/*
* @(#)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;
}
}