说明：  常用数字信号处理的C源码:快速傅立叶变换,快速离散正交变换,快速卷积变换,数字滤波,数字图像处理,人工神经网络
(commonly used digital signal processing of C source : fast Fourier transform, fast discrete orthogonal transform, convolution rapid transformation, Digital filtering, digital image processing, artificial neural network)