android – getMaxAmplitude()总是返回0

我试图以分贝表示声级压力,但我总是得到0.(TextView的输出是-Infinity但是因为log(0)= -infinity.

public class SLP extends Activity{

TextView sound;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.sound_activity);

    MediaRecorder recorder = new MediaRecorder();
    recorder.setAudioSource(MediaRecorder.AudioSource.MIC);
    recorder.setOutputFormat(MediaRecorder.OutputFormat.THREE_GPP);
    recorder.setAudioEncoder(MediaRecorder.AudioEncoder.AMR_NB);
    Timer timer = new Timer();
    timer.scheduleAtFixedRate(new RecorderTask(recorder), 0, 500);


}

private class RecorderTask extends TimerTask {
    TextView sound = (TextView) findViewById(R.id.decibel);
    private MediaRecorder recorder;

    public RecorderTask(MediaRecorder recorder) {
        this.recorder = recorder;
    }

    public void run() {
        runOnUiThread(new Runnable() {
            @Override
            public void run() {
                int amplitude = recorder.getMaxAmplitude();
                double amplitudeDb = 20 * Math.log10((double)Math.abs(amplitude) / 32768);
                sound.setText("" + amplitudeDb);
            }
        });
    }
}

Manifest.xml中的权限:

<uses-permission android:name="android.permission.RECORD_AUDIO" />

请问你能帮帮我吗?

更新

我也试过这个:

MediaRecorder recorder = new MediaRecorder();
    recorder.setAudioSource(MediaRecorder.AudioSource.MIC);
    recorder.setOutputFormat(MediaRecorder.OutputFormat.THREE_GPP);
    recorder.setAudioEncoder(MediaRecorder.AudioEncoder.AMR_NB);
    recorder.setOutputFile("/dev/null");
    try {
        recorder.prepare();
    } catch (IOException e) {
        e.printStackTrace();
    }
    recorder.start();
    Timer timer = new Timer();
    timer.scheduleAtFixedRate(new RecorderTask(recorder), 0, 500);
    recorder.reset();
}
private class RecorderTask extends TimerTask {
    TextView risultato = (TextView) findViewById(R.id.decibel);
    private MediaRecorder recorder;

    public RecorderTask(MediaRecorder recorder) {
        this.recorder = recorder;
    }

    public double getAmplitude() {
        if (recorder != null)
            return  (recorder.getMaxAmplitude());
        else
            return 0;

    }

    public void run() {
        runOnUiThread(new Runnable() {
            @Override
            public void run() {
                int amplitude = recorder.getMaxAmplitude();
                double amplitudeDb = 20 * Math.log10(getAmplitude() / 32768);
                //double db = 20 * Math.log(recorder.getMaxAmplitude() / 2700.0);
                risultato.setText("" + amplitudeDb);
            }
        });
    }
}

但没有,仍然没有 – 无限期

最佳答案
试试这个:

MediaRecorder recorder = new MediaRecorder();
    recorder.setAudioSource(MediaRecorder.AudioSource.MIC);
    recorder.setOutputFormat(MediaRecorder.OutputFormat.THREE_GPP);
    recorder.setAudioEncoder(MediaRecorder.AudioEncoder.AMR_NB);
    Timer timer = new Timer();
    timer.scheduleAtFixedRate(new RecorderTask(recorder), 0, 500);
    recorder.setOutputFile("/dev/null");

    try {
        recorder.prepare();
        recorder.start();
    } catch(IllegalStateException e)
    {
        e.printStackTrace();
    } catch (IOException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    }


}

private class RecorderTask extends TimerTask {
    TextView sound = (TextView) findViewById(R.id.decibel);
    private MediaRecorder recorder;

    public RecorderTask(MediaRecorder recorder) {
        this.recorder = recorder;
    }

    public void run() {
        runOnUiThread(new Runnable() {
            @Override
            public void run() {
                int amplitude = recorder.getMaxAmplitude();
                double amplitudeDb = 20 * Math.log10((double)Math.abs(amplitude)); 
                sound.setText("" + amplitudeDb);
            }
        });
    }
}

没有/ 32768我得到30分贝(我的沉默房间)和88分贝(当我放大声音乐时)之间的值.

我认为他们没事

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