AsyncAudioCompressor.h

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#ifndef ASYNC_AUDIO_COMPRESSOR_INCLUDED
#define ASYNC_AUDIO_COMPRESSOR_INCLUDED
 
 
/****************************************************************************
 *
 * System Includes
 *
 ****************************************************************************/
 
#include <cmath>
 
 
/****************************************************************************
 *
 * Project Includes
 *
 ****************************************************************************/
 
#include <AsyncAudioProcessor.h>
 
 
 
/****************************************************************************
 *
 * Local Includes
 *
 ****************************************************************************/
 
 
 
/****************************************************************************
 *
 * Forward declarations
 *
 ****************************************************************************/
 
 
 
/****************************************************************************
 *
 * Namespace
 *
 ****************************************************************************/
 
namespace Async
{
 
 
/****************************************************************************
 *
 * Forward declarations of classes inside of the declared namespace
 *
 ****************************************************************************/
 
  
 
/****************************************************************************
 *
 * Defines & typedefs
 *
 ****************************************************************************/
 
 
 
/****************************************************************************
 *
 * Exported Global Variables
 *
 ****************************************************************************/
 
 
 
/****************************************************************************
 *
 * Class definitions
 *
 ****************************************************************************/
 
class EnvelopeDetector
{
  public:
    EnvelopeDetector( double ms = 1.0, double sampleRate = INTERNAL_SAMPLE_RATE )
      : sampleRate_( sampleRate ), ms_( ms ), coef_( 0.0 )
    {
      setCoef();
    }
 
    virtual ~EnvelopeDetector() {}
 
    // time constant
    virtual void   setTc( double ms )
    {
      ms_ = ms;
      setCoef();
    }
 
    virtual double getTc( void ) { return ms_; }
 
    // sample rate
    virtual void   setSampleRate( double sampleRate )
    {
      sampleRate_ = sampleRate;
      setCoef();
    }
 
    virtual double getSampleRate( void ) { return sampleRate_; }
 
    // runtime function
    inline void run( double in, double &state )
    {
      state = in + coef_ * ( state - in );
    }
 
  private:
    double sampleRate_;         // sample rate
    double ms_;                 // time constant in ms
    double coef_;               // runtime coefficient
    
    void setCoef( void )        // coef algorithm
    {
      coef_ = exp( -1.0 / ( 0.001 * ms_ * sampleRate_ ) );
    }
 
}; // end EnvelopeDetector class
 
 
 
 
 
class AudioCompressor : public AudioProcessor
{
  public:
    AudioCompressor(void);
  
    ~AudioCompressor(void);
  
    void setThreshold(double thresh_db) { threshdB_ = thresh_db; }
  
    void setRatio(double ratio) { ratio_ = ratio; }
  
    void setAttack(double attack_ms) { att_.setTc(attack_ms);}
  
    void setDecay(double decay_ms) { rel_.setTc(decay_ms); }
  
    void setOutputGain(float gain);
  
    void reset(void);
 
    
  protected:
    virtual void processSamples(float *dest, const float *src, int count);
    
    
  private:
    // transfer function
    double threshdB_;   // threshold (dB)
    double ratio_;              // ratio (compression: < 1 ; expansion: > 1)
    double output_gain;
 
    // attack/release
    EnvelopeDetector att_;      // attack
    EnvelopeDetector rel_;      // release
 
    // runtime variables
    double envdB_;                      // over-threshold envelope (dB)
    
    AudioCompressor(const AudioCompressor&);
    AudioCompressor& operator=(const AudioCompressor&);
    
};  /* class AudioCompressor */
 
 
} /* namespace */
 
#endif /* ASYNC_AUDIO_COMPRESSOR_INCLUDED */
 
 
 
/*
 * This file has not been truncated
 */