Abstract: A novel Discrete Cosine Transform（DCT-II） based algorithm for fast computation of the Modulated Complex Lapped Transform（MCLT） with any windows function is presented.For the MCLT of length-2M input data sequence，the proposed algorithm is based on two stages of butterfly operations and two DCT-II of length-M.The proposed algorithm involves M/2 zero points separately，thus it reduces the storage need of the hardware and decreases the computation complexity.For a length-M MCLT，the proposed algorithm requires only O（MlbM） multiplication for Sine window function and O（MlbM+2M） multiplication for any other window function.Experimental results also show that this method can reduce real computation time by 2% compared with Malvar’s algorithm.

Key words: Modulated Complex Lapped Transform（MCLT）, Discrete Cosine Transform（DCT）, Window function, fast algorithm

摘要： 提出了一种基本计算单元为DCT-II变换的MCLT快速算法。它将基于任意窗函数的MCLT系数的实部和虚部分别映射为一半输入序列为0的DCT-II变换。对于M点的MCLT变换，该算法只需计算两个一半输入序列为0的M点DCT-II变换和两组蝶形运算。对M点的MCLT，当窗函数为正弦窗时，提出快速算法的运算复杂度为O（MlbM）;当窗函数为任意窗时，其运算复杂度为O（MlbM+2M）。实验结果表明：相对于已有的快速算法，由于该算法的中间处理过程中，一半输入序列为0，其实际计算时间减少2%以上。该算法降低了软硬件实现的存储复杂度，更符合实际应用要求。

关键词: 复数调制重叠变换（MCLT）, 离散余弦变换（DCT）, 窗函数, 快速算法