The audio session ID passed to the constructor indicates which audio content should be
* visualized:
*
Two types of representation of audio content can be captured:
*
The length of the capture can be retrieved or specified by calling respectively * {@link #getCaptureSize()} and {@link #setCaptureSize(int)} methods. The capture size must be a * power of 2 in the range returned by {@link #getCaptureSizeRange()}. *
In addition to the polling capture mode described above with {@link #getWaveForm(byte[])} and * {@link #getFft(byte[])} methods, a callback mode is also available by installing a listener by * use of the {@link #setDataCaptureListener(OnDataCaptureListener, int, boolean, boolean)} method. * The rate at which the listener capture method is called as well as the type of data returned is * specified. *
Before capturing data, the Visualizer must be enabled by calling the * {@link #setEnabled(boolean)} method. * When data capture is not needed any more, the Visualizer should be disabled. *
It is good practice to call the {@link #release()} method when the Visualizer is not used * anymore to free up native resources associated to the Visualizer instance. *
Creating a Visualizer on the output mix (audio session 0) requires permission * {@link android.Manifest.permission#MODIFY_AUDIO_SETTINGS} *
The Visualizer class can also be used to perform measurements on the audio being played back.
* The measurements to perform are defined by setting a mask of the requested measurement modes with
* {@link #setMeasurementMode(int)}. Supported values are {@link #MEASUREMENT_MODE_NONE} to cancel
* any measurement, and {@link #MEASUREMENT_MODE_PEAK_RMS} for peak and RMS monitoring.
* Measurements can be retrieved through {@link #getMeasurementPeakRms(MeasurementPeakRms)}.
*/
public class Visualizer {
static {
System.loadLibrary("audioeffect_jni");
native_init();
}
private final static String TAG = "Visualizer-JAVA";
/**
* State of a Visualizer object that was not successfully initialized upon creation
*/
public static final int STATE_UNINITIALIZED = 0;
/**
* State of a Visualizer object that is ready to be used.
*/
public static final int STATE_INITIALIZED = 1;
/**
* State of a Visualizer object that is active.
*/
public static final int STATE_ENABLED = 2;
// to keep in sync with system/media/audio_effects/include/audio_effects/effect_visualizer.h
/**
* Defines a capture mode where amplification is applied based on the content of the captured
* data. This is the default Visualizer mode, and is suitable for music visualization.
*/
public static final int SCALING_MODE_NORMALIZED = 0;
/**
* Defines a capture mode where the playback volume will affect (scale) the range of the
* captured data. A low playback volume will lead to low sample and fft values, and vice-versa.
*/
public static final int SCALING_MODE_AS_PLAYED = 1;
/**
* Defines a measurement mode in which no measurements are performed.
*/
public static final int MEASUREMENT_MODE_NONE = 0;
/**
* Defines a measurement mode which computes the peak and RMS value in mB, where 0mB is the
* maximum sample value, and -9600mB is the minimum value.
* Values for peak and RMS can be retrieved with
* {@link #getMeasurementPeakRms(MeasurementPeakRms)}.
*/
public static final int MEASUREMENT_MODE_PEAK_RMS = 1 << 0;
// to keep in sync with frameworks/base/media/jni/audioeffect/android_media_Visualizer.cpp
private static final int NATIVE_EVENT_PCM_CAPTURE = 0;
private static final int NATIVE_EVENT_FFT_CAPTURE = 1;
private static final int NATIVE_EVENT_SERVER_DIED = 2;
// Error codes:
/**
* Successful operation.
*/
public static final int SUCCESS = 0;
/**
* Unspecified error.
*/
public static final int ERROR = -1;
/**
* Internal operation status. Not returned by any method.
*/
public static final int ALREADY_EXISTS = -2;
/**
* Operation failed due to bad object initialization.
*/
public static final int ERROR_NO_INIT = -3;
/**
* Operation failed due to bad parameter value.
*/
public static final int ERROR_BAD_VALUE = -4;
/**
* Operation failed because it was requested in wrong state.
*/
public static final int ERROR_INVALID_OPERATION = -5;
/**
* Operation failed due to lack of memory.
*/
public static final int ERROR_NO_MEMORY = -6;
/**
* Operation failed due to dead remote object.
*/
public static final int ERROR_DEAD_OBJECT = -7;
//--------------------------------------------------------------------------
// Member variables
//--------------------
/**
* Indicates the state of the Visualizer instance
*/
private int mState = STATE_UNINITIALIZED;
/**
* Lock to synchronize access to mState
*/
private final Object mStateLock = new Object();
/**
* System wide unique Identifier of the visualizer engine used by this Visualizer instance
*/
private int mId;
/**
* Lock to protect listeners updates against event notifications
*/
private final Object mListenerLock = new Object();
/**
* Handler for events coming from the native code
*/
private NativeEventHandler mNativeEventHandler = null;
/**
* PCM and FFT capture listener registered by client
*/
private OnDataCaptureListener mCaptureListener = null;
/**
* Server Died listener registered by client
*/
private OnServerDiedListener mServerDiedListener = null;
// accessed by native methods
private long mNativeVisualizer;
private long mJniData;
//--------------------------------------------------------------------------
// Constructor, Finalize
//--------------------
/**
* Class constructor.
* @param audioSession system wide unique audio session identifier. If audioSession
* is not 0, the visualizer will be attached to the MediaPlayer or AudioTrack in the
* same audio session. Otherwise, the Visualizer will apply to the output mix.
*
* @throws java.lang.UnsupportedOperationException
* @throws java.lang.RuntimeException
*/
public Visualizer(int audioSession)
throws UnsupportedOperationException, RuntimeException {
int[] id = new int[1];
synchronized (mStateLock) {
mState = STATE_UNINITIALIZED;
// native initialization
int result = native_setup(new WeakReference This method must be called when the Visualizer is enabled.
* @param waveform array of bytes where the waveform should be returned
* @return {@link #SUCCESS} in case of success,
* {@link #ERROR_NO_MEMORY}, {@link #ERROR_INVALID_OPERATION} or {@link #ERROR_DEAD_OBJECT}
* in case of failure.
* @throws IllegalStateException
*/
public int getWaveForm(byte[] waveform)
throws IllegalStateException {
synchronized (mStateLock) {
if (mState != STATE_ENABLED) {
throw(new IllegalStateException("getWaveForm() called in wrong state: "+mState));
}
return native_getWaveForm(waveform);
}
}
/**
* Returns a frequency capture of currently playing audio content.
* This method must be called when the Visualizer is enabled.
* The capture is an 8-bit magnitude FFT, the frequency range covered being 0 (DC) to half of
* the sampling rate returned by {@link #getSamplingRate()}. The capture returns the real and
* imaginary parts of a number of frequency points equal to half of the capture size plus one.
* Note: only the real part is returned for the first point (DC) and the last point
* (sampling frequency / 2).
* The layout in the returned byte array is as follows:
* Data in the waveform buffer is valid only within the scope of the callback.
* Applications which needs access to the waveform data after returning from the callback
* should make a copy of the data instead of holding a reference.
* @param visualizer Visualizer object on which the listener is registered.
* @param waveform array of bytes containing the waveform representation.
* @param samplingRate sampling rate of the audio visualized.
*/
void onWaveFormDataCapture(Visualizer visualizer, byte[] waveform, int samplingRate);
/**
* Method called when a new frequency capture is available.
* Data in the fft buffer is valid only within the scope of the callback.
* Applications which needs access to the fft data after returning from the callback
* should make a copy of the data instead of holding a reference.
* @param visualizer Visualizer object on which the listener is registered.
* @param fft array of bytes containing the frequency representation.
* @param samplingRate sampling rate of the audio visualized.
*/
void onFftDataCapture(Visualizer visualizer, byte[] fft, int samplingRate);
}
/**
* Registers an OnDataCaptureListener interface and specifies the rate at which the capture
* should be updated as well as the type of capture requested.
* Call this method with a null listener to stop receiving the capture updates.
* @param listener OnDataCaptureListener registered
* @param rate rate in milliHertz at which the capture should be updated
* @param waveform true if a waveform capture is requested: the onWaveFormDataCapture()
* method will be called on the OnDataCaptureListener interface.
* @param fft true if a frequency capture is requested: the onFftDataCapture() method will be
* called on the OnDataCaptureListener interface.
* @return {@link #SUCCESS} in case of success,
* {@link #ERROR_NO_INIT} or {@link #ERROR_BAD_VALUE} in case of failure.
*/
public int setDataCaptureListener(OnDataCaptureListener listener,
int rate, boolean waveform, boolean fft) {
synchronized (mListenerLock) {
mCaptureListener = listener;
}
if (listener == null) {
// make sure capture callback is stopped in native code
waveform = false;
fft = false;
}
int status = native_setPeriodicCapture(rate, waveform, fft);
if (status == SUCCESS) {
if ((listener != null) && (mNativeEventHandler == null)) {
Looper looper;
if ((looper = Looper.myLooper()) != null) {
mNativeEventHandler = new NativeEventHandler(this, looper);
} else if ((looper = Looper.getMainLooper()) != null) {
mNativeEventHandler = new NativeEventHandler(this, looper);
} else {
mNativeEventHandler = null;
status = ERROR_NO_INIT;
}
}
}
return status;
}
/**
* @hide
*
* The OnServerDiedListener interface defines a method called by the Visualizer to indicate that
* the connection to the native media server has been broken and that the Visualizer object will
* need to be released and re-created.
* The client application can implement this interface and register the listener with the
* {@link #setServerDiedListener(OnServerDiedListener)} method.
*/
public interface OnServerDiedListener {
/**
* @hide
*
* Method called when the native media server has died.
* If the native media server encounters a fatal error and needs to restart, the binder
* connection from the {@link #Visualizer} to the media server will be broken. Data capture
* callbacks will stop happening, and client initiated calls to the {@link #Visualizer}
* instance will fail with the error code {@link #DEAD_OBJECT}. To restore functionality,
* clients should {@link #release()} their old visualizer and create a new instance.
*/
void onServerDied();
}
/**
* @hide
*
* Registers an OnServerDiedListener interface.
* Call this method with a null listener to stop receiving server death notifications.
* @return {@link #SUCCESS} in case of success,
*/
public int setServerDiedListener(OnServerDiedListener listener) {
synchronized (mListenerLock) {
mServerDiedListener = listener;
}
return SUCCESS;
}
/**
* Helper class to handle the forwarding of native events to the appropriate listeners
*/
private class NativeEventHandler extends Handler
{
private Visualizer mVisualizer;
public NativeEventHandler(Visualizer v, Looper looper) {
super(looper);
mVisualizer = v;
}
private void handleCaptureMessage(Message msg) {
OnDataCaptureListener l = null;
synchronized (mListenerLock) {
l = mVisualizer.mCaptureListener;
}
if (l != null) {
byte[] data = (byte[])msg.obj;
int samplingRate = msg.arg1;
switch(msg.what) {
case NATIVE_EVENT_PCM_CAPTURE:
l.onWaveFormDataCapture(mVisualizer, data, samplingRate);
break;
case NATIVE_EVENT_FFT_CAPTURE:
l.onFftDataCapture(mVisualizer, data, samplingRate);
break;
default:
Log.e(TAG,"Unknown native event in handleCaptureMessge: "+msg.what);
break;
}
}
}
private void handleServerDiedMessage(Message msg) {
OnServerDiedListener l = null;
synchronized (mListenerLock) {
l = mVisualizer.mServerDiedListener;
}
if (l != null)
l.onServerDied();
}
@Override
public void handleMessage(Message msg) {
if (mVisualizer == null) {
return;
}
switch(msg.what) {
case NATIVE_EVENT_PCM_CAPTURE:
case NATIVE_EVENT_FFT_CAPTURE:
handleCaptureMessage(msg);
break;
case NATIVE_EVENT_SERVER_DIED:
handleServerDiedMessage(msg);
break;
default:
Log.e(TAG,"Unknown native event: "+msg.what);
break;
}
}
}
//---------------------------------------------------------
// Interface definitions
//--------------------
private static native final void native_init();
private native final int native_setup(Object audioeffect_this,
int audioSession,
int[] id);
private native final void native_finalize();
private native final void native_release();
private native final int native_setEnabled(boolean enabled);
private native final boolean native_getEnabled();
private native final int native_setCaptureSize(int size);
private native final int native_getCaptureSize();
private native final int native_setScalingMode(int mode);
private native final int native_getScalingMode();
private native final int native_setMeasurementMode(int mode);
private native final int native_getMeasurementMode();
private native final int native_getSamplingRate();
private native final int native_getWaveForm(byte[] waveform);
private native final int native_getFft(byte[] fft);
private native final int native_getPeakRms(MeasurementPeakRms measurement);
private native final int native_setPeriodicCapture(int rate, boolean waveForm, boolean fft);
//---------------------------------------------------------
// Java methods called from the native side
//--------------------
@SuppressWarnings("unused")
private static void postEventFromNative(Object effect_ref,
int what, int arg1, int arg2, Object obj) {
Visualizer visu = (Visualizer)((WeakReference)effect_ref).get();
if (visu == null) {
return;
}
if (visu.mNativeEventHandler != null) {
Message m = visu.mNativeEventHandler.obtainMessage(what, arg1, arg2, obj);
visu.mNativeEventHandler.sendMessage(m);
}
}
}
*
*
*
* @param fft array of bytes where the FFT should be returned
* @return {@link #SUCCESS} in case of success,
* {@link #ERROR_NO_MEMORY}, {@link #ERROR_INVALID_OPERATION} or {@link #ERROR_DEAD_OBJECT}
* in case of failure.
* @throws IllegalStateException
*/
public int getFft(byte[] fft)
throws IllegalStateException {
synchronized (mStateLock) {
if (mState != STATE_ENABLED) {
throw(new IllegalStateException("getFft() called in wrong state: "+mState));
}
return native_getFft(fft);
}
}
/**
* A class to store peak and RMS values.
* Peak and RMS are expressed in mB, as described in the
* {@link Visualizer#MEASUREMENT_MODE_PEAK_RMS} measurement mode.
*/
public static final class MeasurementPeakRms {
/**
* The peak value in mB.
*/
public int mPeak;
/**
* The RMS value in mB.
*/
public int mRms;
}
/**
* Retrieves the latest peak and RMS measurement.
* Sets the peak and RMS fields of the supplied {@link Visualizer.MeasurementPeakRms} to the
* latest measured values.
* @param measurement a non-null {@link Visualizer.MeasurementPeakRms} instance to store
* the measurement values.
* @return {@link #SUCCESS} in case of success, {@link #ERROR_BAD_VALUE},
* {@link #ERROR_NO_MEMORY}, {@link #ERROR_INVALID_OPERATION} or {@link #ERROR_DEAD_OBJECT}
* in case of failure.
*/
public int getMeasurementPeakRms(MeasurementPeakRms measurement) {
if (measurement == null) {
Log.e(TAG, "Cannot store measurements in a null object");
return ERROR_BAD_VALUE;
}
synchronized (mStateLock) {
if (mState != STATE_ENABLED) {
throw (new IllegalStateException("getMeasurementPeakRms() called in wrong state: "
+ mState));
}
return native_getPeakRms(measurement);
}
}
//---------------------------------------------------------
// Interface definitions
//--------------------
/**
* The OnDataCaptureListener interface defines methods called by the Visualizer to periodically
* update the audio visualization capture.
* The client application can implement this interface and register the listener with the
* {@link #setDataCaptureListener(OnDataCaptureListener, int, boolean, boolean)} method.
*/
public interface OnDataCaptureListener {
/**
* Method called when a new waveform capture is available.
* Index
* 0
* 1
* 2
* 3
* 4
* 5
* ...
* n - 2
* n - 1 Data
* Rf0
* Rf(n/2)
* Rf1
* If1
* Rf2
* If2
* ...
* Rf(n-1)/2
* If(n-1)/2