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;
036import org.openimaj.audio.SampleChunk;
037import org.openimaj.audio.processor.FixedSizeSampleAudioProcessor;
038import org.openimaj.audio.samples.SampleBuffer;
039
040/**
041 *      FIR filter is a multiplication of the frequency domain of a signal with the frequency
042 *      domain of a filter. That corresponds to a convolution in the time domain; that is,
043 *      a weighted sum of the previous input.
044 *
045 *      @author David Dupplaw (dpd@ecs.soton.ac.uk)
046 *  @created 22 May 2013
047 */
048public abstract class FIRFilter extends FixedSizeSampleAudioProcessor
049{
050        /** The coefficients for this filter */
051        private final double[] coefficients;
052
053        /**
054         *      @param stream
055         */
056        public FIRFilter( final AudioStream stream )
057        {
058                super( stream, 4, 3 );
059
060                this.coefficients = this.getCoefficients();
061                super.setWindowSize( this.coefficients.length );
062                super.setWindowStep( this.coefficients.length-1 );
063        }
064
065        /**
066         *      Returns the coefficients for the particular filter
067         *      @return coefficients
068         */
069        public abstract double[] getCoefficients();
070
071        /**
072         *      {@inheritDoc}
073         *      @see org.openimaj.audio.processor.FixedSizeSampleAudioProcessor#process(org.openimaj.audio.SampleChunk)
074         */
075        @Override
076        public SampleChunk process( final SampleChunk sample ) throws Exception
077        {
078                final SampleBuffer sb = sample.getSampleBuffer();
079
080                for( int c = 0; c < sample.getFormat().getNumChannels(); c++ )
081                {
082                        float acc = 0;
083                        for( int i = 0; i < this.coefficients.length; i++ )
084                                acc += sb.get(i) * this.coefficients[i];
085                        sb.set( 0, acc );
086                }
087
088                return sample;
089        }
090}