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OnsetDetector.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;

import java.util.ArrayList;

/*
 * Base class for all onset detectors.  Looks at an STFT and
 * determines if there is anything that looks like an onset in it.
 *
 * @author Mike Mandel ([email protected])
 */

public class OnsetDetector implements FrameListener {
  STFT stft;
  long lastSeen;
  int histLen = 4, onsLen = 512;
  double[][] history;
  double[] onsets;

  ArrayList listeners;

  // Keep track of the mean of each band with a leaky integrator
  double[] state;

  // Controls the length over which the mean is calculated for each
  // band.
  double adaptation = 0.01;

  // The threshold for an onset, as a fraction of the mean for each
  // band
  double bandThresh = 2;

  // The fraction of band onsets required to trigger a global onset
  double bandFrac = 0.3;

  public OnsetDetector(STFT stft, double bandThresh, double bandFrac) {
    this.stft = stft;
    this.bandThresh = bandThresh;
    this.bandFrac = bandFrac;

    this.listeners = new ArrayList();
    this.history = new double[histLen+1][];
    this.onsets = new double[onsLen];

    state = new double[stft.getRows()];
    for(int i=0; i<state.length; i++)
      state[i] = 0.5/adaptation;

    stft.addFrameListener(this);
  }

  public void addOnsetListener(OnsetListener listener) {
    listeners.add(listener);
  }
  public void removeOnsetListener(OnsetListener listener) {
    listeners.remove(listener);
  }
  protected void notifyListeners(long frAddr, int zeroFrames) {
    for(int i=0; i<listeners.size(); i++)
      ((OnsetListener)listeners.get(i)).newOnset(frAddr, zeroFrames);
  }


  // Determine if there has been an onset since the last time this was
  // called.  If there was, notify our listeners.
  public void newFrame(STFT stft, long newestFrame) {
    // Get the history for the first column to be analyzed
    for(int i=0; i<histLen+1; i++) {
      history[i] = stft.getFrame(lastSeen+1-histLen+i);
      if(history[i] == null)
        history[i] = new double[stft.getRows()];
    }

    // Analyze each column in turn, bucket-brigade the history
    for(long fr = lastSeen+1; fr <= newestFrame; fr++) {
      double result;
      int curOns = (int)(fr % onsets.length);
      onsets[curOns] = 0;

      for(int band=0; band<history[0].length; band++) {
        result = 0;
        for(int i=0; i<histLen; i++)
          result += Math.abs(history[i][band] - history[histLen][band]);

        // See if this band is an onset
        if(result > bandThresh*state[band])
          ++onsets[curOns];
        
        // update running mean
        state[band] = adaptation*result + (1-adaptation)*state[band];
      }

      // get the next history
      for(int i=0; i<histLen; i++)
        history[i] = history[i+1];
      history[histLen] = stft.getFrame(fr);
    }

    checkOnsets(lastSeen, newestFrame);

    // No onsets found
    lastSeen = newestFrame;
  }

  public void checkOnsets(long lastSeen, long newestFrame) {
    // Simple onset detector: if enough bands have onsetted, trigger
    // a global onset
    for(long fr = lastSeen+1; fr <= newestFrame; fr++) {
      int curOns = (int)(fr % onsets.length);

      if(onsets[curOns] > bandFrac*state.length) {
//      System.out.print((int)(onsets[curOns]/10));
//      System.out.print("*");
        notifyListeners(fr, 0);
      }
    }
  }
}

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