Define Chroma subsampling

Chroma subsampling

Chroma subsampling is a type of compression that reduces the color information in a data in favor of luminance data. This reduces the bandwidth without significantly affecting the existing picture quality.

Chroma subsampling 4:4:4 vs 4:2:2 vs 4:2:0 meaning

The first number refers to the size of the sample. Then the two following numbers both refer to chroma. They are both relative to the first number and define the horizontal and vertical sampling respectively.

A signal with chroma 4:4:4 has no compression (so it is not sub-sampled) and transports both luminance and color data entirely. In a four by two array of pixels, 4:2:2 has half the chroma of 4:4:4, and 4:2:0 has a quarter of the color information available.

The chroma 4:2:2 signal will have half the sampling rate horizontally, but will maintain full sampling vertically. And chroma 4:2:0, on the other hand, will only sample colors out of half the pixels on the first row and ignores the second row of the sample completely.