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      */
pitchToFrequency(double pitch)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 
render()34     public abstract float render();
35 }
36