I´m trying to implement the XM format for my player and I have a question about the format.
In the document of Triton, the period for amiga frequence is calculated like this:
Period = (PeriodTab[(Note MOD 12)*8 + FineTune/16]*(1-Frac(FineTune/16)) +
PeriodTab[(Note MOD 12)*8 + FineTune/16]*(Frac(FineTune/16)))
*16/2^(Note DIV 12);
There are some errors in this formula, I think. One is, that I get negative values for PeriodTab when Finetune is negative. Should I take the first value in the PeriodTab then? Is there an easier formula for this perhaps?