如何录制耳机中播放的android音频

Question

MediaRecorder class in android is used to record audio from mic, can anyone tell me how can we record audio that is actually played on headset. Sounds techy but yes it is the thing i am exploring on. I was told "Visualizer" class can record system audio but as per documentation it can only be used to visualize audio and we cannot put recorder interface there.

Read more : http://developer.android.com/reference/android/media/audiofx/Visualizer.html

Does any from below will serve the purpose ?

int CAMCORDER
int DEFAULT
int MIC
int REMOTE_SUBMIX
int VOICE_CALL
int VOICE_COMMUNICAITON
int vOICE_DOWNLINK
int VOICE_RECOGNITION
int VOICE_UPLINK

Has anyone worked on OpenSLES? Heard that too serves the purpose of it

If there any Android APIs or Third Party APIs you have come across please feel free to share info. Few blogs also say this can be done at NDK level. If anyone has worked on it or do have code examples kindly inform

Thanks

Example Code to show Michael :

public class VisualizerView extends View {
  private static final String TAG = "VisualizerView";

  private byte[] mBytes;
  private byte[] mFFTBytes;
  private Rect mRect = new Rect();
  private Visualizer mVisualizer;

  private Set<Renderer> mRenderers;

  private Paint mFlashPaint = new Paint();
  private Paint mFadePaint = new Paint();
  private ByteArrayOutputStream buffer;

  public VisualizerView(Context context, AttributeSet attrs, int defStyle)
  {
    super(context, attrs);
    init();
  }

  public VisualizerView(Context context, AttributeSet attrs)
  {
    this(context, attrs, 0);
  }

  public VisualizerView(Context context)
  {
    this(context, null, 0);
  }

  private void init() {
    mBytes = null;
    mFFTBytes = null;

    mFlashPaint.setColor(Color.argb(122, 255, 255, 255));
    mFadePaint.setColor(Color.argb(238, 255, 255, 255)); // Adjust alpha to change how quickly the image fades
    mFadePaint.setXfermode(new PorterDuffXfermode(Mode.MULTIPLY));

    mRenderers = new HashSet<Renderer>();
  }

  /**
   * Links the visualizer to a player
   * @param player - MediaPlayer instance to link to
   */
  public void link(MediaPlayer player)
  {
    if(player == null)
    {
      throw new NullPointerException("Cannot link to null MediaPlayer");
    }

    // Create the Visualizer object and attach it to our media player.
    mVisualizer = new Visualizer(player.getAudioSessionId());
    mVisualizer.setCaptureSize(Visualizer.getCaptureSizeRange()[1]);

    // Pass through Visualizer data to VisualizerView
    Visualizer.OnDataCaptureListener captureListener = new Visualizer.OnDataCaptureListener()
    {
      @Override
      public void onWaveFormDataCapture(Visualizer visualizer, byte[] bytes,
          int samplingRate)
      {
        updateVisualizer(bytes);
        //Record
        if (bytes.length>-1)
        buffer.write(bytes, 0, bytes.length);
        //Record ends
      }

      @Override
      public void onFftDataCapture(Visualizer visualizer, byte[] bytes,
          int samplingRate)
      {
        updateVisualizerFFT(bytes);
      }
    };

    mVisualizer.setDataCaptureListener(captureListener,
        Visualizer.getMaxCaptureRate() / 2, true, true);

    // Enabled Visualizer and disable when we're done with the stream
    mVisualizer.setEnabled(true);
    player.setOnCompletionListener(new MediaPlayer.OnCompletionListener()
    {
      @Override
      public void onCompletion(MediaPlayer mediaPlayer)
      {
        mVisualizer.setEnabled(false);

        //Save File
        try {
            buffer.flush();
        } catch (IOException e) {
            e.printStackTrace();
        }
        mBytes = buffer.toByteArray();
        try {
            buffer.close();
        } catch (IOException e) {
            e.printStackTrace();
        }
        mVisualizer.release();

        File file = new File(Environment.getExternalStorageDirectory(), "music1.wav");
        FileOutputStream fos;

        try {
            fos = new FileOutputStream(file);
            fos.write(mBytes);
            fos.flush();
            fos.close();
        } catch (FileNotFoundException e) {
            // handle exception
        } catch (IOException e) {
            // handle exception
        }
        //Save File ends

      }
    });
  }

  public void addRenderer(Renderer renderer)
  {
    if(renderer != null)
    {
      mRenderers.add(renderer);
    }
  }

  public void clearRenderers()
  {
    mRenderers.clear();
  }

  /**
   * Call to release the resources used by VisualizerView. Like with the
   * MediaPlayer it is good practice to call this method
   */
  public void release()
  {
    mVisualizer.release();
  }

  /**
   * Pass data to the visualizer. Typically this will be obtained from the
   * Android Visualizer.OnDataCaptureListener call back. See
   * {@link Visualizer.OnDataCaptureListener#onWaveFormDataCapture }
   * @param bytes
   */
  public void updateVisualizer(byte[] bytes) {
    mBytes = bytes;
    invalidate();
  }

  /**
   * Pass FFT data to the visualizer. Typically this will be obtained from the
   * Android Visualizer.OnDataCaptureListener call back. See
   * {@link Visualizer.OnDataCaptureListener#onFftDataCapture }
   * @param bytes
   */
  public void updateVisualizerFFT(byte[] bytes) {
    mFFTBytes = bytes;
    invalidate();
  }

  boolean mFlash = false;

  /**
   * Call this to make the visualizer flash. Useful for flashing at the start
   * of a song/loop etc...
   */
  public void flash() {
    mFlash = true;
    invalidate();
  }

  Bitmap mCanvasBitmap;
  Canvas mCanvas;


  @Override
  protected void onDraw(Canvas canvas) {
    super.onDraw(canvas);

    // Create canvas once we're ready to draw
    mRect.set(0, 0, getWidth(), getHeight());

    if(mCanvasBitmap == null)
    {
      mCanvasBitmap = Bitmap.createBitmap(canvas.getWidth(), canvas.getHeight(), Config.ARGB_8888);
    }
    if(mCanvas == null)
    {
      mCanvas = new Canvas(mCanvasBitmap);
    }

    if (mBytes != null) {
      // Render all audio renderers
      AudioData audioData = new AudioData(mBytes);
      for(Renderer r : mRenderers)
      {
        r.render(mCanvas, audioData, mRect);
      }
    }

    if (mFFTBytes != null) {
      // Render all FFT renderers
      FFTData fftData = new FFTData(mFFTBytes);
      for(Renderer r : mRenderers)
      {
        r.render(mCanvas, fftData, mRect);
      }
    }

    // Fade out old contents
    mCanvas.drawPaint(mFadePaint);

    if(mFlash)
    {
      mFlash = false;
      mCanvas.drawPaint(mFlashPaint);
    }

    canvas.drawBitmap(mCanvasBitmap, new Matrix(), null);
  }
}

Answer 1

can anyone tell me how can we record audio that is actually played on headset.

You can't, as there's no official support in the Android APIs to do that. Doesn't matter if you use the Java APIs, or the native APIs included in the NDK.
There may be hacks that work on specific devices, if you've got root access, etc, but I'm not going to cover those. If you're interested you can try searching and see what you can come up with.

---

I was told "Visualizer" class can record system audio but as per documentation it can only be used to visualize audio and we cannot put recorder interface there.

The Visualizer has this method:

public int getWaveForm (byte[] waveform)

Returns a waveform capture of currently playing audio content. The capture consists in a number of consecutive 8-bit (unsigned) mono PCM samples equal to the capture size returned by getCaptureSize() .

So you can record the currently playing audio using the Visualizer . But as is mentioned in the description above, you'll only get low-quality audio data, because the purpose of this method is to get audio data that you can use for visualization purposes, not for general recording purposes.