/*

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

See LICENSE.txt for this sample’s licensing information

*/

class PinkFilter

{

public:

    PinkFilter() {Reset();};

    void            Reset() {buf0=buf1=buf2=buf3=buf4=buf5=buf6=0.0;};

    void            Process(    const float *inSourceP,

                                float   *inDestP,

                                int     inFramesToProcess,

                                int     inInputHop,

                                int     inOutputHop

                                )

    {

        register int n = inFramesToProcess;

        register const float *sourceP = inSourceP;

        register float *destP = inDestP;

        register int inputHop = inInputHop;

        register int outputHop = inOutputHop;

        while(n--)

        {

            float white= *sourceP;

            sourceP += inputHop;

            // pink noise algorithim courtesy of 

            // http://www.firstpr.com.au/dsp/pink-noise/

            buf0= 0.99886 * buf0 + 0.0555179 * white;

            buf1= 0.99332 * buf1 + 0.0750759 * white;

            buf2= 0.96900 * buf2 + 0.1538520 * white;

            buf3= 0.86650 * buf3 + 0.3104856 * white;

            buf4= 0.55000 * buf4 + 0.5329522 * white;

            buf5= -0.7616 * buf5 + 0.0168980 * white;

            float pink=buf0 + buf1 + buf2 + buf3 + buf4  

                + buf5 + buf6 + white * .5362;

            buf6= 0.115926 * white;

            *destP = pink;

            destP += outputHop;

        }

    };

private:

    float           buf0;

    float           buf1;

    float           buf2;

    float           buf3;

    float           buf4;

    float           buf5;

    float           buf6;

};

/*

Pink filter:

    white=(whichever method you choose);

    buf0=0.997 * buf0 + 0.029591 * white;

    buf1=0.985 * buf1 + 0.032534 * white;

    buf2=0.950 * buf2 + 0.048056 * white;

    buf3=0.850 * buf3 + 0.090579 * white;

    buf4=0.620 * buf4 + 0.108990 * white;

    buf5=0.250 * buf5 + 0.255784 * white;

    pink=buf0 + buf1 + buf2 + buf3 + buf4  

        + buf5;

*/

#include "TRandom.h"

#include "Biquad.h"

class PinkNoiseGenerator

{

public:

    PinkNoiseGenerator(Float32 inSampleRate )

    {

        nyquist = 0.5 * inSampleRate;

        rumbleFilter.GetHipassParams(10.0/*Hertz*/ / nyquist, 0.0 );

    }

    void Render(Float32 *inBuffer, UInt32 inNumFrames, Float32 inVolume )

    {

        const Float32 kInv32768 = (1.0 / 32768.0) * 0.5;

        Float32 *destP = inBuffer;

        int n = inNumFrames;

        while(n--)

        {

            SInt32 r = SInt32(GetRandomLong(65536) ) - 32768;

            Float32 sample = r * kInv32768 * inVolume;

            *destP++ = sample;

        }

        // filter "backwards" since kernel is in reverse order

        filter.Process( inBuffer,

                        inBuffer,

                        inNumFrames,

                        1,

                        1

                        );

        // Hipass rumble filter to remove potential skanky DC offset

        rumbleFilter.Process(   inBuffer,

                                inBuffer,

                                inNumFrames,

                                1,

                                1

                                );

    }

private:

    float           nyquist;

    Biquad          rumbleFilter;

    PinkFilter      filter;

};