Android example source code file (BeatTimingsAdjuster.java)

This example Android source code file (BeatTimingsAdjuster.java) is included in the DevDaily.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Android by Example" ^TM.

Java - Android tags/keywords

arraylist, beattimingsadjuster, target, util

The BeatTimingsAdjuster.java Android example source code

/*
 * Copyright (C) 2008 Google Inc.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package com.google.clickin2dabeat;

import java.util.ArrayList;

/**
 * Adjusts the times for the beat targets using a linear least-squares fit.
 */
public class BeatTimingsAdjuster {
  private double[] adjustedBeatTimes;

  public void setRawBeatTimes(ArrayList<Integer> rawBeatTimes) {
    double[] beatTimes = new double[rawBeatTimes.size()];
    for (int i = 0; i < beatTimes.length; i++) {
      beatTimes[i] = rawBeatTimes.get(i);
    }

    adjustedBeatTimes = new double[beatTimes.length];
    double[] beatNumbers = {0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10};
    double n = beatNumbers.length;
    // Some things can be computed once and never computed again
    double[] beatNumbersXNumbers = multiplyArrays(beatNumbers, beatNumbers);
    double sumOfBeatNumbersXNumbers = sum(beatNumbersXNumbers);
    double sumOfBeatNumbers = sum(beatNumbers);
    // The divisor is:
    // (n * sum(beatNumbersXNumbers) - (sum(beatNumbers) * sum(beatNumbers)))
    // Since these are all constants, they can be computed first for better
    // efficiency.
    double divisor = (n * sum(beatNumbersXNumbers) - (sum(beatNumbers) * sum(beatNumbers)));


    // Not enough data to adjust for the first 5 beats
    for (int i = 0; (i < beatTimes.length) && (i < 5); i++) {
      adjustedBeatTimes[i] = beatTimes[i];
    }

    // Adjust time for beat i by using timings for beats i-5 through i+5
    double[] beatWindow = new double[beatNumbers.length];
    for (int i = 0; i < beatTimes.length - 10; i++) {
      System.arraycopy(beatTimes, i, beatWindow, 0, beatNumbers.length);
      double[] beatNumbersXTimes = multiplyArrays(beatNumbers, beatWindow);
      double a =
          (sum(beatTimes) * sumOfBeatNumbersXNumbers - sumOfBeatNumbers * sum(beatNumbersXTimes))
              / divisor;

      double b = (n * sum(beatNumbersXTimes) - sumOfBeatNumbers * sum(beatTimes)) / divisor;

      adjustedBeatTimes[i + 5] = a + b * beatNumbers[5];
    }

    if (beatTimes.length - 10 < 0) {
      return;
    }

    // Not enough data to adjust for the last 5 beats
    for (int i = beatTimes.length - 10; i < beatTimes.length; i++) {
      adjustedBeatTimes[i] = beatTimes[i];
    }
  }

  public ArrayList<Target> adjustBeatTargets(ArrayList rawTargets) {
    ArrayList<Target> adjustedTargets = new ArrayList();
    int j = 0;
    double threshold = 200;
    for (int i = 0; i < rawTargets.size(); i++) {
      Target t = rawTargets.get(i);
      while ((j < adjustedBeatTimes.length) && (adjustedBeatTimes[j] < t.time)) {
        j++;
      }
      double prevTime = 0;
      if (j > 0) {
        prevTime = adjustedBeatTimes[j - 1];
      }
      double postTime = -1;
      if (j < adjustedBeatTimes.length) {
        postTime = adjustedBeatTimes[j];
      }
      if ((Math.abs(t.time - prevTime) < Math.abs(t.time - postTime))
          && Math.abs(t.time - prevTime) < threshold) {
        t.time = prevTime;
      } else if ((Math.abs(t.time - prevTime) > Math.abs(t.time - postTime))
          && Math.abs(t.time - postTime) < threshold) {
        t.time = postTime;
      }
      adjustedTargets.add(t);
    }
    return adjustedTargets;
  }


  private double sum(double[] numbers) {
    double sum = 0;
    for (int i = 0; i < numbers.length; i++) {
      sum = sum + numbers[i];
    }
    return sum;
  }


  private double[] multiplyArrays(double[] numberSetA, double[] numberSetB) {
    double[] sqArray = new double[numberSetA.length];
    for (int i = 0; i < numberSetA.length; i++) {
      sqArray[i] = numberSetA[i] * numberSetB[i];
    }
    return sqArray;
  }

}