Indicates the sampling applied to the Y/R-Y/B-Y components of an analog video signal when it is converted into a digital signal. The three numbers indicate the ratio of the sampling rates applied to the individual signals. 4:4:4 indicates that the same sampling rate has been applied to all three signals, 4:2:2 means that the sampling rate of the R-Y and B-Y color difference signals is half that of the luminance signal Y, while 4:1:1 indicates that the sampling rate is one quarter that of the Y signal.