Package org.vocvark.AudioFeatures

Source Code of org.vocvark.AudioFeatures.BeatHistogram

/*
* @(#)BeatHistogram.java  1.0  April 5, 2005.
*
* McGill Univarsity
*/

package org.vocvark.AudioFeatures;

import org.vocvark.DataTypes.FeatureDefinition;

/**
* A feature extractor that extracts the Beat Histogram from a signal. This is
* histogram showing the strength of different rhythmic periodicities in a
* signal.
* <p/>
* This is calculated by taking the RMS of 256 windows and then taking
* the FFT of the result.
* <p/>
* No extracted feature values are stored in objects of this class.
* <p/>
* <b>IMPORTANT:
* </P>
* The window size of 256 RMS windows used here is hard-coded into the class
* BeatHistogramLabels. Any changes to the window size in this class must be
* made there as well.</b>
* <p/>
* Daniel McEnnis 05-07-05 Added setElement, getElement, setElement, and clone
* functions
*
* @author Cory McKay
*/
public class BeatHistogram extends FeatureExtractorBaseImpl {

    private int number_windows = 256;

    /* CONSTRUCTOR ************************************************************* */

    /**
     * Basic constructor that sets the definition and dependencies (and their
     * offsets) of this feature.
     */
    public BeatHistogram() {
        String name = "Beat Histogram";
        String description = "A histogram showing the relative strength of different "
                + "rhythmic periodicities (tempi) in a signal. Found by "
                + "calculating the auto-correlation of the RMS.";
        boolean is_sequential = true;
        int dimensions = 0;
        definition = new FeatureDefinition(name, description, is_sequential,
                dimensions);

        // int number_windows = 256;

        dependencies = new String[number_windows];
        for (int i = 0; i < dependencies.length; i++)
            dependencies[i] = "Root Mean Square";

        offsets = new int[number_windows];
        for (int i = 0; i < offsets.length; i++)
            offsets[i] = 0 - i;
    }

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

    /**
     * Extracts this feature from the given samples at the given sampling rate
     * and given the other feature values.
     * <p/>
     * In the case of this feature the sampling_rate 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 index
     *                             indicates the feature/window and the second indicates the
     *                             value.
     * @return The extracted feature value(s).
     * @throws Exception Throws an informative exception if the feature cannot be
     *                   calculated.
     */
    public double[] extractFeature(double[] samples, double sampling_rate,
                                   double[][] other_feature_values) throws Exception {
        double[] rms = new double[other_feature_values.length];
        for (int i = 0; i < rms.length; i++)
            rms[i] = other_feature_values[i][0];

        double effective_sampling_rate = sampling_rate / ((double) rms.length);

        int min_lag = (int) (0.286 * effective_sampling_rate);
        int max_lag = (int) (3.0 * effective_sampling_rate);
        double[] auto_correlation = org.vocvark.jAudioTools.DSPMethods
                .getAutoCorrelation(rms, min_lag, max_lag);
        return auto_correlation;
    }

    /**
     * Helper function to set window length for this feature. Note that this
     * feature does *not* conform to the syntax of setWindow so this feature is
     * not affected by a global window change. This is necessary since the beat
     * bins have a different meaning than most windowed features.
     *
     * @param n new number of beat bins
     * @throws Exception thrown if the new value is less than 2
     */
    public void setWindowLength(int n) throws Exception {
        if (n < 2) {
            throw new Exception(
                    "BeatHistogram window length must be greater than 1");
        } else {
            number_windows = n;
            dependencies = new String[number_windows];
            offsets = new int[number_windows];
            for (int i = 0; i < number_windows; ++i) {
                dependencies[i] = "Root Mean Square";
                offsets[i] = 0 - i;
            }
        }
    }

    /**
     * Function permitting an unintelligent outside function (ie. EditFeatures
     * frame) to get the default values used to populate the table's entries.
     * The correct index values are inferred from definition.attribute value.
     *
     * @param index which of Beat Histograms's attributes should be edited.
     */
    public String getElement(int index) throws Exception {
        if (index != 0) {
            throw new Exception("INTERNAL ERROR: invalid index " + index
                    + " sent to AreaMoments:getElement");
        } else {
            return Integer.toString(number_windows);
        }
    }

    /**
     * Function permitting an unintelligent outside function (i.e. EditFeatures
     * frame) to set the default values used to populate the table's entries.
     * Like getElement, the correct index values are inferred from the
     * definition.attributes value.
     *
     * @param index attribute to be set
     * @param value new value of the attribute
     */
    public void setElement(int index, String value) throws Exception {
        if (index != 0) {
            throw new Exception("INTERNAL ERROR: invalid index " + index + " sent to AreaMoments:setElement");
        } else {
            try {
                int type = Integer.parseInt(value);
                setWindowLength(type);
            } catch (Exception e) {
                throw new Exception("Length of Area Method of Moments must be an integer");
            }
        }
    }

    /**
     * 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() {
        BeatHistogram ret = new BeatHistogram();
        ret.number_windows = number_windows;
        return ret;
    }

}
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