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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 /**
     20  * Base class for a polyphonic synthesizer voice.
     21  */
     22 public abstract class SynthVoice {
     23     private int mNoteIndex;
     24     private float mAmplitude;
     25     public static final int STATE_OFF = 0;
     26     public static final int STATE_ON = 1;
     27     private int mState = STATE_OFF;
     28 
     29     public SynthVoice() {
     30         mNoteIndex = -1;
     31     }
     32 
     33     public void noteOn(int noteIndex, int velocity) {
     34         mState = STATE_ON;
     35         this.mNoteIndex = noteIndex;
     36         setAmplitude(velocity / 128.0f);
     37     }
     38 
     39     public void noteOff() {
     40         mState = STATE_OFF;
     41     }
     42 
     43     /**
     44      * Add the output of this voice to an output buffer.
     45      *
     46      * @param outputBuffer
     47      * @param samplesPerFrame
     48      * @param level
     49      */
     50     public void mix(float[] outputBuffer, int samplesPerFrame, float level) {
     51         int numFrames = outputBuffer.length / samplesPerFrame;
     52         for (int i = 0; i < numFrames; i++) {
     53             float output = render();
     54             int offset = i * samplesPerFrame;
     55             for (int jf = 0; jf < samplesPerFrame; jf++) {
     56                 outputBuffer[offset + jf] += output * level;
     57             }
     58         }
     59     }
     60 
     61     public abstract float render();
     62 
     63     public boolean isDone() {
     64         return mState == STATE_OFF;
     65     }
     66 
     67     public int getNoteIndex() {
     68         return mNoteIndex;
     69     }
     70 
     71     public float getAmplitude() {
     72         return mAmplitude;
     73     }
     74 
     75     public void setAmplitude(float amplitude) {
     76         this.mAmplitude = amplitude;
     77     }
     78 
     79     /**
     80      * @param scaler
     81      */
     82     public void setFrequencyScaler(float scaler) {
     83     }
     84 
     85 }
     86