| /* |
| * Copyright (C) 2015 The Android Open Source Project |
| * |
| * 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.example.android.common.midi.synth; |
| |
| /** |
| * Band limited sawtooth oscillator. |
| * This will have very little aliasing at high frequencies. |
| */ |
| public class SawOscillatorDPW extends SawOscillator { |
| private float mZ1 = 0.0f; // delayed values |
| private float mZ2 = 0.0f; |
| private float mScaler; // frequency dependent scaler |
| private final static float VERY_LOW_FREQ = 0.0000001f; |
| |
| @Override |
| public void setFrequency(float freq) { |
| /* Calculate scaling based on frequency. */ |
| freq = Math.abs(freq); |
| super.setFrequency(freq); |
| if (freq < VERY_LOW_FREQ) { |
| mScaler = (float) (0.125 * 44100 / VERY_LOW_FREQ); |
| } else { |
| mScaler = (float) (0.125 * 44100 / freq); |
| } |
| } |
| |
| @Override |
| public float render() { |
| float phase = incrementWrapPhase(); |
| /* Square the raw sawtooth. */ |
| float squared = phase * phase; |
| float diffed = squared - mZ2; |
| mZ2 = mZ1; |
| mZ1 = squared; |
| return diffed * mScaler * getAmplitude(); |
| } |
| |
| } |