说明：  可以读取yuv文件，输入文件夹名字、图像尺寸、帧数等，为处理yuv文件的前提
(Input: filename- YUV sequence file dims- dimensions of the frame [width height] numfrm- number of frames to read startfrm- [optional, default = 0] specifies from which frame to start reading with the convention that the first frame of the sequence is 0- numbered)