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AvgChromaScalar.java

        /*
 *  Copyright 2006-2007 Columbia University.
 *
 *  This file is part of MEAPsoft.
 *
 *  MEAPsoft is free software; you can redistribute it and/or modify
 *  it under the terms of the GNU General Public License version 2 as
 *  published by the Free Software Foundation.
 *
 *  MEAPsoft 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 MEAPsoft; if not, write to the Free Software
 *  Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA
 *  02110-1301 USA
 *
 *  See the file "COPYING" for the text of the license.
 */

package com.meapsoft.featextractors;

import com.meapsoft.MEAPUtil;
import com.meapsoft.STFT;

public class AvgChromaScalar extends AvgChroma {

  // Default constructor 
  public AvgChromaScalar() {
      super();
  }

  public AvgChromaScalar(int N, int outDim, double sampleRate) {
      super(N, outDim, sampleRate);
  }


  public double[] features(STFT stft, long startFrame, int length) {
    double[] chromaVal = new double[1];
    
    double [] chromSpec;

    chromSpec = super.features(stft, startFrame, length);

    // calculate complex average chroma
    double re = 0, im = 0;
    for (int bin = 0; bin < outDim; ++bin) {
        re = re + chromSpec[bin] * Math.cos(6.28318531*bin/outDim);
        im = im + chromSpec[bin] * Math.sin(6.28318531*bin/outDim);
    }

    double meanchrom = outDim * (Math.atan2(im, re) / 6.28318531);   
    // atan2 returns -pi..pi
    // fold back to +ve octave
    if (meanchrom < 0) 
        meanchrom += outDim;

    chromaVal[0] = meanchrom;

    return chromaVal;
  }
  
  public String description()
  {
          return "Single value giving dominant semitone within the octave.";
  }
}

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