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AvgFreqSimple.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 java.util.Arrays;

import com.meapsoft.MEAPUtil;
import com.meapsoft.FeatExtractor;
import com.meapsoft.RingMatrix;
import com.meapsoft.STFT;

public class AvgFreqSimple extends FeatureExtractor {
  // earliest FFT bin to use
  static final int FIRSTBAND = 3;

  //double[] pitchWt;
  protected double[] linSpec;

  protected double bin2hz;
  protected int N;

  // Default constructor 
  public AvgFreqSimple() {
      this(FeatExtractor.nfft/2+1, FeatExtractor.feSamplingRate);
  }

  public AvgFreqSimple(int N, double sampleRate) {
      this.N = N;
      linSpec = new double[N];

      // Create the weighting profile for choosing the pitch
      // Gaussian in log-F space centered on 110Hz with SD of 2 octaves

      bin2hz = sampleRate / (2*(N-1));
  }

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

    boolean recalculateSTFT = stft.getRows() != N;
    RingMatrix newstft = null;
    if(recalculateSTFT) {
        // keep the same number of frames as in stft
        newstft = STFT.getSTFT(stft.getSamples(startFrame, startFrame+length), (N-1)*2, stft.nhop);
        length = newstft.getColumns();
    }    
    
        //if there are no features we just bail.
        if (length == 0)  
                return null;

    double wtdsum = 0;
    double sumwts = 0;

    // collect average linear spectrum
    Arrays.fill(linSpec, 0);
    for(int frame=0; frame<length; frame++) {

        if(!recalculateSTFT)
            curFrame = stft.getFrame(startFrame+frame);
        else
            curFrame = newstft.getColumn(frame);

        if(curFrame != null) {
            for(int band=0; band<linSpec.length; band++)
                linSpec[band] += Math.pow(10,curFrame[band]/10) / length;
        }
    }

    // now pick best peak from linspec

    double pmax = -1;
    int maxbin = 0;
    for(int band=FIRSTBAND; band<N; band++) {
        //double pwr = pitchWt[band]*linSpec[band];
        double pwr = linSpec[band];
                if (pwr > pmax) {
                    pmax = pwr;
                    maxbin = band;
                }
    }

    // cubic interpolation
    double yz = linSpec[maxbin];
    double ym = linSpec[maxbin-1];
    double yp = linSpec[maxbin+1];
    //treating Y as k(x-x0)^2 + c, we have samples at y(0), y(-1), y(1)
    // yz = k x0^2 + c
    // yp = k (1-x0)^2 + c  = k + k x0 ^ 2 - 2 k x0 + c
    // ym = k (1+x0)^2 + c  = k + k x0 ^ 2 + 2 k x0 + c
    double k  = (yp+ym)/2-yz;
    double x0 = (ym-yp)/(4*k);
    double c  = yz - k*Math.pow(x0,2);
    // y = kx^2 +kx0^2 -2kx0.x +c
    // dy/dx = 2kx - 2kx0 = 0 when x = x0

        //System.out.println("bin2hz: " + bin2hz + " maxbin: " + maxbin + " x0: " + x0);
    //pitch[0] = hz2octs(bin2hz * (maxbin + x0));
        freq[0] = bin2hz * (maxbin + x0);
    return freq;
  }

  public String description()
  {
          return "Provides a frequency estimation for each segment of sound.";
  }
}

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