Old 10-03-2017, 11:13 AM   #1
caseyjames
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Default ReaEQ freq scale

I'm trying to understand the ReaEq frequency parameters curve.

Sampling points in 0.1 increments on the 0.0 -- 1.0 float range I get:

Frequency:
(20, 69.2, 158.9, 322.1, 619.3, 1160.5, 2146.2, 3941.0, 7209.5, 13161.4, 24000)

MIDI pitch:
(15,37,51,64,75,86,96,107,117,128,138)

MIDI pitch difference:
(22,14,13,11,11,10,11,10,11,10)

What is the curve on the low end about? Does anyone have the exact formula?
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Old 10-03-2017, 11:18 AM   #2
Xenakios
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I guess only the Reaper developers know the exact mapping function. If they don't want to reveal that, you could try using more steps to produce a more precise look up table for your purposes.
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Old 10-09-2017, 11:36 AM   #3
Philbo King
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10 or 11 midi notes per divsion = just under 1 octave per division

You might consider doing this with a higher number of FFT points also - the scaling won't change, but the granularity of the scale will (making possible finer increments).
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Old 10-17-2017, 09:48 AM   #4
mpl
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Doesnt these formulas work for you?

https://en.wikipedia.org/wiki/MIDI_tuning_standard:
  • pitch to MIDI
  • MIDI to pitch
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Old 10-29-2017, 11:49 AM   #5
Tale
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Quote:
Originally Posted by caseyjames View Post
Does anyone have the exact formula?
Well, I guess I do now:

Code:
curve = (exp(log(401)*x) - 1) * 0.0025;
freq = (24000 - 20) * curve + 20;
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Old 10-31-2017, 05:23 PM   #6
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Quote:
Originally Posted by Tale View Post
Well, I guess I do now:

Code:
curve = (exp(log(401)*x) - 1) * 0.0025;
freq = (24000 - 20) * curve + 20;
That looks right to me
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