[Mp4-tech] h.264 rd costs related

[Bhaskaran Vasudev]

this may be a naive question to many readers of this list.
in h.264 encoding to determine best mode (inter or intra), i have seen 
references to
RD cost (D + lambda R) where D is the distortion calculated after motion 
comp. (reconstructed block).
This means to calculate cost function i have to essentially run a decoding 
loop for each test case.
are there cheaper cost functions that would work (maybe not as effective as 
this one) which do not
involve running a full decoding loop with dct,quant,idct,entropy 
coder,motion compensation etc.
thanks for any and all suggestions.
- vasudev