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.conversion; 034 035import org.openimaj.audio.AudioFormat; 036import org.openimaj.audio.AudioStream; 037import org.openimaj.audio.SampleChunk; 038import org.openimaj.audio.processor.AudioProcessor; 039import org.openimaj.audio.samples.SampleBuffer; 040import org.openimaj.audio.samples.SampleBufferFactory; 041import org.openimaj.math.util.Interpolation; 042 043/** 044 * A sample rate conversion audio processing class. There is an enumerator 045 * within the class that is publically available for determining the 046 * algorithm for sample rate conversion. This defaults to 047 * {@link SampleRateConversionAlgorithm#LINEAR_INTERPOLATION}. 048 * <p> 049 * To use the class, instantiate using the default constructor or the 050 * chainable constructor. Both of these constructors take the algorithm for 051 * sample rate conversion as well as the output format. The output format 052 * must have the same number of bits and same number of channels as the 053 * expected input otherwise the {@link #process(SampleChunk)} method 054 * will throw {@link IllegalArgumentException}. The input format for the samples 055 * is expected to be provided as part of the {@link SampleChunk}. 056 * <p> 057 * The class itself checks whether the output format and the input format 058 * are the same (in which case the sample does not need to be resampled). 059 * That means the algorithm implementation does not need to do this. 060 * 061 * @author David Dupplaw (dpd@ecs.soton.ac.uk) 062 * 063 * @created 18 Jun 2012 064 */ 065public class SampleRateConverter extends AudioProcessor 066{ 067 /** 068 * An enumerator of the different sample rate conversion algorithms 069 * available in this sample rate converter. 070 * 071 * @author David Dupplaw (dpd@ecs.soton.ac.uk) 072 * 073 * @created 18 Jun 2012 074 */ 075 public enum SampleRateConversionAlgorithm 076 { 077 /** 078 * Performs linear interpolation between samples where the sample rate 079 * in the output format is greater than the sample rate of the input 080 * format. If the sample rate is less, then the nearest value 081 * of the input samples is used. 082 */ 083 LINEAR_INTERPOLATION 084 { 085 @Override 086 public SampleChunk process( final SampleChunk s, final AudioFormat output) 087 { 088 final AudioFormat input = s.getFormat(); 089 090 // Check to see if the input and output are the same 091 if( input.getSampleRateKHz() == output.getSampleRateKHz() ) 092 return s; 093 094 // Work out the size of the output sample chunk 095 final double scalar = input.getSampleRateKHz() / output.getSampleRateKHz(); 096 final SampleBuffer sbin = s.getSampleBuffer(); 097 final double size = sbin.size() / scalar; 098 099 if( this.sbout == null || this.sbout.size() != (int)size ) 100 { 101 this.sbout = SampleBufferFactory.createSampleBuffer( 102 output, (int)size ); 103 this.sbout.setFormat( output ); 104 } 105 106 // If the input format has a greater sample rate than the 107 // output format - down sampling (scalar > 1) 108 if( scalar > 1 ) 109 { 110 for( int i = 0; i < this.sbout.size(); i++ ) 111 this.sbout.set( i, sbin.get( (int)(i * scalar) ) ); 112 return this.sbout.getSampleChunk(); 113 } 114 // If the input format has a sample rate less than that 115 // of the output - up sampling (scalar < 1) 116 else 117 { 118 // Linear interpolate each sample value 119 for( int i = 0; i < this.sbout.size()-1; i++ ) 120 { 121 final int inputSampleX = (int)(i * scalar); 122 this.sbout.set( i, Interpolation.lerp( (float)(i*scalar), 123 inputSampleX, sbin.get(inputSampleX), 124 inputSampleX+1, sbin.get(inputSampleX+1) ) ); 125 } 126 this.sbout.set( this.sbout.size()-1, sbin.get(sbin.size()-1) ); 127 return this.sbout.getSampleChunk(); 128 } 129 } 130 }; 131 132 protected SampleBuffer sbout = null; 133 134 /** 135 * Process a sample chunk and output a sample chunk in the given 136 * output format. 137 * 138 * @param s The input sample chunk 139 * @param output The output format 140 * @return A resampled sample chunk. 141 */ 142 public abstract SampleChunk process( SampleChunk s, AudioFormat output ); 143 } 144 145 /** 146 * Sample rate conversion defaults to 147 * {@link SampleRateConversionAlgorithm#LINEAR_INTERPOLATION} 148 */ 149 private SampleRateConversionAlgorithm sampleConverter = 150 SampleRateConversionAlgorithm.LINEAR_INTERPOLATION; 151 152 /** The output format to which sample chunks will be converted */ 153 private AudioFormat outputFormat = null; 154 155 /** 156 * Default constructor that takes the input conversion 157 * @param converter The converter to use 158 * @param outputFormat The output format to convert to 159 */ 160 public SampleRateConverter( final SampleRateConversionAlgorithm converter, 161 final AudioFormat outputFormat ) 162 { 163 this.sampleConverter = converter; 164 this.outputFormat = outputFormat; 165 this.setFormat( outputFormat ); 166 } 167 168 /** 169 * Chainable constructor. 170 * 171 * @param as The audio stream to process 172 * @param converter The converter to use 173 * @param outputFormat The output format to convert to 174 */ 175 public SampleRateConverter( final AudioStream as, final SampleRateConversionAlgorithm converter, 176 final AudioFormat outputFormat ) 177 { 178 super( as ); 179 this.sampleConverter = converter; 180 this.outputFormat = outputFormat; 181 this.setFormat( outputFormat ); 182 } 183 184 /** 185 * {@inheritDoc} 186 * @see org.openimaj.audio.processor.AudioProcessor#process(org.openimaj.audio.SampleChunk) 187 */ 188 @Override 189 public SampleChunk process( final SampleChunk sample ) throws Exception 190 { 191 if( sample.getFormat().getNBits() != this.outputFormat.getNBits() ) 192 throw new IllegalArgumentException( "The number of bits in the " + 193 "output format is not the same as the sample chunk. Use a " + 194 "resampling conversion first before using the sample-rate " + 195 "converter." ); 196 197 if( sample.getFormat().getNumChannels() != this.outputFormat.getNumChannels() ) 198 throw new IllegalArgumentException( "The number of channels in the " + 199 "output format is not the same as the sample chunk. Use a " + 200 "channel converter first before using the sample-rate " + 201 "converter." ); 202 203 if( sample.getFormat().getSampleRateKHz() == this.outputFormat.getSampleRateKHz() ) 204 return sample; 205 206 final SampleChunk sc = this.sampleConverter.process( sample, this.outputFormat ); 207 sc.setStartTimecode( sample.getStartTimecode() ); 208 return sc; 209 } 210}