说明：  先对信号进行提升小波分解，然后构造传统小波分解结构[c,l]；接着使用函数ddencmp获取信后压缩阈值，最后采用函数wdencmp实现信后压缩。
(First signal lifting wavelet decomposition, and then construct the traditional wavelet decomposition structure [c, l] then use the function to get the letter ddencmp compression threshold, and finally achieved using the function wdencmp letter after compression.)