One of the major challenges of video coding is how to attain the best coding performance under different constraints of computational complexity with various hardware.The computational scalability of coding algorithms is particularly important on this occasion.On the other hand

more and more complicated coding structures are employed to repeatedly applied motion estimation on each block.And the algorithms of motion estimation exerts significant influence on the overall performance of video coding.Therefore

we proposed an optimized motion estimation algorithm with scalable complexity.This algorithm can automatically adapt to different video contents and optimally allocate the computing resources by setting appropriate distortion thresholds.These thresholds are the minimal predicted distortion of each macroblocks plus a unified offset.And all of these thresholds can be computed easily with negligible costs.According to our experiments

our proposed algorithm not only provides scalable complexity

but also achieves better coding performance at the same computational expenses.