cost prediction vector.
3.Can anyone suggest me any docs so that i have a
clear idea of the issues discussed above.
Thanks and Regards,
Mayank 
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