405 to 625 conversion

[ppppenguin]

I've done the brightness and contrast, including limiters to prevent digits wrapping round from white to black and vice versa. in "601" black level is 16 and white is 235. 1-15 are available for signals that go a little below black. I've simplified my logic by clipping anything below black. So for example a true PLUGE signal won't be properly reproduced. At the other end I've allowed the full overload range above white.

Calling a day until Monday now. Main thing left to tackle is the interpolator which is definitely unhappy. From what I remember when I did 625 to 405, the interpolator was happy with a wide range of vertical shrink and expand with the same set of coefficients.