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      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