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Equalizer

public class Equalizer
extends AudioEffect

java.lang.Object
   ↳ android.media.audiofx.AudioEffect
     ↳ android.media.audiofx.Equalizer


An Equalizer is used to alter the frequency response of a particular music source or of the main output mix.

An application creates an Equalizer object to instantiate and control an Equalizer engine in the audio framework. The application can either simply use predefined presets or have a more precise control of the gain in each frequency band controlled by the equalizer.

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

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

NOTE: attaching an Equalizer 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 Equalizer.OnParameterChangeListener

The OnParameterChangeListener interface defines a method called by the Equalizer when a parameter value has changed. 

class Equalizer.Settings

The Settings class regroups all equalizer parameters. 

Constants

int PARAM_BAND_FREQ_RANGE

Band frequency range.

int PARAM_BAND_LEVEL

Band level.

int PARAM_CENTER_FREQ

Band center frequency.

int PARAM_CURRENT_PRESET

Current preset.

int PARAM_GET_BAND

Band for a given frequency.

int PARAM_GET_NUM_OF_PRESETS

Request number of presets.

int PARAM_GET_PRESET_NAME

Request preset name.

int PARAM_LEVEL_RANGE

Band level range.

int PARAM_NUM_BANDS

Number of bands.

int PARAM_STRING_SIZE_MAX

Maximum size for preset name

Inherited constants

From class android.media.audiofx.AudioEffect

Inherited fields

From class android.media.audiofx.AudioEffect

Public constructors

Equalizer(int priority, int audioSession)

Class constructor.

Public methods

short getBand(int frequency)

Gets the band that has the most effect on the given frequency.

int[] getBandFreqRange(short band)

Gets the frequency range of the given frequency band.

short getBandLevel(short band)

Gets the gain set for the given equalizer band.

short[] getBandLevelRange()

Gets the level range for use by setBandLevel(short, short).

int getCenterFreq(short band)

Gets the center frequency of the given band.

short getCurrentPreset()

Gets current preset.

short getNumberOfBands()

Gets the number of frequency bands supported by the Equalizer engine.

short getNumberOfPresets()

Gets the total number of presets the equalizer supports.

String getPresetName(short preset)

Gets the preset name based on the index.

Equalizer.Settings getProperties()

Gets the equalizer properties.

void setBandLevel(short band, short level)

Sets the given equalizer band to the given gain value.

void setParameterListener(Equalizer.OnParameterChangeListener listener)

Registers an OnParameterChangeListener interface.

void setProperties(Equalizer.Settings settings)

Sets the equalizer properties.

void usePreset(short preset)

Sets the equalizer according to the given preset.

Inherited methods

From class android.media.audiofx.AudioEffect
From class java.lang.Object

Constants

PARAM_BAND_FREQ_RANGE

Added in API level 9
int PARAM_BAND_FREQ_RANGE

Band frequency range. Parameter ID for Equalizer.OnParameterChangeListener

Constant Value: 4 (0x00000004)

PARAM_BAND_LEVEL

Added in API level 9
int PARAM_BAND_LEVEL

Band level. Parameter ID for OnParameterChangeListener

Constant Value: 2 (0x00000002)

PARAM_CENTER_FREQ

Added in API level 9
int PARAM_CENTER_FREQ

Band center frequency. Parameter ID for OnParameterChangeListener

Constant Value: 3 (0x00000003)

PARAM_CURRENT_PRESET

Added in API level 9
int PARAM_CURRENT_PRESET

Current preset. Parameter ID for OnParameterChangeListener

Constant Value: 6 (0x00000006)

PARAM_GET_BAND

Added in API level 9
int PARAM_GET_BAND

Band for a given frequency. Parameter ID for OnParameterChangeListener

Constant Value: 5 (0x00000005)

PARAM_GET_NUM_OF_PRESETS

Added in API level 9
int PARAM_GET_NUM_OF_PRESETS

Request number of presets. Parameter ID for OnParameterChangeListener

Constant Value: 7 (0x00000007)

PARAM_GET_PRESET_NAME

Added in API level 9
int PARAM_GET_PRESET_NAME

Request preset name. Parameter ID for OnParameterChangeListener

Constant Value: 8 (0x00000008)

PARAM_LEVEL_RANGE

Added in API level 9
int PARAM_LEVEL_RANGE

Band level range. Parameter ID for OnParameterChangeListener

Constant Value: 1 (0x00000001)

PARAM_NUM_BANDS

Added in API level 9
int PARAM_NUM_BANDS

Number of bands. Parameter ID for OnParameterChangeListener

Constant Value: 0 (0x00000000)

PARAM_STRING_SIZE_MAX

Added in API level 9
int PARAM_STRING_SIZE_MAX

Maximum size for preset name

Constant Value: 32 (0x00000020)

Public constructors

Equalizer

Added in API level 9
Equalizer (int priority, 
                int audioSession)

Class constructor.

Parameters
priority int: the priority level requested by the application for controlling the Equalizer 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 int: system wide unique audio session identifier. The Equalizer 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

getBand

Added in API level 9
short getBand (int frequency)

Gets the band that has the most effect on the given frequency.

Parameters
frequency int: frequency in milliHertz which is to be equalized via the returned band.
Returns
short the frequency band that has most effect on the given frequency.
Throws
IllegalStateException
IllegalArgumentException
UnsupportedOperationException
IllegalStateException
IllegalArgumentException

getBandFreqRange

Added in API level 9
int[] getBandFreqRange (short band)

Gets the frequency range of the given frequency band.

Parameters
band short: frequency band whose frequency range is requested. The numbering of the bands starts from 0 and ends at (number of bands - 1).
Returns
int[] the frequency range in millHertz in an array of integers. The first element is the lower limit of the range, the second element the upper limit.
Throws
IllegalStateException
IllegalArgumentException
UnsupportedOperationException
IllegalStateException
IllegalArgumentException

getBandLevel

Added in API level 9
short getBandLevel (short band)

Gets the gain set for the given equalizer band.

Parameters
band short: frequency band whose gain is requested. The numbering of the bands starts from 0 and ends at (number of bands - 1).
Returns
short the gain in millibels of the given band.
Throws
IllegalStateException
IllegalArgumentException
UnsupportedOperationException
IllegalStateException
IllegalArgumentException

getBandLevelRange

Added in API level 9
short[] getBandLevelRange ()

Gets the level range for use by setBandLevel(short, short). The level is expressed in milliBel.

Returns
short[] the band level range in an array of short integers. The first element is the lower limit of the range, the second element the upper limit.
Throws
IllegalStateException
IllegalArgumentException
UnsupportedOperationException
IllegalStateException
IllegalArgumentException

getCenterFreq

Added in API level 9
int getCenterFreq (short band)

Gets the center frequency of the given band.

Parameters
band short: frequency band whose center frequency is requested. The numbering of the bands starts from 0 and ends at (number of bands - 1).
Returns
int the center frequency in milliHertz
Throws
IllegalStateException
IllegalArgumentException
UnsupportedOperationException
IllegalStateException
IllegalArgumentException

getCurrentPreset

Added in API level 9
short getCurrentPreset ()

Gets current preset.

Returns
short the preset that is set at the moment.
Throws
IllegalStateException
IllegalArgumentException
UnsupportedOperationException
IllegalStateException
IllegalArgumentException

getNumberOfBands

Added in API level 9
short getNumberOfBands ()

Gets the number of frequency bands supported by the Equalizer engine.

Returns
short the number of bands
Throws
IllegalStateException
IllegalArgumentException
UnsupportedOperationException
IllegalStateException
IllegalArgumentException

getNumberOfPresets

Added in API level 9
short getNumberOfPresets ()

Gets the total number of presets the equalizer supports. The presets will have indices [0, number of presets-1].

Returns
short the number of presets the equalizer supports.
Throws
IllegalStateException
IllegalArgumentException
UnsupportedOperationException
IllegalStateException
IllegalArgumentException

getPresetName

Added in API level 9
String getPresetName (short preset)

Gets the preset name based on the index.

Parameters
preset short: index of the preset. The valid range is [0, number of presets-1].
Returns
String a string containing the name of the given preset.
Throws
IllegalStateException
IllegalArgumentException
UnsupportedOperationException

getProperties

Added in API level 9
Equalizer.Settings getProperties ()

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

Returns
Equalizer.Settings an Equalizer.Settings object containing all current parameters values
Throws
IllegalStateException
IllegalArgumentException
UnsupportedOperationException
IllegalStateException
IllegalArgumentException

setBandLevel

Added in API level 9
void setBandLevel (short band, 
                short level)

Sets the given equalizer band to the given gain value.

Parameters
band short: frequency band that will have the new gain. The numbering of the bands starts from 0 and ends at (number of bands - 1).
level short: new gain in millibels that will be set to the given band. getBandLevelRange() will define the maximum and minimum values.
Throws
IllegalStateException
IllegalArgumentException
UnsupportedOperationException
IllegalStateException
IllegalArgumentException
UnsupportedOperationException

See also:

setParameterListener

Added in API level 9
void setParameterListener (Equalizer.OnParameterChangeListener listener)

Registers an OnParameterChangeListener interface.

Parameters
listener Equalizer.OnParameterChangeListener: OnParameterChangeListener interface registered

setProperties

Added in API level 9
void setProperties (Equalizer.Settings settings)

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

Parameters
settings Equalizer.Settings: an Equalizer.Settings object containing the properties to apply
Throws
IllegalStateException
IllegalArgumentException
UnsupportedOperationException
IllegalStateException
IllegalArgumentException

usePreset

Added in API level 9
void usePreset (short preset)

Sets the equalizer according to the given preset.

Parameters
preset short: new preset that will be taken into use. The valid range is [0, number of presets-1].
Throws
IllegalStateException
IllegalArgumentException
UnsupportedOperationException
IllegalStateException
IllegalArgumentException
UnsupportedOperationException

See also:

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