/home/marsyas/marsyas/src/marsyas/SCF.cpp

/*
** Copyright (C) 1998-2006 George Tzanetakis <gtzan@cs.uvic.ca>
**  
** 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., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
*/

#include "SCF.h"

using namespace std;
using namespace Marsyas;

SCF::SCF(mrs_string name):MarSystem("SCF",name)
{
}

SCF::~SCF()
{
}

MarSystem* 
SCF::clone() const 
{
    return new SCF(*this);
}

void
SCF::myUpdate(MarControlPtr sender)
{
    (void) sender;
    MRSDIAG("SCF.cpp - SCF:myUpdate");

    //MPEG-7 audio standard:
    //assumes an 1/4 octave frequency resolution,
    //resulting in 24 frequency bands between 250Hz and 16kHz.
    //If the signal under analysis does not contain frequencies
    //above a determined value (e.g. due to signal sampling rate or
    //bandwidth limitations), the nr of bands should be reduced. 

    mrs_natural i;

    //nrBands_ = getctrl("mrs_natural/nrbands");// can this be received as a control value?
    nrBands_ = 24;
    //can this parameter be dynamically modified, depending on the
    //sampling frequency?!?
    nrValidBands_ = nrBands_; 

    setctrl(ctrl_onSamples_, 1);
    setctrl(ctrl_onObservations_, nrBands_); 
    setctrl(ctrl_osrate_, ctrl_israte_);

    //features names
    ostringstream oss;
    for (i = 0; i < nrBands_; ++i)
        oss << "SCF_" << i+1 << ",";
    setctrl(ctrl_onObsNames_, oss.str());

    edge_.create(nrBands_ + 1);
    bandLoEdge_.create(nrBands_);
    bandHiEdge_.create(nrBands_);

    //nominal band edges (Hz) -> reference = 1kHz (MPEG7)
    for(i = 0 ; i < nrBands_ + 1 ; ++i)
    {
        // 1/4 octave resolution (MPEG7)
        edge_(i)= 1000.0f * pow(2.0f, (0.25f * (i - 8))); 
    }
    // overlapped low and high band edges (Hz)
    for (i = 0; i < nrBands_; ++i)
    {
        bandLoEdge_(i) = edge_(i) * 0.95f; //band overlapping (MPEG7) 
        bandHiEdge_(i) = edge_(i+1) * 1.05f; //band overlapping (MPEG7)
    }

    spectrumSize_ = ctrl_inObservations_->to<mrs_natural>();//PowerSpectrum returns N/2+1 spectral points
    //spectrumBinFreqs_.create(spectrumSize_);

    // spectrum sampling rate - not audio 
    df_ = ctrl_israte_->to<mrs_real>();

    //calculate the frequency (Hz) of each FFT bin
    //for (mrs_natural k=0; k < spectrumSize_ ; k++)
    //  spectrumBinFreqs_(k) = (float) k * df_;

    //calculate FFT bin indexes for each band's edges
    il_.resize(nrBands_);
    ih_.resize(nrBands_);
    for(i = 0; i < nrBands_; ++i)
    {
        //round to nearest int (MPEG7)
        il_[i] = (mrs_natural)(bandLoEdge_(i)/df_ + 0.5f); 
        ih_[i] = (mrs_natural)(bandHiEdge_(i)/df_ + 0.5f); 

        //must verify if sampling rate is enough
        //for the specified nr of bands. If not, 
        //reduce nr of valid freq. bands
        if(ih_[i] >= spectrumSize_) //if ih_[i] >= N/2+1 = spectrumSize_ = inObservations ...
        {
            nrValidBands_ = i;
            il_.resize(nrValidBands_);
            ih_.resize(nrValidBands_);
            break;
        }
    }
}

void 
SCF::myProcess(realvec& in, realvec& out)
{
    mrs_natural i, k, bandwidth;
    double c, maxc;
    double aritMean ;

    //default SCF value = 1.0; (defines SCF=1.0 for silence)
    out.setval(1.0);

    //MPEG7 defines a grouping mechanism for the frequency bands above 1KHz
    //in order to reduce computational effort of the following calculation.
    //For now such grouping mechanism is not implemented...
    for(i = 0; i < nrValidBands_; ++i)
    {
        aritMean = 0.0;
        maxc = 0.0;
        bandwidth = ih_[i] - il_[i] + 1;
        for(k = il_[i]; k <= ih_[i]; k++)
        {
            c = in(k); //power spectrum coeff
            aritMean += c / bandwidth;
            if(c > maxc)
                maxc = c;
        }
        if (aritMean != 0.0)
        {
            out(i) = (float)(maxc/aritMean);
        }
        //else //mean power = 0 => silence...
        //  out(i) = 1.0; //as used for the SFM (MPEG-7)...
    }

    //for freq bands above the nyquist freq
    //return SFM value defined in MPEG7 for silence
    //for(i = nrValidBands_; i < nrBands_; ++i)
    //  out(i) = 1.0;
}

---