Package org.vocvark.AudioFeatures

Source Code of org.vocvark.AudioFeatures.StrongestFrequencyViaSpectralCentroid

/*
* @(#)StrongestFrequencyViaSpectralCentroid.java  1.0  April 7, 2005.
*
* McGill Univarsity
*/

package org.vocvark.AudioFeatures;

import org.vocvark.DataTypes.FeatureDefinition;


/**
* A feature extractor that finds the strongest frequency in Hz in a signal
* by looking at the spectral centroid.
* <p/>
* <p>This is found by mapping the fraction in the spectral centroid to a
* frequency in Hze
* <p/>
* <p>No extracted feature values are stored in objects of this class.
*
* @author Cory McKay
*/
public class StrongestFrequencyViaSpectralCentroid
        extends FeatureExtractorBaseImpl {
    /* CONSTRUCTOR **************************************************************/


    /**
     * Basic constructor that sets the definition and dependencies (and their
     * offsets) of this feature.
     */
    public StrongestFrequencyViaSpectralCentroid() {
        String name = "Strongest Frequency Via Spectral Centroid";
        String description = "The strongest frequency component of a signal, in Hz, " +
                "found via the spectral centroid.";
        boolean is_sequential = true;
        int dimensions = 1;
        definition = new FeatureDefinition(name,
                description,
                is_sequential,
                dimensions);

        dependencies = new String[2];
        dependencies[0] = "Spectral Centroid";
        dependencies[1] = "Power Spectrum";

        offsets = new int[2];
        offsets[0] = 0;
        offsets[1] = 0;
    }


    /* PUBLIC METHODS **********************************************************/


    /**
     * Extracts this feature from the given samples at the given sampling
     * rate and given the other feature values.
     * <p/>
     * <p>In the case of this feature, the sampling_rate parameter is ignored.
     *
     * @param samples              The samples to extract the feature from.
     * @param sampling_rate        The sampling rate that the samples are
     *                             encoded with.
     * @param other_feature_values The values of other features that are
     *                             needed to calculate this value. The
     *                             order and offsets of these features
     *                             must be the same as those returned by
     *                             this class's getDependencies and
     *                             getDependencyOffsets methods respectively.
     *                             The first indice indicates the feature/window
     *                             and the second indicates the value.
     * @throws Exception Throws an informative exception if
     *                   the feature cannot be calculated.
     * @return The extracted feature value(s).
     */
    public double[] extractFeature(double[] samples,
                                   double sampling_rate,
                                   double[][] other_feature_values)
            throws Exception {
        double spectral_centroid = other_feature_values[0][0];
        double[] pow_spectrum = other_feature_values[1];
        double[] result = new double[1];
        result[0] = (spectral_centroid / pow_spectrum.length) * (sampling_rate / 2.0);
        return result;
    }

    /**
     * Create an identical copy of this feature. This permits FeatureExtractor
     * to use the prototype pattern to create new composite features using
     * metafeatures.
     */
    public Object clone() {
        return new StrongestFrequencyViaSpectralCentroid();
    }
}
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