说明：  小波包分解（wavelet packet decomposition）也可称为小波包（wavelet packet）或子带树（subband tree）及最佳子带树结构（optimal subband tree structuring）。其概念是用分析树来表示小波包，即利用多次叠代的小波转换分析输入讯号的细节部分。本案例主要用于小波包分解计算及绘图
(The wavelet packet decomposition can also be called the wavelet packet or the subband tree and the best subband tree structure. The concept is to use the analysis tree to represent the wavelet packet, that is, to analyze the details of the input signal by the multiple iterative wavelet transform. This case is mainly used in the calculation and drawing of wavelet packet decomposition)