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added idecibel and moved decibel helpers to decibel.hh

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Ahmet Inan 2019-02-27 10:25:50 +01:00
commit f1891d97a8
3 changed files with 48 additions and 27 deletions
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5
README.md
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@ -122,7 +122,10 @@ Some everyday helpers:
* [probability density function](https://en.wikipedia.org/wiki/Probability_density_function) of the [normal distribution](https://en.wikipedia.org/wiki/Normal_distribution)
* [sinc function](https://en.wikipedia.org/wiki/Sinc_function)
* [delta function](https://en.wikipedia.org/wiki/Dirac_delta_function)
* [decibel function](https://en.wikipedia.org/wiki/Decibel)
### [decibel.hh](decibel.hh)
[Decibel](https://en.wikipedia.org/wiki/Decibel) calculation helpers.
### [resampler.hh](resampler.hh)

44
decibel.hh Normal file
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@ -0,0 +1,44 @@
/*
Decibel calculation helpers
Copyright 2018 Ahmet Inan <inan@aicodix.de>
*/
#pragma once
namespace DSP {
template <typename TYPE>
TYPE decibel(TYPE v)
{
#if 0
return TYPE(10) * log10(v);
#else
static constexpr TYPE
// 2*1024*10/l(10)
scale = 8894.350989378597430295120259412072085389250678859091274024013479236L,
inv1 = TYPE(1) / TYPE(1),
inv3 = TYPE(1) / TYPE(3),
inv5 = TYPE(1) / TYPE(5),
inv7 = TYPE(1) / TYPE(7),
inv9 = TYPE(1) / TYPE(9),
inv11 = TYPE(1) / TYPE(11),
inv13 = TYPE(1) / TYPE(13);
TYPE x = v;
for (int i = 0; i < 10; ++i)
x = sqrt(x);
x = (x - TYPE(1)) / (x + TYPE(1));
TYPE xx = x * x;
return scale * x * (xx * (xx * (xx * (xx * (xx * (xx *
inv13 + inv11) + inv9) + inv7) + inv5) + inv3) + inv1);
#endif
}
template <typename TYPE>
TYPE idecibel(TYPE dB)
{
return pow(TYPE(10), dB / TYPE(10));
}
}

26
utils.hh
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@ -40,31 +40,5 @@ TYPE delta(TYPE x)
return TYPE(0) == x ? TYPE(1) : TYPE(0);
}
template <typename TYPE>
TYPE decibel(TYPE v)
{
#if 0
return TYPE(10) * log10(v);
#else
static constexpr TYPE
// 2*1024*10/l(10)
scale = 8894.350989378597430295120259412072085389250678859091274024013479236L,
inv1 = TYPE(1) / TYPE(1),
inv3 = TYPE(1) / TYPE(3),
inv5 = TYPE(1) / TYPE(5),
inv7 = TYPE(1) / TYPE(7),
inv9 = TYPE(1) / TYPE(9),
inv11 = TYPE(1) / TYPE(11),
inv13 = TYPE(1) / TYPE(13);
TYPE x = v;
for (int i = 0; i < 10; ++i)
x = sqrt(x);
x = (x - TYPE(1)) / (x + TYPE(1));
TYPE xx = x * x;
return scale * x * (xx * (xx * (xx * (xx * (xx * (xx *
inv13 + inv11) + inv9) + inv7) + inv5) + inv3) + inv1);
#endif
}
}