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stcorrdsp.cc

/*
    Copyright (C) 2008 Fons Adriaensen <fons@kokkinizita.net>
    
    This program is free software; you can redistribute it and/or modify
    it under the terms of the GNU General Public License as published by
    the Free Software Foundation; either version 2 of the License, or
    (at your option) any later version.

    This program is distributed in the hope that it will be useful,
    but WITHOUT ANY WARRANTY; without even the implied warranty of
    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
    GNU General Public License for more details.

    You should have received a copy of the GNU General Public License
    along with this program; if not, write to the Free Software
    Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
*/


#include <math.h>
#include "stcorrdsp.h"


float  Stcorrdsp::_w1;
float  Stcorrdsp::_w2; 



Stcorrdsp::Stcorrdsp (void) :
    _zl (0),
    _zr (0),
    _zlr (0),
    _zll (0),
    _zrr (0)
{
}


Stcorrdsp::~Stcorrdsp (void)
{
}


void Stcorrdsp::process (float *pl, float *pr, int n)
{
    // Called by JACK's process callback.
    //
    // pl : pointer to left channel sample buffer
    // pr : pointer to right channel sample buffer
    // n  : number of samples to process

    float zl, zr, zlr, zll, zrr;

    zl = _zl;
    zr = _zr;
    zlr = _zlr;
    zll = _zll;
    zrr = _zrr;
    while (n--)
    {
      zl += _w1 * (*pl++ - zl) + 1e-20f;
      zr += _w1 * (*pr++ - zr) + 1e-20f;
      zlr += _w2 * (zl * zr - zlr);
      zll += _w2 * (zl * zl - zll);
      zrr += _w2 * (zr * zr - zrr);
    }
    _zl = zl;
    _zr = zr;
    _zlr = zlr;
    _zll = zll;
    _zrr = zrr;
}


float Stcorrdsp::read (void)
{
    // Called by display process approx. 30 times per second.

    return _zlr / sqrtf (_zll * _zrr + 1e-12f);
}


void Stcorrdsp::init (int fsamp, float flp, float tcf)
{
    // Called by initialisation code.
    //
    // fsamp = sample frequency
    // flp   = lowpass frequency
    // tcf   = correlation filter time constant

    _w1 = 6.28f * flp / fsamp;
    _w2 = 1 / (tcf * fsamp);
}

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