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

   1 /*
   2         ==============================================================================
   3         This file is part of Tal-Reverb by Patrick Kunz.
   4
   5         Copyright(c) 2005-2009 Patrick Kunz, TAL
   6         Togu Audio Line, Inc.
   7         http://kunz.corrupt.ch
   8
   9         This file may be licensed under the terms of of the
  10         GNU General Public License Version 2 (the ``GPL'').
  11
  12         Software distributed under the License is distributed
  13         on an ``AS IS'' basis, WITHOUT WARRANTY OF ANY KIND, either
  14         express or implied. See the GPL for the specific language
  15         governing rights and limitations.
  16
  17         You should have received a copy of the GPL along with this
  18         program. If not, go to http://www.gnu.org/licenses/gpl.html
  19         or write to the Free Software Foundation, Inc.,
  20         51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
  21         ==============================================================================
  22  */
  23
  24
  25 #if !defined(__AllPassFilter_h)
  26 #define __AllPassFilter_h
  27
  28 #include "Math.h"
  29 #include "AudioUtils.h"
  30
  31 class AllPassFilter
  32 {
  33 private:
  34         float delay, gain;
  35         float* buffer;
  36         int bufferLength, writePtr, readPtr1, readPtr2;
  37         float z1;
  38
  39         AudioUtils audioUtils;
  40
  41 public:
  42         // delay times in milliseconds
  43         AllPassFilter(float delayTime, float feedbackGain, long samplingRate)
  44         {
  45                 //OutputDebugString("start init allPass");
  46                 gain = feedbackGain;
  47                 delay = delayTime;
  48
  49                 bufferLength = (int)(delay * samplingRate / 1000.0f);
  50                 bufferLength = audioUtils.getNextNearPrime(bufferLength);
  51                 buffer = new float[bufferLength];
  52
  53                 //zero out the buffer (create silence)
  54                 for (int i = 0; i < bufferLength; i++)
  55                         buffer[i] = 0.0f;
  56
  57                 writePtr = readPtr1 = readPtr2 = 0;
  58                 z1 = 0.0f;
  59                 //OutputDebugString("end init allPass");
  60         }
  61
  62         ~AllPassFilter()
  63         {
  64                 delete buffer;
  65         }
  66
  67         // all values [0..1]
  68         inline float processInterpolated(float input, float delayLength, float diffuse, bool negative)
  69         {
  70                 // dynamic interpolated
  71                 float offset = (bufferLength - 2.0f) * delayLength + 1.0f;
  72                 readPtr1 = writePtr - (int)floorf(offset);
  73
  74                 if (readPtr1 < 0)
  75                         readPtr1 += bufferLength;
  76
  77                 readPtr2 = readPtr1 - 1;
  78                 if (readPtr2 < 0)
  79                         readPtr2 += bufferLength;
  80
  81                 // interpolate, see paper: http://www.stanford.edu/~dattorro/EffectDesignPart2.pdf
  82                 float frac = offset - (int)floorf(offset);
  83                 float temp = buffer[readPtr2] + buffer[readPtr1] * (1-frac) - (1-frac) * z1;
  84                 z1 = temp;
  85
  86                 float output;
  87                 if (!negative)
  88                 {
  89                         buffer[writePtr] = diffuse * gain * temp + input;
  90                         output = temp - diffuse * gain * buffer[writePtr];
  91                 }
  92                 else
  93                 {
  94                         buffer[writePtr] = diffuse * gain * temp - input;
  95                         output = temp + diffuse * gain * buffer[writePtr];
  96                 }
  97
  98                 if (++writePtr >= bufferLength)
  99                         writePtr = 0;
 100
 101                 return output;
 102         }
 103
 104         inline float process(float input, float diffuse)
 105         {
 106                 float temp = buffer[readPtr1];
 107                 buffer[readPtr1] = diffuse * gain * temp + input;
 108                 float output = temp - diffuse * gain * buffer[readPtr1];
 109
 110                 if (++readPtr1 >= bufferLength)
 111                         readPtr1 = 0;
 112
 113                 return output;
 114         }
 115
 116         inline float process(float input)
 117         {
 118                 float temp = buffer[readPtr1];
 119                 buffer[readPtr1] = gain * temp + input;
 120                 float output = temp - gain * buffer[readPtr1];
 121
 122                 if (++readPtr1 >= bufferLength)
 123                         readPtr1 = 0;
 124
 125                 return output;
 126         }
 127 };
 128 #endif