# What does 0 mean in YUV420

I know whats the difference between various formats such as YUV444,YUV420,YUV422. But what exactly these numbers mean? They are mentioned as chroma subsampling in horizontal and vertical directions. In YUV420 Cb and Cr are sampled at half the resolution of luma in both vertical and horizontal directions. So what does zero in YUV420 mean?

In other words, your 0 says there's no vertical chroma subsampling at all. Instead, you just assume that columns within the four pixel wide subsampling region have identical chroma.