A sampling system used to digitize the
luminance component (Y) and colour components (R-Y and B-Y) of a
YCbCr component
analog video signal. This is the format often used by consumer
gear.
4:2:0 is essentially equivalent to sampling one line of video at 4:2:2 and the next at 4:0:0 (i.e. luminance only). The bandwidth of the colour signal in 4:2:0 is half that of the luminance.