1 /* 2 * Copyright (C) 2015 The Android Open Source Project 3 * 4 * Licensed under the Apache License, Version 2.0 (the "License"); 5 * you may not use this file except in compliance with the License. 6 * You may obtain a copy of the License at 7 * 8 * http://www.apache.org/licenses/LICENSE-2.0 9 * 10 * Unless required by applicable law or agreed to in writing, software 11 * distributed under the License is distributed on an "AS IS" BASIS, 12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 13 * See the License for the specific language governing permissions and 14 * limitations under the License. 15 */ 16 17 package com.example.android.common.midi.synth; 18 19 public abstract class SynthUnit { 20 21 private static final double CONCERT_A_PITCH = 69.0; 22 private static final double CONCERT_A_FREQUENCY = 440.0; 23 24 /** 25 * @param pitch 26 * MIDI pitch in semitones 27 * @return frequency 28 */ 29 public static double pitchToFrequency(double pitch) { 30 double semitones = pitch - CONCERT_A_PITCH; 31 return CONCERT_A_FREQUENCY * Math.pow(2.0, semitones / 12.0); 32 } 33 34 public abstract float render(); 35 } 36
