Usually, you apply

[R]    [ 1     0        1.402   ][Y]
[G] =  [ 1  -0.34414   -0.71414 ][U]
[B]    [ 1    1.772     0       ][V]


after unlevelshifting U and V (subtracting 128 from them).

This matrix multiplication may give results out of RGB space, so you
have to clamp the resulting bytes to [0..255].
The conversion should be done with arbitrary big integers, not floats :)

This applies to YUV data whereas NTSC may have YIQ where a 33 degree
rotation to U/V is buid in.

