quartz: add implementations for AmpFactorToDB and DBToAmpFactor
reif at earthlink.net
Tue Jan 2 14:33:20 CST 2007
Roderick Colenbrander wrote:
>Why are you using a lookup table and not just a log10(x) and 10^(x) for the gain <-> dB conversions? That's how it should be done I think like 10x corresponding to 20dB (assuming signal gain). In your tests it is just:
>2000*log10(gain) - 9630 for going to that dB-like scale.
That was the only way to get the exact same results as a native dll.
For whatever reason Microsoft decided not to use the standard equations
like the rest of the world. I assume it was to eliminate the need for
floating point calculations. Actually you could use the same equation
that the generated the table to go from dB to amp but you can't use an
equation to go the other way around because of the weird roundoff errors
that result from using a lookup table.
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