This post jumps into using "4:4:4" / "4:2:2" / "4:2:0" notation without seeming to explain what it means. Would be very helpful to add a short explanation!
And that notation is not really intuitive even when you do understand what it means. For example the initial 4 is technically a denominator of other two numbers, but it is not intended to be normalized! A consistent notation would use the reciprocal instead, say, "1-1" for 4:4:4, "2-2" for 4:2:2 and "1-∞" or "1-x" for 4:4:0.
