1. A method of motion estimation for video processing, said method comprising steps of: (A) receiving a current block of a video signal comprising a series of frames, wherein each frame comprises a plurality of blocks; (B) determining an optimal residual block having an optimal rate-distortion cost for the current block, further comprising steps of: (1) generating a plurality of residual blocks by performing motion compensation on the current block; (2) generating a plurality of rate-distortion costs for a plurality of generated bitstream segments using a first transform for each of the plurality of residual blocks; (3) selecting the optimal residual block having the optimal rate-distortion cost from the plurality of residual blocks; and (C) transforming said optimal residual block for the purpose of encoding using a second transform, wherein the second transform has a higher complexity than the first transform, said second transform being performed on the optimal residual block in a condition corresponding to the residual block before the first transform is performed on the optimal residual block, and said first and second transforms are associated with two distinct modes in a transform circuit.