Android APIs
public class

Virtualizer

extends AudioEffect
java.lang.Object
   ↳ android.media.audiofx.AudioEffect
     ↳ android.media.audiofx.Virtualizer

Class Overview

An audio virtualizer is a general name for an effect to spatialize audio channels. The exact behavior of this effect is dependent on the number of audio input channels and the types and number of audio output channels of the device. For example, in the case of a stereo input and stereo headphone output, a stereo widening effect is used when this effect is turned on.

An application creates a Virtualizer object to instantiate and control a virtualizer engine in the audio framework.

The methods, parameter types and units exposed by the Virtualizer implementation are directly mapping those defined by the OpenSL ES 1.0.1 Specification (http://www.khronos.org/opensles/) for the SLVirtualizerItf interface. Please refer to this specification for more details.

To attach the Virtualizer to a particular AudioTrack or MediaPlayer, specify the audio session ID of this AudioTrack or MediaPlayer when constructing the Virtualizer.

NOTE: attaching a Virtualizer to the global audio output mix by use of session 0 is deprecated.

See getAudioSessionId() for details on audio sessions.

See AudioEffect class for more details on controlling audio effects.

Summary

Nested Classes
interface Virtualizer.OnParameterChangeListener The OnParameterChangeListener interface defines a method called by the Virtualizer when a parameter value has changed. 
class Virtualizer.Settings The Settings class regroups all virtualizer parameters. 
Constants
int PARAM_STRENGTH Virtualizer effect strength.
int PARAM_STRENGTH_SUPPORTED Is strength parameter supported by virtualizer engine.
int VIRTUALIZATION_MODE_AUTO A virtualization mode used to indicate the virtualizer effect must stop forcing the processing to a particular mode in forceVirtualizationMode(int).
int VIRTUALIZATION_MODE_BINAURAL A virtualization mode typically used over headphones.
int VIRTUALIZATION_MODE_OFF A virtualization mode indicating virtualization processing is not active.
int VIRTUALIZATION_MODE_TRANSAURAL A virtualization mode typically used over speakers.
[Expand]
Inherited Constants
From class android.media.audiofx.AudioEffect
[Expand]
Inherited Fields
From class android.media.audiofx.AudioEffect
Public Constructors
Virtualizer(int priority, int audioSession)
Class constructor.
Public Methods
boolean canVirtualize(int inputChannelMask, int virtualizationMode)
Checks if the combination of a channel mask and virtualization mode is supported by this virtualizer.
boolean forceVirtualizationMode(int virtualizationMode)
Forces the virtualizer effect to use the given processing mode.
Virtualizer.Settings getProperties()
Gets the virtualizer properties.
short getRoundedStrength()
Gets the current strength of the effect.
boolean getSpeakerAngles(int inputChannelMask, int virtualizationMode, int[] angles)
Queries the virtual speaker angles (azimuth and elevation) for a combination of a channel mask and virtualization mode.
boolean getStrengthSupported()
Indicates whether setting strength is supported.
int getVirtualizationMode()
Return the virtualization mode being used, if any.
void setParameterListener(Virtualizer.OnParameterChangeListener listener)
Registers an OnParameterChangeListener interface.
void setProperties(Virtualizer.Settings settings)
Sets the virtualizer properties.
void setStrength(short strength)
Sets the strength of the virtualizer effect.
[Expand]
Inherited Methods
From class android.media.audiofx.AudioEffect
From class java.lang.Object

Constants

public static final int PARAM_STRENGTH

Added in API level 9

Virtualizer effect strength. Parameter ID for Virtualizer.OnParameterChangeListener

Constant Value: 1 (0x00000001)

public static final int PARAM_STRENGTH_SUPPORTED

Added in API level 9

Is strength parameter supported by virtualizer engine. Parameter ID for getParameter().

Constant Value: 0 (0x00000000)

public static final int VIRTUALIZATION_MODE_AUTO

Added in API level 21

A virtualization mode used to indicate the virtualizer effect must stop forcing the processing to a particular mode in forceVirtualizationMode(int).

Constant Value: 1 (0x00000001)

public static final int VIRTUALIZATION_MODE_BINAURAL

Added in API level 21

A virtualization mode typically used over headphones. Binaural virtualization describes an audio processing configuration for virtualization where the left and right channels are respectively reaching the left and right ear of the user, without also feeding the opposite ear (as is the case when listening over speakers).

Such a mode is therefore meant to be used when audio is playing over stereo wired headphones or headsets, but also stereo headphones through a wireless A2DP Bluetooth link.

See canVirtualize(int, int) to verify this mode is supported by this Virtualizer.

Constant Value: 2 (0x00000002)

public static final int VIRTUALIZATION_MODE_OFF

Added in API level 21

A virtualization mode indicating virtualization processing is not active. See getVirtualizationMode() as one of the possible return value.

Constant Value: 0 (0x00000000)

public static final int VIRTUALIZATION_MODE_TRANSAURAL

Added in API level 21

A virtualization mode typically used over speakers. Transaural virtualization describes an audio processing configuration that differs from binaural (as described in VIRTUALIZATION_MODE_BINAURAL in that cross-talk is present, i.e. audio played from the left channel also reaches the right ear of the user, and vice-versa.

When supported, such a mode is therefore meant to be used when audio is playing over the built-in stereo speakers of a device, if they are featured.

See canVirtualize(int, int) to verify this mode is supported by this Virtualizer.

Constant Value: 3 (0x00000003)

Public Constructors

public Virtualizer (int priority, int audioSession)

Added in API level 9

Class constructor.

Parameters
priority the priority level requested by the application for controlling the Virtualizer engine. As the same engine can be shared by several applications, this parameter indicates how much the requesting application needs control of effect parameters. The normal priority is 0, above normal is a positive number, below normal a negative number.
audioSession system wide unique audio session identifier. The Virtualizer will be attached to the MediaPlayer or AudioTrack in the same audio session.
Throws
java.lang.IllegalStateException
java.lang.IllegalArgumentException
java.lang.UnsupportedOperationException
RuntimeException
IllegalStateException
IllegalArgumentException
UnsupportedOperationException

Public Methods

public boolean canVirtualize (int inputChannelMask, int virtualizationMode)

Added in API level 21

Checks if the combination of a channel mask and virtualization mode is supported by this virtualizer. Some virtualizer implementations may only support binaural processing (i.e. only support headphone output, see VIRTUALIZATION_MODE_BINAURAL), some may support transaural processing (i.e. for speaker output, see VIRTUALIZATION_MODE_TRANSAURAL) for the built-in speakers. Use this method to query the virtualizer implementation capabilities.

Parameters
inputChannelMask the channel mask of the content to virtualize.
virtualizationMode the mode for which virtualization processing is to be performed, one of VIRTUALIZATION_MODE_BINAURAL, VIRTUALIZATION_MODE_TRANSAURAL.
Returns
  • true if the combination of channel mask and virtualization mode is supported, false otherwise.
    An indication that a certain channel mask is not supported doesn't necessarily mean you cannot play content with that channel mask, it more likely implies the content will be downmixed before being virtualized. For instance a virtualizer that only supports a mask such as CHANNEL_OUT_STEREO will still be able to process content with a mask of CHANNEL_OUT_5POINT1, but will downmix the content to stereo first, and then will virtualize, as opposed to virtualizing each channel individually.
Throws
IllegalStateException
IllegalArgumentException
UnsupportedOperationException
IllegalStateException
IllegalArgumentException

public boolean forceVirtualizationMode (int virtualizationMode)

Added in API level 21

Forces the virtualizer effect to use the given processing mode. The effect must be enabled for the forced mode to be applied.

Parameters
virtualizationMode one of VIRTUALIZATION_MODE_BINAURAL, VIRTUALIZATION_MODE_TRANSAURAL to force a particular processing mode, or .VIRTUALIZATION_MODE_AUTO to stop forcing a mode.
Returns
  • true if the processing mode is supported, and it is successfully set, or forcing was successfully disabled, false otherwise.
Throws
IllegalStateException
IllegalArgumentException
UnsupportedOperationException
IllegalStateException
IllegalArgumentException

public Virtualizer.Settings getProperties ()

Added in API level 9

Gets the virtualizer properties. This method is useful when a snapshot of current virtualizer settings must be saved by the application.

Returns
  • a Virtualizer.Settings object containing all current parameters values
Throws
IllegalStateException
IllegalArgumentException
UnsupportedOperationException
IllegalStateException
IllegalArgumentException

public short getRoundedStrength ()

Added in API level 9

Gets the current strength of the effect.

Returns
  • the strength of the effect. The valid range for strength is [0, 1000], where 0 per mille designates the mildest effect and 1000 per mille the strongest
Throws
IllegalStateException
IllegalArgumentException
UnsupportedOperationException
IllegalStateException
IllegalArgumentException

public boolean getSpeakerAngles (int inputChannelMask, int virtualizationMode, int[] angles)

Added in API level 21

Queries the virtual speaker angles (azimuth and elevation) for a combination of a channel mask and virtualization mode. If the virtualization configuration (mask and mode) is supported (see canVirtualize(int, int), the array angles will contain upon return the definition of each virtual speaker and its azimuth and elevation angles relative to the listener.
Note that in some virtualizer implementations, the angles may be strength-dependent.

Parameters
inputChannelMask the channel mask of the content to virtualize.
virtualizationMode the mode for which virtualization processing is to be performed, one of VIRTUALIZATION_MODE_BINAURAL, VIRTUALIZATION_MODE_TRANSAURAL.
angles a non-null array whose length is 3 times the number of channels in the channel mask. If the method indicates the configuration is supported, the array will contain upon return triplets of values: for each channel i among the channels of the mask:
  • the element at index 3*i in the array contains the speaker identification (e.g. CHANNEL_OUT_FRONT_LEFT),
  • the element at index 3*i+1 contains its corresponding azimuth angle expressed in degrees, where 0 is the direction the listener faces, 180 is behind the listener, and -90 is to her/his left,
  • the element at index 3*i+2 contains its corresponding elevation angle where +90 is directly above the listener, 0 is the horizontal plane, and -90 is directly below the listener.
Returns
  • true if the combination of channel mask and virtualization mode is supported, false otherwise.
Throws
IllegalStateException
IllegalArgumentException
UnsupportedOperationException
IllegalStateException
IllegalArgumentException

public boolean getStrengthSupported ()

Added in API level 9

Indicates whether setting strength is supported. If this method returns false, only one strength is supported and the setStrength() method always rounds to that value.

Returns
  • true is strength parameter is supported, false otherwise

public int getVirtualizationMode ()

Added in API level 21

Return the virtualization mode being used, if any.

Returns
Throws
IllegalStateException
UnsupportedOperationException
IllegalStateException

public void setParameterListener (Virtualizer.OnParameterChangeListener listener)

Added in API level 9

Registers an OnParameterChangeListener interface.

Parameters
listener OnParameterChangeListener interface registered

public void setProperties (Virtualizer.Settings settings)

Added in API level 9

Sets the virtualizer properties. This method is useful when virtualizer settings have to be applied from a previous backup.

Parameters
settings a Virtualizer.Settings object containing the properties to apply
Throws
IllegalStateException
IllegalArgumentException
UnsupportedOperationException
IllegalStateException
IllegalArgumentException

public void setStrength (short strength)

Added in API level 9

Sets the strength of the virtualizer effect. If the implementation does not support per mille accuracy for setting the strength, it is allowed to round the given strength to the nearest supported value. You can use the getRoundedStrength() method to query the (possibly rounded) value that was actually set.

Parameters
strength strength of the effect. The valid range for strength strength is [0, 1000], where 0 per mille designates the mildest effect and 1000 per mille designates the strongest.
Throws
IllegalStateException
IllegalArgumentException
UnsupportedOperationException
IllegalStateException
IllegalArgumentException
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