Embodiments of the present specification provide a method for constructing a
processing circuit for a target transform. The target transform is a
discrete transform or its inverse transform that transforms an input coefficient sequence into an output coefficient sequence based on a
rotation factor. The method includes, for a K-point input coefficient sequence to be processed, determining a plurality of candidate
decomposition points corresponding to a k-bit coefficient index. Then, starting from a low-bit
decomposition point, for each candidate
decomposition point, determining the minimum storage cost under each candidate decomposition point according to a decomposition
cost evaluation function through recursive index bit number decomposition for several levels, so as to determine a target decomposition mode of the k-bit coefficient index with the minimum storage cost. The decomposition
cost evaluation function limits the storage cost to include the cost of a (n-p)th order first transform, the cost of a pth order second transform, and the local cost for inter-level
rotation factor multiplication. According to the target decomposition mode, a corresponding memory for the
rotation factor is allocated to form a
processing circuit.