Visualizer

ALREADY_EXISTS

static val ALREADY_EXISTS: Int

Internal operation status. Not returned by any method.

Value: -2

ERROR

static val ERROR: Int

Unspecified error.

Value: -1

ERROR_BAD_VALUE

static val ERROR_BAD_VALUE: Int

Operation failed due to bad parameter value.

Value: -4

ERROR_DEAD_OBJECT

static val ERROR_DEAD_OBJECT: Int

Operation failed due to dead remote object.

Value: -7

ERROR_INVALID_OPERATION

static val ERROR_INVALID_OPERATION: Int

Operation failed because it was requested in wrong state.

Value: -5

ERROR_NO_INIT

static val ERROR_NO_INIT: Int

Operation failed due to bad object initialization.

Value: -3

ERROR_NO_MEMORY

static val ERROR_NO_MEMORY: Int

Operation failed due to lack of memory.

Value: -6

MEASUREMENT_MODE_NONE

static val MEASUREMENT_MODE_NONE: Int

Defines a measurement mode in which no measurements are performed.

Value: 0

MEASUREMENT_MODE_PEAK_RMS

static val MEASUREMENT_MODE_PEAK_RMS: Int

Defines a measurement mode which computes the peak and RMS value in mB below the "full scale", where 0mB is normally the maximum sample value (but see the note below). Minimum value depends on the resolution of audio samples used by the audio framework. The value of -9600mB is the minimum value for 16-bit audio systems and -14400mB or below for "high resolution" systems. Values for peak and RMS can be retrieved with getMeasurementPeakRms(android.media.audiofx.Visualizer.MeasurementPeakRms).

Note: when Visualizer effect is attached to the global session (with session ID 0), it is possible to observe RMS peaks higher than 0 dBFS, for example in the case when there are multiple audio sources playing simultaneously. In this case getMeasurementPeakRms(android.media.audiofx.Visualizer.MeasurementPeakRms) method can return a positive value.

Value: 1

SCALING_MODE_AS_PLAYED

static val SCALING_MODE_AS_PLAYED: Int

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.

Value: 1

SCALING_MODE_NORMALIZED

static val SCALING_MODE_NORMALIZED: Int

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.

Value: 0

STATE_ENABLED

static val STATE_ENABLED: Int

State of a Visualizer object that is active.

Value: 2

STATE_INITIALIZED

static val STATE_INITIALIZED: Int

State of a Visualizer object that is ready to be used.

Value: 1

STATE_UNINITIALIZED

static val STATE_UNINITIALIZED: Int

State of a Visualizer object that was not successfully initialized upon creation

Value: 0

SUCCESS

static val SUCCESS: Int

Successful operation.

Value: 0

Visualizer

Visualizer(audioSession: Int)

Class constructor.

getCaptureSize

open fun getCaptureSize(): Int

Returns current capture size.

getCaptureSizeRange

open static fun getCaptureSizeRange(): IntArray!

Returns the capture size range.

getEnabled

open fun getEnabled(): Boolean

Get current activation state of the visualizer.

getFft

open fun getFft(fft: ByteArray!): Int

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 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:

• n is the capture size returned by getCaptureSize()
• Rfk, Ifk are respectively the real and imaginary parts of the kth frequency component
• If Fs is the sampling frequency retuned by getSamplingRate() the kth frequency is: k * Fs / n

In order to obtain magnitude and phase values the following code can be used:

int n = fft.size();
        float[] magnitudes = new float[n / 2 + 1];
        float[] phases = new float[n / 2 + 1];
        magnitudes[0] = (float)Math.abs(fft[0]);      // DC
        magnitudes[n / 2] = (float)Math.abs(fft[1]);  // Nyquist
        phases[0] = phases[n / 2] = 0;
        for (int k = 1; k < n / 2; k++) {
            int i = k * 2;
            magnitudes[k] = (float)Math.hypot(fft[i], fft[i + 1]);
            phases[k] = (float)Math.atan2(fft[i + 1], fft[i]);
        }

getMaxCaptureRate

open static fun getMaxCaptureRate(): Int

Returns the maximum capture rate for the callback capture method. This is the maximum value for the rate parameter of the setDataCaptureListener(android.media.audiofx.Visualizer.OnDataCaptureListener,int,boolean,boolean) method.

getMeasurementMode

open fun getMeasurementMode(): Int

Returns the current measurement modes performed by this audio effect

getMeasurementPeakRms

open fun getMeasurementPeakRms(measurement: Visualizer.MeasurementPeakRms!): Int

Retrieves the latest peak and RMS measurement. Sets the peak and RMS fields of the supplied Visualizer.MeasurementPeakRms to the latest measured values.

getSamplingRate

open fun getSamplingRate(): Int

Returns the sampling rate of the captured audio.

getScalingMode

open fun getScalingMode(): Int

Returns the current scaling mode on the captured visualization data.

getWaveForm

open fun getWaveForm(waveform: ByteArray!): Int

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().

This method must be called when the Visualizer is enabled.

release

open fun release(): Unit

Releases the native Visualizer resources. It is a good practice to release the visualization engine when not in use.

setCaptureSize

open fun setCaptureSize(size: Int): Int

Sets the capture size, i.e. the number of bytes returned by getWaveForm(byte[]) and getFft(byte[]) methods. The capture size must be a power of 2 in the range returned by getCaptureSizeRange(). This method must not be called when the Visualizer is enabled.

setDataCaptureListener

open fun setDataCaptureListener(
    listener: Visualizer.OnDataCaptureListener?, 
    rate: Int, 
    waveform: Boolean, 
    fft: Boolean
): Int

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.

setEnabled

open fun setEnabled(enabled: Boolean): Int

Enable or disable the visualization engine.

setMeasurementMode

open fun setMeasurementMode(mode: Int): Int

Sets the combination of measurement modes to be performed by this audio effect.

setScalingMode

open fun setScalingMode(mode: Int): Int

Set the type of scaling applied on the captured visualization data.

finalize

protected open fun finalize(): Unit