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/*
* Copyright 2009 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.engine.MultiTable;
/**
* Sawtooth oscillator that uses multiple wave tables for band limiting. This requires more CPU than
* a plain SawtoothOscillator but has less aliasing at high frequencies.
*
* @author Phil Burk (C) 2009 Mobileer Inc
*/
public class SawtoothOscillatorBL extends UnitOscillator {
@Override
public void generate(int start, int limit) {
MultiTable multiTable = MultiTable.getInstance();
double[] frequencies = frequency.getValues();
double[] amplitudes = amplitude.getValues();
double[] outputs = output.getValues();
// Variables have a single value.
double currentPhase = phase.getValue();
double phaseIncrement = convertFrequencyToPhaseIncrement(frequencies[0]);
double positivePhaseIncrement = Math.abs(phaseIncrement);
// This is very expensive so we moved it outside the loop.
// Try to optimize it with a table lookup.
double flevel = multiTable.convertPhaseIncrementToLevel(positivePhaseIncrement);
for (int i = start; i < limit; i++) {
/* Generate sawtooth phasor to provide phase for sine generation. */
phaseIncrement = convertFrequencyToPhaseIncrement(frequencies[i]);
currentPhase = incrementWrapPhase(currentPhase, phaseIncrement);
positivePhaseIncrement = Math.abs(phaseIncrement);
double val = generateBL(multiTable, currentPhase, positivePhaseIncrement, flevel, i);
outputs[i] = val * amplitudes[i];
}
// Value needs to be saved for next time.
phase.setValue(currentPhase);
}
protected double generateBL(MultiTable multiTable, double currentPhase,
double positivePhaseIncrement, double flevel, int i) {
/* Calculate table level then use it for lookup. */
return multiTable.calculateSawtooth(currentPhase, positivePhaseIncrement, flevel);
}
}
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