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/*
* Copyright 1997 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.unitgen;
import com.jsyn.ports.UnitInputPort;
/**
* InterpolatingDelay
* <P>
* InterpolatingDelay provides a variable time delay with an input and output. The internal data
* format is 32-bit floating point. The amount of delay can be varied from 0.0 to a time in seconds
* corresponding to the numFrames allocated. The fractional delay values are calculated by linearly
* interpolating between adjacent values in the delay line.
* <P>
* This unit can be used to implement time varying delay effects such as a flanger or a chorus. It
* can also be used to implement physical models of acoustic instruments, or other tunable delay
* based resonant systems.
* <P>
*
* @author (C) 1997-2011 Phil Burk, Mobileer Inc
* @see Delay
*/
public class InterpolatingDelay extends UnitFilter {
/**
* Delay time in seconds. This value will converted to frames and clipped between zero and the
* numFrames value passed to allocate(). The minimum and default delay time is 0.0.
*/
public UnitInputPort delay;
private float[] buffer;
private int cursor;
private int numFrames;
public InterpolatingDelay() {
addPort(delay = new UnitInputPort("Delay"));
}
/**
* Allocate memory for the delay buffer. For a 2 second delay at 44100 Hz sample rate you will
* need at least 88200 samples.
*
* @param numFrames size of the float array to hold the delayed samples
*/
public void allocate(int numFrames) {
this.numFrames = numFrames;
// Allocate extra frame for guard point to speed up interpolation.
buffer = new float[numFrames + 1];
}
@Override
public void generate(int start, int limit) {
double[] inputs = input.getValues();
double[] outputs = output.getValues();
double[] delays = delay.getValues();
for (int i = start; i < limit; i++) {
// This should be at the beginning of the loop
// because the guard point should == buffer[0].
if (cursor == numFrames) {
// Write guard point! Must allocate one extra sample.
buffer[numFrames] = (float) inputs[i];
cursor = 0;
}
buffer[cursor] = (float) inputs[i];
/* Convert delay time to a clipped frame offset. */
double delayFrames = delays[i] * getFrameRate();
// Clip to zero delay.
if (delayFrames <= 0.0) {
outputs[i] = buffer[cursor];
} else {
// Clip to maximum delay.
if (delayFrames >= numFrames) {
delayFrames = numFrames - 1;
}
// Calculate fractional index into delay buffer.
double readIndex = cursor - delayFrames;
if (readIndex < 0.0) {
readIndex += numFrames;
}
// setup for interpolation.
// We know readIndex is > 0 so we do not need to call floor().
int iReadIndex = (int) readIndex;
double frac = readIndex - iReadIndex;
// Get adjacent values relying on guard point to prevent overflow.
double val0 = buffer[iReadIndex];
double val1 = buffer[iReadIndex + 1];
// Interpolate new value.
outputs[i] = val0 + (frac * (val1 - val0));
}
cursor += 1;
}
}
}
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