YUV420

YUV420 is a common color subsampling scheme used in video and image compression. It's a member of the YUV family of color spaces, which represent color information by separating the luminance (brightness) component, Y, from the chrominance (color) components, U and V. This separation is beneficial because the human eye is more sensitive to changes in brightness than to changes in color.

In YUV420, the luminance component (Y) is sampled at full resolution. However, the chrominance components (U and V) are subsampled. The "420" designation indicates the sampling ratio. The first '4' means that for every four luminance samples, there are four luminance samples in the horizontal direction (full resolution). The first '2' means that for every two luminance samples horizontally, there is one U sample and one V sample. The second '0' means that for every two luminance samples vertically, there is one U sample and one V sample. In essence, the U and V information is stored at one-quarter the resolution of the Y information. This reduction in color information significantly reduces the data required to represent an image or video, making it more efficient for storage and transmission. YUV420 is widely used in digital television broadcasting, video streaming, and various video file formats like MP4 and AVI.