tal-reverb-2-juce/src/Engine/HighShelf.h

   1 /*-----------------------------------------------------------------------------
   2
   3 Kunz Patrick 30.04.2007
   4
   5 A one pole low pass filter.
   6
   7 -----------------------------------------------------------------------------*/
   8
   9 #if !defined(__HighShelf_h)
  10 #define __HighShelf_h
  11
  12 #include "Math.h"
  13
  14 class HighShelf
  15 {
  16 public:
  17         int filterDecibel;
  18
  19         float sampleRate;
  20
  21         float a0, a1, a2;
  22         float b0, b1, b2;
  23
  24         float x0, x1, x2;
  25         float     y1, y2;
  26
  27         float outSample;
  28
  29         float a, w0, q, s, alpha;
  30         float cosValue, sqrtValue;
  31         float vsa;   // Very small amount (Denormal Fix)
  32
  33         float dBgain, freq;
  34
  35
  36         HighShelf(float sampleRate, int filterDecibel)
  37         {
  38                 this->sampleRate = sampleRate;
  39                 this->filterDecibel = filterDecibel;
  40
  41                 a0 = a1 = a2 = 0.0f;
  42                 b0 = b1 = b2 = 0.0f;
  43
  44                 x0 = x1 = x2 = 0.0f;
  45                 y1 = y2 = 0.0f;
  46
  47                 q = dBgain = freq = 0.0f;
  48
  49                 s = 2.0f;
  50                 vsa= (1.0f/4294967295.0f);   // Very small amount (Denormal Fix)
  51         }
  52
  53         // gain [0..1], q[0..1], freq[0..44100]
  54         inline void tick(float *inSample, float freq, float q, float gain)
  55         {
  56                 gain = filterDecibel - (1.0f - gain) * filterDecibel * 2.0f;
  57                 calcCoefficients(freq, q, gain);
  58
  59                 outSample = b0*x0 + b1*x1 + b2*x2 - a1*y1 - a2*y2;
  60                 outSample = b0*x0 + b1*x1 + b2*x2 - a1*y1 - a2*y2;
  61                 updateHistory(*inSample, outSample);
  62                 *inSample = outSample;
  63         }
  64
  65         inline void calcCoefficients(float freq, float q, float dBgain)
  66         {
  67                 if (this->q != q || this->dBgain != dBgain || this->freq != freq)
  68                 {
  69                         this->dBgain = dBgain;
  70                         this->q = q;
  71                         this->freq = freq;
  72                         w0 = 2.0f * 3.141592653589793f * freq / sampleRate;
  73                         a = sqrtf(pow(10, dBgain/20.0f));
  74                         alpha = sinf(w0)/(2.0f*q);
  75                         q = 1.0f / sqrt((a + 1.0f/a)*(1.0f/s - 1.0f) + 2.0f);
  76
  77                         cosValue = cosf(w0);
  78                         sqrtValue = sqrtf(a);
  79                 }
  80                 b0 =         a * ((a + 1.0f) + (a - 1.0f) * cosValue + 2.0f * sqrtValue * alpha );
  81                 b1 = -2.0f * a * ((a - 1.0f) + (a + 1.0f) * cosValue                           );
  82                 b2 =         a * ((a + 1.0f) + (a - 1.0f) * cosValue - 2.0f * sqrtValue * alpha );
  83                 a0 =              (a + 1.0f) - (a - 1.0f) * cosValue + 2.0f * sqrtValue * alpha;
  84                 a1 =      2.0f * ((a - 1.0f) - (a + 1.0f) * cosValue                           );
  85                 a2 =              (a + 1.0f) - (a - 1.0f) * cosValue - 2.0f * sqrtValue * alpha;
  86
  87                 a0 = 1.0f/a0;
  88
  89                 b0 *= a0;
  90                 b1 *= a0;
  91                 b2 *= a0;
  92                 a1 *= a0;
  93                 a2 *= a0;
  94         }
  95
  96         inline void updateHistory(float inSample, float outSample)
  97         {
  98                 x0 = saturate(x1, -0.05f);
  99                 x1 = saturate(x2, 0.04f);
 100                 x2 = inSample;
 101
 102                 y2 = y1;
 103                 y1 = outSample;
 104         }
 105
 106         inline float saturate(float x, float variation)
 107         {
 108                 return x - 0.002f * (x + variation) * x * x;
 109         }
 110 };
 111
 112 #endif