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      1 /*
      2  * Copyright (C) 2016 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 org.drrickorang.loopback;
     18 
     19 import android.content.Context;
     20 import android.media.AudioManager;
     21 import android.os.Handler;
     22 import android.os.Looper;
     23 import android.util.Log;
     24 
     25 class SoundLevelCalibration {
     26     private static final int SECONDS_PER_LEVEL = 1;
     27     private static final int MAX_STEPS = 15; // The maximum number of levels that should be tried
     28     private static final double CRITICAL_RATIO = 0.41; // Ratio of input over output amplitude at
     29                                                       // which the feedback loop neither decays nor
     30                                                       // grows (determined experimentally)
     31     private static final String TAG = "SoundLevelCalibration";
     32 
     33     private NativeAudioThread mNativeAudioThread = null;
     34     private AudioManager mAudioManager;
     35 
     36     private SoundLevelChangeListener mChangeListener;
     37 
     38     abstract static class SoundLevelChangeListener {
     39         // used to run the callback on the UI thread
     40         private Handler handler = new Handler(Looper.getMainLooper());
     41 
     42         abstract void onChange(int newLevel);
     43 
     44         private void go(final int newLevel) {
     45             handler.post(new Runnable() {
     46                 @Override
     47                 public void run() {
     48                     onChange(newLevel);
     49                 }
     50             });
     51         }
     52     }
     53 
     54     SoundLevelCalibration(int samplingRate, int playerBufferSizeInBytes,
     55                                  int recorderBufferSizeInBytes, int micSource, int performanceMode, Context context) {
     56 
     57         // TODO: Allow capturing wave data without doing glitch detection.
     58         CaptureHolder captureHolder = new CaptureHolder(0, "", false, false, false, context,
     59                 samplingRate);
     60         // TODO: Run for less than 1 second.
     61         mNativeAudioThread = new NativeAudioThread(samplingRate, playerBufferSizeInBytes,
     62                 recorderBufferSizeInBytes, micSource, performanceMode,
     63                 Constant.LOOPBACK_PLUG_AUDIO_THREAD_TEST_TYPE_BUFFER_PERIOD, SECONDS_PER_LEVEL,
     64                 SECONDS_PER_LEVEL, 0, captureHolder);
     65         mAudioManager = (AudioManager) context.getSystemService(Context.AUDIO_SERVICE);
     66     }
     67 
     68     // TODO: Allow stopping in the middle of calibration
     69     int calibrate() {
     70         final int maxLevel = mAudioManager.getStreamMaxVolume(AudioManager.STREAM_MUSIC);
     71         int levelBottom = 0;
     72         int levelTop = maxLevel + 1;
     73         while(levelTop - levelBottom > 1) {
     74             int level = (levelBottom + levelTop) / 2;
     75             Log.d(TAG, "setting level to " + level);
     76             setVolume(level);
     77 
     78             double amplitude = runAudioThread(mNativeAudioThread);
     79             mNativeAudioThread = new NativeAudioThread(mNativeAudioThread); // generate fresh thread
     80             Log.d(TAG, "calibrate: at sound level " + level + " volume was " + amplitude);
     81 
     82             if (amplitude < Constant.SINE_WAVE_AMPLITUDE * CRITICAL_RATIO) {
     83                 levelBottom = level;
     84             } else {
     85                 levelTop = level;
     86             }
     87         }
     88         // At this point, levelBottom has the highest proper value, if there is one (0 otherwise)
     89         Log.d(TAG, "Final level: " + levelBottom);
     90         setVolume(levelBottom);
     91         return levelBottom;
     92     }
     93 
     94     private double runAudioThread(NativeAudioThread thread) {
     95         // runs the native audio thread and returns the average amplitude
     96         thread.start();
     97         try {
     98             thread.join();
     99         } catch (InterruptedException e) {
    100             e.printStackTrace();
    101         }
    102         double[] data = thread.getWaveData();
    103         return averageAmplitude(data);
    104     }
    105 
    106     // TODO: Only gives accurate results for an undistorted sine wave. Check for distortion.
    107     private static double averageAmplitude(double[] data) {
    108         if (data == null || data.length == 0) {
    109             return 0; // no data is present
    110         }
    111         double sumSquare = 0;
    112         for (double x : data) {
    113             sumSquare += x * x;
    114         }
    115         return Math.sqrt(2.0 * sumSquare / data.length); // amplitude of the sine wave
    116     }
    117 
    118     private void setVolume(int level) {
    119         mAudioManager.setStreamVolume(AudioManager.STREAM_MUSIC, level, 0);
    120         if (mChangeListener != null) {
    121             mChangeListener.go(level);
    122         }
    123     }
    124 
    125     void setChangeListener(SoundLevelChangeListener changeListener) {
    126         mChangeListener = changeListener;
    127     }
    128 }
    129