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 has
044 * currently been calculated for the stream which has passed. This will only
045 * return the correct value for the whole audio stream once the whole audio
046 * stream has passed through the processor. This processor will not perform
047 * attenuation - that is, the volume scalar will always be greater than 1 (and
048 * 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 peak
052 * 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         * 
066         * @see org.openimaj.audio.processor.AudioProcessor#process(org.openimaj.audio.SampleChunk)
067         */
068        @Override
069        public SampleChunk process(final SampleChunk sample) throws Exception
070        {
071                // This allows us to retrieve samples that are scaled to 0..1 float
072                // values
073                final SampleBuffer sb = sample.getSampleBuffer();
074
075                for (final float s : sb)
076                        if (Math.abs(s) * this.scalar > 1)
077                                this.scalar = 1 / Math.abs(s);
078
079                return sample;
080        }
081
082        /**
083         * Returns the calculated peak scalar as it currently stands in the stream.
084         * If no audio has passed through the processor, this will return
085         * {@link Float#MAX_VALUE} otherwise the value will always be positive and
086         * greater than 1.
087         *
088         * @return The calculated peak scalar.
089         */
090        public float getVolumeScalar()
091        {
092                return this.scalar;
093        }
094}