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.analysis;
034
035import org.openimaj.audio.SampleChunk;
036import org.openimaj.audio.filters.VolumeAdjustProcessor;
037import org.openimaj.audio.processor.AudioProcessor;
038import org.openimaj.audio.samples.SampleBuffer;
039
040/**
041 *      Calculates the scalar necessary to achieve peak value of the loudest part of
042 *      the given input signal. This scalar can be retrieved using the 
043 *      {@link #getVolumeScalar()} method which will return the scalar as it
044 *      has currently been calculated for the stream which has passed. This will
045 *      only return the correct value for the whole audio stream once the whole
046 *      audio stream has passed through the processor. This processor will not
047 *      perform attenuation - that is, the volume scalar will always be greater
048 *      than 1 (and positive).
049 *      <p>
050 *      The value of the peak volume scalar is compatible with the 
051 *      {@link VolumeAdjustProcessor} which can adjust the volume to the maximum
052 *      peak value.
053 *
054 *      @author David Dupplaw (dpd@ecs.soton.ac.uk)
055 *  @created 10 Dec 2012
056 *      @version $Author$, $Revision$, $Date$
057 */
058public class PeakNormalisationCalculator extends AudioProcessor
059{
060        /** The peak scalar as it's been calcultated so far in the stream */
061        private float scalar = Float.MAX_VALUE;
062        
063        /** 
064         *      {@inheritDoc}
065         *      @see org.openimaj.audio.processor.AudioProcessor#process(org.openimaj.audio.SampleChunk)
066         */
067        @Override
068        public SampleChunk process( final SampleChunk sample ) throws Exception
069        {
070                // This allows us to retrieve samples that are scaled to 0..1 float values
071                final SampleBuffer sb = sample.getSampleBuffer();
072                
073                for( final float s : sb )
074                        if( Math.abs(s) * this.scalar > 1 )
075                                this.scalar = 1/Math.abs(s);
076                
077                return sample;
078        }
079
080        /**
081         *      Returns the calculated peak scalar as it currently stands in the stream.
082         *      If no audio has passed through the processor, this will return
083         *      {@link Float#MAX_VALUE} otherwise the value will always be positive
084         *      and greater than 1.
085         * 
086         *      @return The calculated peak scalar.
087         */
088        public float getVolumeScalar()
089        {
090                return this.scalar;
091        }
092}