NoiseBase.cpp

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/**********************************************************************
 
  Audacity: A Digital Audio Editor
 
  NoiseBase.cpp
 
  Dominic Mazzoni
 
**********************************************************************/
#include "NoiseBase.h"
#include <cmath>
 
const EnumValueSymbol NoiseBase::kTypeStrings[nTypes] = {
   // These are acceptable dual purpose internal/visible names
   /* i18n-hint: not a color, but "white noise" having a uniform spectrum  */
   { XC("White", "noise") },
   /* i18n-hint: not a color, but "pink noise" having a spectrum with more power
    in low frequencies */
   { XC("Pink", "noise") },
   /* i18n-hint: a kind of noise spectrum also known as "red" or "brown" */
   { XC("Brownian", "noise") }
};
 
const EffectParameterMethods& NoiseBase::Parameters() const
{
   static CapturedParameters<NoiseBase, Type, Amp> parameters;
   return parameters;
}
 
//
// NoiseBase
//
 
const ComponentInterfaceSymbol NoiseBase::Symbol { XO("Noise") };
 
NoiseBase::NoiseBase()
{
   Parameters().Reset(*this);
 
   SetLinearEffectFlag(true);
 
   y = z = buf0 = buf1 = buf2 = buf3 = buf4 = buf5 = buf6 = 0;
}
 
NoiseBase::~NoiseBase()
{
}
 
// ComponentInterface implementation
 
ComponentInterfaceSymbol NoiseBase::GetSymbol() const
{
   return Symbol;
}
 
TranslatableString NoiseBase::GetDescription() const
{
   return XO("Generates one of three different types of noise");
}
 
ManualPageID NoiseBase::ManualPage() const
{
   return L"Noise";
}
 
// EffectDefinitionInterface implementation
 
EffectType NoiseBase::GetType() const
{
   return EffectTypeGenerate;
}
 
unsigned NoiseBase::GetAudioOutCount() const
{
   return 1;
}
 
bool NoiseBase::ProcessInitialize(
   EffectSettings&, double sampleRate, ChannelNames)
{
   mSampleRate = sampleRate;
   return true;
}
 
size_t NoiseBase::ProcessBlock(
   EffectSettings&, const float* const*, float* const* outbuf, size_t size)
{
   float* buffer = outbuf[0];
 
   float white;
   float amplitude;
   float div = ((float)RAND_MAX) / 2.0f;
 
   switch (mType)
   {
   default:
   case kWhite: // white
      for (decltype(size) i = 0; i < size; i++)
      {
         buffer[i] = mAmp * ((rand() / div) - 1.0f);
      }
      break;
 
   case kPink: // pink
      // based on Paul Kellet's "instrumentation grade" algorithm.
 
      // 0.129f is an experimental normalization factor.
      amplitude = mAmp * 0.129f;
      for (decltype(size) i = 0; i < size; i++)
      {
         white = (rand() / div) - 1.0f;
         buf0 = 0.99886f * buf0 + 0.0555179f * white;
         buf1 = 0.99332f * buf1 + 0.0750759f * white;
         buf2 = 0.96900f * buf2 + 0.1538520f * white;
         buf3 = 0.86650f * buf3 + 0.3104856f * white;
         buf4 = 0.55000f * buf4 + 0.5329522f * white;
         buf5 = -0.7616f * buf5 - 0.0168980f * white;
         buffer[i] = amplitude * (buf0 + buf1 + buf2 + buf3 + buf4 + buf5 +
                                  buf6 + white * 0.5362);
         buf6 = white * 0.115926;
      }
      break;
 
   case kBrownian: // Brownian
      // float leakage=0.997; // experimental value at 44.1kHz
      // double scaling = 0.05; // experimental value at 44.1kHz
      // min and max protect against instability at extreme sample rates.
      float leakage = ((mSampleRate - 144.0) / mSampleRate < 0.9999) ?
                         (mSampleRate - 144.0) / mSampleRate :
                         0.9999f;
 
      float scaling =
         (9.0 / sqrt(mSampleRate) > 0.01) ? 9.0 / sqrt(mSampleRate) : 0.01f;
 
      for (decltype(size) i = 0; i < size; i++)
      {
         white = (rand() / div) - 1.0f;
         z = leakage * y + white * scaling;
         y = fabs(z) > 1.0 ? leakage * y - white * scaling : z;
         buffer[i] = mAmp * y;
      }
      break;
   }
 
   return size;
}