al_Crossover.hpp

#ifndef INCLUDE_AL_CROSSOVER_HPP
#define INCLUDE_AL_CROSSOVER_HPP
 
/*  Allocore --
        Multimedia / virtual environment application class library
 
   Copyright (C) 2009. AlloSphere Research Group, Media Arts & Technology, UCSB.
   Copyright (C) 2012. The Regents of the University of California. All
   rights reserved.
 
   Redistribution and use in source and binary forms, with or without
   modification, are permitted provided that the following conditions are
   met:
 
   Redistributions of source code must retain the above copyright
   notice, this list of conditions and the following disclaimer.
 
   Redistributions in binary form must reproduce the above
   copyright notice, this list of conditions and the following disclaimer in the
   documentation and/or other materials provided with the
   distribution.
 
   Neither the name of the University of California nor the names
   of its contributors may be used to endorse or promote products derived from
   this software without specific prior written permission.
 
   THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS
   IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
   IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
   PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR
   CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
   EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
   PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS;
   OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
   WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR
   OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF
   ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 
 
        File description:
        CrossOver: a cross-over shelf filter that sums to an allpass
        (Useful for mixing different Ambisonic encoding flavors)
 
        File author(s):
        Graham Wakefield, 2010, grrrwaaa@gmail.com
*/
 
#include <float.h>
#include <stdio.h>
 
#include "al/math/al_Constants.hpp"
 
namespace al {
 
template <typename T = double> class Crossover {
public:
  void freq(T f, T fs);
 
  Crossover(T f = (T)600, T fs = (T)44100.) {
    freq(f, fs);
    clear();
  }
 
  void next(const T in, T *lo, T *hi);
 
  void clear() {
    mZ0 = (T)0;
    mZ1 = (T)0;
    mZ2 = (T)0;
  }
 
protected:
  // coefficients and history
  T mC0, mC1, mZ0, mZ1, mZ2;
};
 
template <> void Crossover<double>::freq(double f, double fs) {
  double rad = M_PI * 2. * f / fs;
  double cosine = cos(rad);
  double sine = sin(rad);
  if (abs(c) > 0.0001) {
    mC0 = (sine - 1.) / cosine;
  } else {
    mC0 = cosine * 0.5;
  }
  mC1 = (1. + mC0) * 0.5;
}
 
template <>
inline void Crossover<double>::next(const double in, double *lo, double *hi) {
  static const double denorm_offset = DBL_EPSILON * 2.;
 
  const double v0 = in - mC0 * mZ0;
  const double x0 = mZ0 + mC0 * v0;
 
  const double v1 = mC1 * (in - mZ1);
  const double x1 = v1 + mZ1;
 
  const double v2 = mC1 * (x1 - mZ2);
  const double x2 = v2 + mZ2;
 
  mZ0 = v0 + denorm_offset;
  mZ1 = v1 + x1 + denorm_offset;
  mZ2 = v2 + x2 + denorm_offset;
 
  *lo = x2;
  *hi = x0 - x2;
}
 
template <> void Crossover<float>::freq(float f, float fs) {
  float rad = M_PI * 2.f * f / fs;
  float cosine = cosf(rad);
  float sine = sinf(rad);
  if (fabs(cosine) > 0.0001f) {
    mC0 = (sine - 1.f) / cosine;
  } else {
    mC0 = cosine * 0.5f;
  }
  mC1 = (1.f + mC0) * 0.5f;
}
 
template <>
inline void Crossover<float>::next(const float in, float *lo, float *hi) {
  static const float denorm_offset = FLT_EPSILON * 2.;
 
  const float v0 = in - mC0 * mZ0;
  const float x0 = mZ0 + mC0 * v0;
 
  const float v1 = mC1 * (in - mZ1);
  const float x1 = v1 + mZ1;
 
  const float v2 = mC1 * (x1 - mZ2);
  const float x2 = v2 + mZ2;
 
  mZ0 = v0 + denorm_offset;
  mZ1 = v1 + x1 + denorm_offset;
  mZ2 = v2 + x2 + denorm_offset;
 
  *lo = x2;
  *hi = x0 - x2;
}
 
} // namespace al
#endif