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/*
* Copyright 2014 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;
/**
* PhaseShifter effects processor. This unit emulates a common guitar pedal effect but without the
* LFO modulation. You can use your own modulation source connected to the "offset" port. Different
* frequencies are phase shifted varying amounts using a series of AllPass filters. By feeding the
* output back to the input we can get varying phase cancellation. This implementation was based on
* code posted to the music-dsp archive by Ross Bencina. http://www.musicdsp.org/files/phaser.cpp
*
* @author (C) 2014 Phil Burk, Mobileer Inc
* @see FilterLowPass
* @see FilterAllPass
* @see RangeConverter
*/
public class PhaseShifter extends UnitFilter {
/**
* Connect an oscillator to this port to sweep the phase. A range of 0.05 to 0.4 is a good
* start.
*/
public UnitInputPort offset;
public UnitInputPort feedback;
public UnitInputPort depth;
private double zm1;
private double[] xs;
private double[] ys;
public PhaseShifter() {
this(6);
}
public PhaseShifter(int numStages) {
addPort(offset = new UnitInputPort("Offset", 0.1));
addPort(feedback = new UnitInputPort("Feedback", 0.7));
addPort(depth = new UnitInputPort("Depth", 1.0));
xs = new double[numStages];
ys = new double[numStages];
}
@Override
public void generate(int start, int limit) {
double[] inputs = input.getValues();
double[] outputs = output.getValues();
double[] feedbacks = feedback.getValues();
double[] depths = depth.getValues();
double[] offsets = offset.getValues();
double gain;
for (int i = start; i < limit; i++) {
// Support audio rate modulation.
double currentOffset = offsets[i];
// Prevent gain from exceeding 1.0.
gain = 1.0 - (currentOffset * currentOffset);
if (gain < -1.0) {
gain = -1.0;
}
double x = inputs[i] + (zm1 * feedbacks[i]);
// Cascaded all-pass filters.
for (int stage = 0; stage < xs.length; stage++) {
double temp = ys[stage] = (gain * (ys[stage] - x)) + xs[stage];
xs[stage] = x;
x = temp;
}
zm1 = x;
outputs[i] = inputs[i] + (x * depths[i]);
}
}
}
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