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.AudioStream;
036
037/**
038 *      Applies a Hanning window on top of the audio signal.
039 *  
040 *      @see "http://cnx.org/content/m0505/latest/"
041 *  @author David Dupplaw (dpd@ecs.soton.ac.uk)
042 *      @created 31 Oct 2011
043 */
044public class HanningAudioProcessor extends WeightedWindowedAudioProcessor
045{
046        /**
047         *      Default constructor for non chainable processing.
048         *      @param sizeRequired Size of the window required 
049         */
050        public HanningAudioProcessor( final int sizeRequired )
051        {
052                super( sizeRequired );
053        }
054        
055        /**
056         *      Chainable constructor. Takes the audio stream and the size required.
057         * 
058         *  @param stream The audio stream to process
059         *  @param sizeRequired The size of window required.
060         */
061        public HanningAudioProcessor( final AudioStream stream, final int sizeRequired )
062    {
063            super( stream, sizeRequired );
064    }
065
066        /**
067         *      Constructor that takes the size of the window and the number of samples
068         *      overlap.
069         * 
070         *      @param nSamplesInWindow Samples in window
071         *      @param nSamplesOverlap Samples in window overlap
072         */
073        public HanningAudioProcessor( final int nSamplesInWindow, final int nSamplesOverlap )
074        {
075                super( nSamplesInWindow, nSamplesOverlap );
076        }
077
078        /**
079         *      Chainable constructor that takes the size of the window and 
080         *      the number of samples overlap.
081         * 
082         *      @param as The chained audio stream
083         *      @param nSamplesInWindow Samples in window
084         *      @param nSamplesOverlap Samples in window overlap
085         */
086        public HanningAudioProcessor( final AudioStream as, final int nSamplesInWindow,
087                        final int nSamplesOverlap )
088        {
089                super( as, nSamplesInWindow, nSamplesOverlap );
090        }
091
092        /**
093         *      Generate the cos table cache
094         *      @param length The length of the window to generate (per channel)
095         *      @param nc The number of channels for which to generate a weight table
096         */
097        @Override
098        protected void generateWeightTableCache( final int length, final int nc )
099        {
100                final int ns = length;
101                this.weightTable = new double[ length ];
102                for( int n = 0; n < ns; n++ )
103                        for( int c = 0; c < nc; c++ )
104                                this.weightTable[n*nc+c] = 0.5*(1-Math.cos((2*Math.PI*n)/ns));
105        }       
106}