/*

 Copyright (C) 2016 Apple Inc. All Rights Reserved.

 See LICENSE.txt for this sample’s licensing information

 Abstract:

 An object to calculate running average RMS power and peak of an audio stream

*/

#ifndef __PowerMeter

#define __PowerMeter

#include <CoreAudio/CoreAudioTypes.h>

#include <math.h>

const double kMinLinearPower = 1e-6;

const double kMinDecibelsPower = -120.0;

const double kMaxDecibelsPower = 20.0;

const double kLog001 = -6.907755278982137; // natural log of 0.001 (0.001 is -60 dB)

inline double CalcDecayConstant(double in60dBDecayTimeInSeconds, double inSampleRate)

{

    double denominator = in60dBDecayTimeInSeconds * inSampleRate;

    if (denominator < 1e-5) return 0.;

    return exp(kLog001 / denominator);

}

inline double AmpToDb(double inAmp)

{

    return 20. * log10(inAmp);

}

inline double DbToAmp(double inDb)

{

    return pow(10., 0.05 * inDb);

}

class PowerMeter

{

public:

    PowerMeter();

    void        Reset();

    void        SetSampleRate(double sr);

    void        Process_Int32(  const SInt32    *inSourceP,

                            int                 inSourceStride,

                            int                 inFramesToProcess);

    void        Process_Int16(  const SInt16    *inSourceP,

                            int                 inSourceStride,

                            int                 inFramesToProcess);

    void        ProcessSilence(int nframes);

    double      GetAveragePowerDB() const { return LinearToDB(GetAveragePowerLinear()); }

    double      GetPeakPowerDB() const { return LinearToDB(GetPeakPowerLinear()); }

    double      GetAveragePowerLinear() const { return mAveragePowerPeak; }

    double      GetPeakPowerLinear() const { return mMaxPeak; }

private:    

    void        ScaleDecayConstants(int inFramesToProcess);

    double      LinearToDB(double p) const { return (p <= kMinLinearPower) ? kMinDecibelsPower : AmpToDb(p); }

    void        SavePeaks(int inFramesToProcess, int averagePower, int maxSample);

private:

    double  mSampleRate;

    double  mPeakDecay1, mPeakDecay;

    double  mDecay1, mDecay;

    int     mPrevBlockSize;

    int     mAveragePower;

    int     mPeakHoldCount;

    double  mPeak;

    double  mAveragePowerPeak;

    double  mMaxPeak;

};

#endif // __PowerMeter