语音信号子带编码源程序，用matlab做的-voice signal source sub-band coding, using Matlab done

设计了镜像滤波器opt_filter函数来实现子带分解与合成。取N=256， nbands=16，调用滤波器函数完成子带分解与合成-Mirror filters are designed to achieve opt_filter function subband decomposition and synthesis. Take N = 256, nbands = 16, call the filter function and achieve Synthesis Subband Deco