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56 lines
1.7 KiB
56 lines
1.7 KiB
/*
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* Copyright 2010 Google Inc.
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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package com.levien.synthesizer.core.model.modules;
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import com.levien.synthesizer.core.model.CachedSignalProvider;
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import com.levien.synthesizer.core.model.SignalProvider;
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import com.levien.synthesizer.core.model.SynthesisTime;
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/**
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* A very simple low-pass filter.
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*/
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public class LowPassFilter extends CachedSignalProvider {
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/**
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* Creates a LowPassFilter with the given parameters.
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* @param source - The input signal to filter.
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* @param cutoff - "Alpha" parameter that controls the cutoff frequency.
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*/
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public LowPassFilter(SignalProvider source, SignalProvider cutoff) {
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source_ = source;
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alpha_ = cutoff;
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previousValue_ = 0.0;
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}
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public double computeValue(SynthesisTime time) {
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double alpha = alpha_.getValue(time);
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double output = 0.0;
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if (alpha != 0) {
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double signal = source_.getValue(time);
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output = previousValue_ + alpha * (signal - previousValue_);
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previousValue_ = output;
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} else {
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output = previousValue_;
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}
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return output;
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}
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// The filter parameters.
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private SignalProvider source_;
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private SignalProvider alpha_;
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private double previousValue_;
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}
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