diff src/FeatureConditioner.h @ 103:593054bf6476 feature_conditioner

Pull out normalisation and specdiff stuff into FeatureConditioner

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/src/FeatureConditioner.h	Thu Dec 04 13:05:16 2014 +0000
@@ -0,0 +1,105 @@
+/* -*- c-basic-offset: 4 indent-tabs-mode: nil -*-  vi:set ts=8 sts=4 sw=4: */
+
+/*
+    Vamp feature extraction plugin using the MATCH audio alignment
+    algorithm.
+
+    Centre for Digital Music, Queen Mary, University of London.
+    
+    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 2 of the
+    License, or (at your option) any later version.  See the file
+    COPYING included with this distribution for more information.
+*/
+
+#ifndef FEATURE_CONDITIONER_H
+#define FEATURE_CONDITIONER_H
+
+#include <vector>
+
+/**
+ * Take a series of feature vectors and apply conditioning of some
+ * sort, such as normalisation or first-order derivative.
+ *
+ * Note that FeatureConditioner maintains internal frame-to-frame
+ * state: use one FeatureConditioner per audio source, and construct a
+ * new one for each new source.
+ */
+class FeatureConditioner
+{
+public:
+    enum Normalisation {
+
+        /** Do not normalise */
+        NoNormalisation,
+        
+        /** Normalise each feature vector to have a sum of 1 */
+        NormaliseToSum1,
+        
+        /** Normalise each feature vector by the long-term average of
+         *  the summed energy */
+        NormaliseToLTAverage,
+    };
+
+    enum OutputOrder {
+
+	/** Output the normalised features without further processing */
+	OutputFeatures,
+
+	/** Output the half-wave rectified difference between the
+	 * previous and current features instead of the straight
+	 * feature values. */
+	OutputRectifiedDerivative,
+    };
+
+    struct Parameters {
+
+	Parameters() :
+	    norm(NormaliseToSum1),
+	    order(OutputRectifiedDerivative),
+	    silenceThreshold(0.01),
+	    decay(0.99)
+	{}
+
+	/** Feature normalisation. */
+	Normalisation norm;
+
+	/** Type of output to generate (plain feature, derivative etc). */
+	OutputOrder order;
+
+	/** Silence threshold. If non-zero, any feature whose total
+	 *  energy (simply the sum of feature values) is below that
+	 *  threshold will be rounded down to all zeros. */
+	double silenceThreshold;
+
+        /** Frame-to-frame decay factor in calculating long-term average */
+	double decay;
+    };
+	
+    /**
+     * Construct a FeatureExtractor with the given parameters.
+     *
+     * Note that FeatureExtractor maintains internal frame-to-frame
+     * state: use one FeatureExtractor per audio source, and construct
+     * a new one for each new source.
+     */
+    FeatureConditioner(Parameters parameters) : m_params(parameters) { }
+
+    /**
+     * Process the given feature and return the conditioned feature.
+     */
+    std::vector<double> process(const std::vector<double> &feature);
+
+protected:
+    Parameters m_params;
+    
+    /** Long term average feature energy. */
+    double m_ltAverage;
+
+    /** The most recent feature, used for calculating the feature to
+     *  feature difference. This is therefore not yet normalised. */
+    std::vector<double> m_prev;
+};
+
+#endif