将高清1920x1080YUV视频序列按2：1比例下采样-The high-definition video sequences 1920x1080YUV downsampling ratio of 2:1

Read a grayscale image, downsample it by a factor of 4, and reconstruct the full size image the downsampled image. Then, prefilter the original image with a lowpass filter and repeat downsampling and reconstruction as before. -Read a grayscale im