com.bleedobsidian.datawave.utils.Sinewave.java Source code

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Here is the source code for com.bleedobsidian.datawave.utils.Sinewave.java

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/*
 *    DataWave Library - A library that allows data to be sent between nodes via sound.
 *    Copyright (C) 2015  Jesse Prescott (BleedObsidian)
 *
 *    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 3 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, see <http://www.gnu.org/licenses/>.
 */

package com.bleedobsidian.datawave.utils;

import org.apache.commons.math3.complex.Complex;
import org.apache.commons.math3.transform.DftNormalization;
import org.apache.commons.math3.transform.FastFourierTransformer;
import org.apache.commons.math3.transform.TransformType;

import com.bleedobsidian.datawave.Audio;

/**
 * A utility class for manipulating sine waves.
 * 
 * @author Jesse Prescott (BleedObsidian)
 */
public class Sinewave {

    /**
     * Produce sound data from a sine wave.
     * 
     * @param sampleRate Sample rate.
     * @param frequency Frequency in Hertz.
     * @param duration Duration in seconds.
     * @param amplitude Volume scale.
     * 
     * @return Samples.
     */
    public static double[] generateSound(double sampleRate, double frequency, double duration, double amplitude) {
        int n = (int) (sampleRate * duration);
        double[] a = new double[n + 1];

        for (int i = 0; i <= n; i++) {
            a[i] = amplitude * Math.sin(2 * Math.PI * i * frequency / sampleRate);
        }

        return a;
    }

    /**
     * Calculate the frequency of sine wave from sound data.
     * 
     * @param sampleRate Sample rate.
     * @param samples Samples.
     * 
     * @return Frequency.
     */
    public static double calculateFrequency(double sampleRate, double[] samples) {
        FastFourierTransformer transformer = new FastFourierTransformer(DftNormalization.STANDARD);
        Complex[] complex = transformer.transform(samples, TransformType.FORWARD);

        double real;
        double im;
        double mag[] = new double[complex.length];

        for (int i = 0; i < complex.length; i++) {
            real = complex[i].getReal();
            im = complex[i].getImaginary();
            mag[i] = Math.sqrt((real * real) + (im * im));
        }

        double peak = 0.2;
        int index = -1;
        for (int i = 0; i < complex.length; i++) {
            if (peak < mag[i]) {
                index = i;
                peak = mag[i];
            }
        }

        return ((sampleRate * index) / Audio.SAMPLE_BUFFER_SIZE) * 2;
    }

}