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/*
* Copyright 2010 Phil Burk, Mobileer Inc
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package com.jsyn.data;
import com.jsyn.exceptions.ChannelMismatchException;
/**
* Evaluate a Function by interpolating between the values in a table. This can be used for
* wavetable lookup or waveshaping.
*
* @author Phil Burk (C) 2010 Mobileer Inc
*/
public class DoubleTable implements Function {
private double[] table;
public DoubleTable(int numFrames) {
allocate(numFrames);
}
public DoubleTable(double[] data) {
allocate(data.length);
write(data);
}
public DoubleTable(ShortSample shortSample) {
if (shortSample.getChannelsPerFrame() != 1) {
throw new ChannelMismatchException("DoubleTable can only be built from mono samples.");
}
short[] buffer = new short[256];
int framesLeft = shortSample.getNumFrames();
allocate(framesLeft);
int cursor = 0;
while (framesLeft > 0) {
int numTransfer = framesLeft;
if (numTransfer > buffer.length) {
numTransfer = buffer.length;
}
shortSample.read(cursor, buffer, 0, numTransfer);
write(cursor, buffer, 0, numTransfer);
cursor += numTransfer;
framesLeft -= numTransfer;
}
}
public void allocate(int numFrames) {
table = new double[numFrames];
}
public void write(double[] data) {
write(0, data, 0, data.length);
}
public void write(int startFrame, short[] data, int startIndex, int numFrames) {
for (int i = 0; i < numFrames; i++) {
table[startFrame + i] = data[startIndex + i] * (1.0 / 32768.0);
}
}
public void write(int startFrame, double[] data, int startIndex, int numFrames) {
for (int i = 0; i < numFrames; i++) {
table[startFrame + i] = data[startIndex + i];
}
}
/**
* Treat the double array as a lookup table with a domain of -1.0 to 1.0. If the input is out of
* range then the output will clip to the end values.
*
* @param input
* @return interpolated value from table
*/
@Override
public double evaluate(double input) {
double interp;
if (input < -1.0) {
interp = table[0];
} else if (input < 1.0) {
double fractionalIndex = (table.length - 1) * (input - (-1.0)) / 2.0;
// We don't need floor() because fractionalIndex >= 0.0
int index = (int) fractionalIndex;
double fraction = fractionalIndex - index;
double s1 = table[index];
double s2 = table[index + 1];
interp = ((s2 - s1) * fraction) + s1;
} else {
interp = table[table.length - 1];
}
return interp;
}
}
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