Computation reduction for standard-based video encoders based on the energy preservation property of DCT

Based on the energy preservation property of DCT, an optimization technique for motion estimation (ME), DCT, and quantization for standard-based video encoders is developed. First, a stopping criterion for ME is proposed to reduce the number of checking points in finding the motion vectors, and save the computations. The advantage of introducing such a stopping criterion lies in its adaptability to the quantization parameter and applicability to various fast ME algorithms. Then, the DCT and quantization are jointly optimized by tracing the remaining signal energy and removing unnecessary calculations in the process of DCT and quantization. A pruned 2-D DCT based on Huang's fast DCT algorithm is presented to demonstrate the superiority of this algorithm to the full DCT and an existing all-zero block detection method. Although proved to be computationally efficient, the algorithms introduce no obvious quality loss.