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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;
import com.jsyn.ports.UnitOutputPort;
import com.jsyn.ports.UnitVariablePort;
/**
* Tracks the peaks of an input signal. This can be used to monitor the overall amplitude of a
* signal. The output can be used to drive color organs, vocoders, VUmeters, etc. Output drops
* exponentially when the input drops below the current output level. The output approaches zero
* based on the value on the halfLife port.
*
* @author (C) 1997-2009 Phil Burk, SoftSynth.com
*/
public class PeakFollower extends UnitGenerator {
public UnitInputPort input;
public UnitVariablePort current;
public UnitInputPort halfLife;
public UnitOutputPort output;
private double previousHalfLife = -1.0;
private double decayScalar = 0.99;
/* Define Unit Ports used by connect() and set(). */
public PeakFollower() {
addPort(input = new UnitInputPort("Input"));
addPort(halfLife = new UnitInputPort(1, "HalfLife", 0.1));
addPort(current = new UnitVariablePort("Current"));
addPort(output = new UnitOutputPort("Output"));
}
@Override
public void generate(int start, int limit) {
double[] inputs = input.getValues();
double[] outputs = output.getValues();
double currentHalfLife = halfLife.getValues()[0];
double currentValue = current.getValue();
if (currentHalfLife != previousHalfLife) {
decayScalar = this.convertHalfLifeToMultiplier(currentHalfLife);
previousHalfLife = currentHalfLife;
}
double scalar = 1.0 - decayScalar;
for (int i = start; i < limit; i++) {
double inputValue = inputs[i];
if (inputValue < 0.0) {
inputValue = -inputValue; // absolute value
}
if (inputValue >= currentValue) {
currentValue = inputValue;
} else {
currentValue = currentValue * scalar;
}
outputs[i] = currentValue;
}
/*
* When current gets close to zero, set current to zero to prevent FP underflow, which can
* cause a severe performance degradation in 'C'.
*/
if (currentValue < VERY_SMALL_FLOAT) {
currentValue = 0.0;
}
current.setValue(currentValue);
}
}
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