001/**
002 * Copyright (c) 2011, The University of Southampton and the individual contributors.
003 * All rights reserved.
004 *
005 * Redistribution and use in source and binary forms, with or without modification,
006 * are permitted provided that the following conditions are met:
007 *
008 *   *  Redistributions of source code must retain the above copyright notice,
009 *      this list of conditions and the following disclaimer.
010 *
011 *   *  Redistributions in binary form must reproduce the above copyright notice,
012 *      this list of conditions and the following disclaimer in the documentation
013 *      and/or other materials provided with the distribution.
014 *
015 *   *  Neither the name of the University of Southampton nor the names of its
016 *      contributors may be used to endorse or promote products derived from this
017 *      software without specific prior written permission.
018 *
019 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
020 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
021 * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
022 * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR
023 * ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
024 * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
025 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON
026 * ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
027 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
028 * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
029 */
030/**
031 * 
032 */
033package org.openimaj.audio.filters;
034
035import org.openimaj.audio.SampleChunk;
036import org.openimaj.audio.processor.AudioProcessor;
037
038/**
039 *      Uses a {@link MusicalNoteFilterBank} to determine the power output of
040 *      the notes of a western scale over the frame. It calculates the power
041 *      difference between successive frames to determine whether a new note
042 *      has been detected.
043 *
044 *      @author David Dupplaw <dpd@ecs.soton.ac.uk>
045 *  @created 22 May 2012
046 *      @version $Author$, $Revision$, $Date$
047 */
048public class MusicalNoteOnsetDetector extends AudioProcessor
049{
050        /** The filter bank to use */
051        private final MusicalNoteFilterBank filterBank = new MusicalNoteFilterBank( 60, 72, null );
052        
053        /** The previous calculated output power */
054        private double previousPower = 0;
055        
056        /** Whether an onset was detected during the last process */
057        private boolean onsetDetected = false;
058        
059        /** The threshold over which onset is detected */
060        private final double threshold = 100;
061        
062        /** 
063         *      {@inheritDoc}
064         *      @see org.openimaj.audio.processor.AudioProcessor#process(org.openimaj.audio.SampleChunk)
065         */
066        @Override
067        public SampleChunk process( final SampleChunk sample ) throws Exception
068        {
069                this.filterBank.process( sample );
070                final double p = this.filterBank.getOutputPower();
071                
072                final double delta = Math.abs( this.previousPower - p );
073                
074                if( delta > this.threshold )
075                        this.onsetDetected = true;
076                
077                this.previousPower = p;
078                
079                return sample;
080        }
081
082        /**
083         *      Returns whether an onset was detected during the last processing cycle.
084         *      @return TRUE if an onset was detected during the last processing cycle;
085         *              FALSE otherwise.
086         */
087        public boolean hasOnsetBeenDetected()
088        {
089                return this.onsetDetected;
090        }
091}