中文摘要：

改进了一种DCT快速算法，使之可用于降低H．264中整数4×4DCT的复杂度．考虑到Laplaeian模型不能准确地描述实际的H．264DCT系数的分布，定义了3类简化块，并用统计分析的方法分别建立了这3类块的系数分布模型，进而提出了一种基于新模型的快速DCT算法．设计了简化块的蝶形算法，并分析、比较了所提出的2种快速DCT算法的复杂度．以后者为基础，设计了一种DCT复杂度可分级机制，以调节不同计算能力平台上的4×4DCT的复杂度．实验结果表明，该算法能够准确地按照设定目标控制DCT复杂度，且保证编码性能．

英文摘要：

An improved fast DCT algorithm is set up to reduce the complexity of H.264 integer 4 × 4 DCT. Since the 4 × 4 DCT distribution does not fit Laplacian model well, three simplified blocks are defined and accordingly three coefficient models are created based on a statistical analysis. Furthermore, a fast DCT algorithm based on new models is proposed. Three butterfly algorithms are designed for those 3 simplified blocks respectively, and the complexities of the proposed algorithms are analyzed and compared. Then, a complexity scalable algorithm based on the latter is presented to adjust the 4 ×4 DCT complexity on different platforms with limited computation resource. Simulation results show that the algorithm can control H. 264 4 ×4 DCT complexity within the target with negligible loss of encoding performance.