According to Wikipedia FCC conversion is defined as:

    y = 0.30*r + 0.59*g + 0.11*b
    i = 0.5990*r - 0.2773*g - 0.3217*b
    q = 0.2130*r - 0.5251*g + 0.3121*b

and non-FCC conversion is defined as:

    y = 0.299*r + 0.587*g + 0.114*b
    i = 0.595716*r - 0.274453*g - 0.321263*b
    q = 0.211456*r - 0.522591*g + 0.311135*b

Our current code

    y = 0.30*r + 0.59*g + 0.11*b
    i = 0.60*r - 0.28*g - 0.32*b
    q = 0.21*r - 0.52*g + 0.31*b

looks like FCC conversion with the precision of two decimal places. Actually with this precision the difference between the different conversions are almost absent.