signalmath.hh

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 // This Source Code Form is licensed MPL-2.0: http://mozilla.org/MPL/2.0
#pragma once
 
#include <ase/mathutils.hh>
 
namespace Ase {
 
template<typename Float> Float hz_changed (Float a, Float b);
 
template<typename Float> Float voltage2hz (Float x);
 
float fast_voltage2hz (float x);
 
template<typename Float> Float hz2voltage (Float x);
 
float fast_hz2voltage (float x);
 
template<typename Float> Float db_changed (Float a, Float b);
 
template<typename Float> Float voltage2db (Float x);
 
float fast_voltage2db (float x);
 
template<typename Float> Float db2voltage (Float x);
 
float fast_db2voltage (float x);
 
template<typename Float> Float voltage_changed (Float a, Float b);
 
struct Logscale {
  double b2 = 0;         // log2 (begin)
  double r2 = 1, ir = 1; // range
  void
  setup (double min, double max)
  {
    b2 = ::log2l (min);
    auto range = ::log2l (max) - b2;
    ir = 1.0 / range;
    r2 = range;
  }
  double
  scale (double normalized) const
  {
    return ::exp2 (b2 + normalized * r2);
  }
  double
  iscale (double mmvalue) const
  {
    return (::log2 (mmvalue) - b2) * ir;
  }
};
 
// == Implementations ==
static constexpr const long double c3_hertz = 261.6255653005986346778499935233; // 440 * 2^(-9/12)
static constexpr const long double c3_hertz_inv = 0.0038222564329714297410505703465146; // 1 / c3_hertz
 
template<typename Float> extern inline ASE_CONST Float
voltage2hz (Float x)
{
  return std::exp2 (x * Float (10.0)) * Float (c3_hertz);
}
 
extern inline ASE_CONST float
fast_voltage2hz (float x)
{
  return fast_exp2 (x * 10.0f) * float (c3_hertz);
}
 
template<typename Float> extern inline ASE_CONST Float
hz2voltage (Float x)
{
  return std::log2 (x * Float (c3_hertz_inv)) * Float (0.1);
}
 
extern inline ASE_CONST float
fast_hz2voltage (float x)
{
  return fast_log2 (x * float (c3_hertz_inv)) * 0.1f;
}
 
template<typename Float> extern inline ASE_CONST Float
voltage2db (Float x)
{
  return std::log10 (std::abs (x)) * Float (20);
}
 
extern inline ASE_CONST float
fast_voltage2db (float x)
{
  return fast_log2 (__builtin_fabsf (x)) * 6.02059991327962390427477789448986f;
}
 
template<typename Float> extern inline ASE_CONST Float
db2voltage (Float x)
{
  return std::pow (10, x * Float (0.05));
}
 
extern inline ASE_CONST float
fast_db2voltage (float x)
{
  return fast_exp2 (x * 0.1660964047443681173935159714744695f);
}
 
template<typename Float> extern inline ASE_CONST Float
hz_changed (Float a, Float b)
{
  return __builtin_fabsf (a - b) > 1e-3;
}
 
template<typename Float> extern inline ASE_CONST Float
db_changed (Float a, Float b)
{
  return __builtin_fabsf (a - b) > 1e-3;
}
 
template<typename Float> extern inline ASE_CONST Float
voltage_changed (Float a, Float b)
{
  return __builtin_fabsf (a - b) > 1e-7;
}
 
} // Ase