如何增加放大AudioTrack？答案

【问题标题】：How to increase amplify AudioTrack?如何增加放大AudioTrack？
【发布时间】：2017-04-01 05:24:50
【问题描述】：

我有以下代码：

public class MainActivity extends Activity {
    private int freq = 8000;
    private AudioRecord audioRecord = null;
    private Thread Rthread = null;

    int PERMISSION_ALL = 1;
    String[] PERMISSIONS = {Manifest.permission.RECORD_AUDIO};

    private AudioTrack audioTrack = null;
    byte[] buffer = new byte[freq];
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        if(!hasPermissions(this, PERMISSIONS)){
            ActivityCompat.requestPermissions(this, PERMISSIONS, PERMISSION_ALL);
        }

        android.os.Process.setThreadPriority(android.os.Process.THREAD_PRIORITY_URGENT_AUDIO);
        final int bufferSize = AudioRecord.getMinBufferSize(freq,
                AudioFormat.CHANNEL_CONFIGURATION_MONO,
                AudioFormat.ENCODING_PCM_16BIT);


        audioRecord = new AudioRecord(MediaRecorder.AudioSource.MIC, freq,
                AudioFormat.CHANNEL_CONFIGURATION_MONO,
                MediaRecorder.AudioEncoder.AMR_NB, bufferSize);

        audioTrack = new AudioTrack(AudioManager.ROUTE_HEADSET, freq,
                AudioFormat.CHANNEL_CONFIGURATION_MONO,
                MediaRecorder.AudioEncoder.AMR_NB, bufferSize,
                AudioTrack.MODE_STREAM);

        LoudnessEnhancer enhancer = new LoudnessEnhancer(audioTrack.getAudioSessionId());

        enhancer.setTargetGain(100);
        enhancer.setEnabled(true);


        audioTrack.setPlaybackRate(freq);
        buffer = new byte[bufferSize];
        audioRecord.startRecording();
        Log.i("info", "Audio Recording started");
        audioTrack.play();
        Log.i("info", "Audio Playing started");
        Rthread = new Thread(new Runnable() {
            public void run() {
                while (true) {
                    try {
                        audioRecord.read(buffer, 0, bufferSize);
                        audioTrack.write(buffer, 0, buffer.length);

                    } catch (Throwable t) {
                        Log.e("Error", "Read write failed");
                        t.printStackTrace();
                    }
                }
            }
        });
        Rthread.start();
    }

    public static boolean hasPermissions(Context context, String... permissions) {
        if (android.os.Build.VERSION.SDK_INT >= Build.VERSION_CODES.M && context != null && permissions != null) {
            for (String permission : permissions) {
                if (ActivityCompat.checkSelfPermission(context, permission) != PackageManager.PERMISSION_GRANTED) {
                    return false;
                }
            }
        }
        return true;
    }
}

此代码能够读取来自麦克风的输入并在扬声器/连接的耳机上播放。到目前为止，一切都很好。现在，我需要放大输入的音量。我已经尝试过here 提出的解决方案，但我最终得到了真正失真的音频。我也尝试了 LoudnessEnhancer，但它似乎没有任何效果。

【问题讨论】：

音频只是一条曲线...要增加音量，您只需将曲线上的每个点乘以某个因子...例如 1.2 ...如果不够，请尝试 1.6 等...在示例中您引用的代码他使用的因子为 2，这对您的音频来说可能太多了...请注意，必须检查此拉伸并将其剪裁为由位深度定义的最大和最小允许值...在您上方的代码中没有显示你在哪里做这个点乘法......对于 16 的位深度，确保你拔出两个字节的数据来切割一个新的点，避免分别乘以每个字节......还要注意字节顺序
感谢您的快速回复！或许扭曲在这里用错了词。我的意思是音频在播放时不断中断。它不会作为连续流播放。此外，我确实需要对音频进行相当大的放大。现在，我不是音响工程师，而且我非常不擅长低级的东西，因此非常感谢您提供代码示例。

标签： android audio audiorecord audiotrack android-audiorecord

【解决方案1】：

好的，我设法让 LoudnessEnhancer 工作。我知道这是一个巨大的收益价值，但我需要在这个上获得很多收益。这是可能有类似问题的其他人的更新代码。

public class MainActivity extends Activity {
    private int freq = 8000;
    private AudioRecord audioRecord = null;
    private Thread Rthread = null;

    int PERMISSION_ALL = 1;
    String[] PERMISSIONS = {Manifest.permission.RECORD_AUDIO};

    private AudioTrack audioTrack = null;
    byte[] buffer = new byte[freq];
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        if(!hasPermissions(this, PERMISSIONS)){
            ActivityCompat.requestPermissions(this, PERMISSIONS, PERMISSION_ALL);
        }

        android.os.Process.setThreadPriority(android.os.Process.THREAD_PRIORITY_URGENT_AUDIO);
        final int bufferSize = AudioRecord.getMinBufferSize(freq,
                AudioFormat.CHANNEL_CONFIGURATION_MONO,
                AudioFormat.ENCODING_PCM_16BIT);


        audioRecord = new AudioRecord(MediaRecorder.AudioSource.MIC, freq,
                AudioFormat.CHANNEL_CONFIGURATION_MONO,
                MediaRecorder.AudioEncoder.AMR_NB, bufferSize);

        audioTrack = new AudioTrack(AudioManager.ROUTE_HEADSET, freq,
                AudioFormat.CHANNEL_CONFIGURATION_MONO,
                MediaRecorder.AudioEncoder.AMR_NB, bufferSize,
                AudioTrack.MODE_STREAM);

        LoudnessEnhancer enhancer = new LoudnessEnhancer(audioTrack.getAudioSessionId());
        NoiseSuppressor.create(audioTrack.getAudioSessionId());
        AcousticEchoCanceler.create(audioTrack.getAudioSessionId());

        enhancer.setTargetGain(10000);
        enhancer.setEnabled(true);


        audioTrack.setPlaybackRate(freq);
        buffer = new byte[bufferSize];
        audioRecord.startRecording();
        Log.i("info", "Audio Recording started");
        audioTrack.play();
        Log.i("info", "Audio Playing started");
        Rthread = new Thread(new Runnable() {
            public void run() {
                while (true) {
                    try {
                        audioRecord.read(buffer, 0, bufferSize);
                        audioTrack.write(buffer, 0, buffer.length);

                    } catch (Throwable t) {
                        Log.e("Error", "Read write failed");
                        t.printStackTrace();
                    }
                }
            }
        });
        Rthread.start();
    }

    public static boolean hasPermissions(Context context, String... permissions) {
        if (android.os.Build.VERSION.SDK_INT >= Build.VERSION_CODES.M && context != null && permissions != null) {
            for (String permission : permissions) {
                if (ActivityCompat.checkSelfPermission(context, permission) != PackageManager.PERMISSION_GRANTED) {
                    return false;
                }
            }
        }
        return true;
    }
}

【讨论】：