EN: 4:1:1


Both high definition and standard definition systems where the ratio between luminance and chrominance samples is 4:1 -- one set of color difference samples (R-Y, B-Y) for every four luminance samples (Y). In standard definition video signals it represents luminance (Y) sampling at 13.5 MHz and R-Y/B-Y channel sampling at 3.75 MHz.
Canon USA