4:2:2

Defines standard definition video signals, where the luminance (Y) is sampled at 13.5 MHz and the color difference samples (R-Y,B-Y) channels are each sampled at 6.75 MHz. This terminology has come into common usage to describe both high definition and standard definition systems where the ratio between luminance and chrominance samples is 2 to 1 (i.e. 2 sets of color difference samples (R-Y,B-Y) for every 4 luminance samples (Y)). Also see 22:11:11