common/src/java/com/example/android/common/midi/synth/SynthUnit.java

/*
 * 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;

public abstract class SynthUnit {

    private static final double CONCERT_A_PITCH = 69.0;
    private static final double CONCERT_A_FREQUENCY = 440.0;

    /**
     * @param pitch
     *            MIDI pitch in semitones
     * @return frequency
     */
    public static double pitchToFrequency(double pitch) {
        double semitones = pitch - CONCERT_A_PITCH;
        return CONCERT_A_FREQUENCY * Math.pow(2.0, semitones / 12.0);
    }

    public abstract float render();
}