Added in API level 1

SoundPool

open class SoundPool
kotlin.Any
   ↳ android.media.SoundPool

The SoundPool class manages and plays audio resources for applications.

A SoundPool is a collection of sound samples that can be loaded into memory from a resource inside the APK or from a file in the file system. The SoundPool library uses the MediaCodec service to decode the audio into raw 16-bit PCM. This allows applications to ship with compressed streams without having to suffer the CPU load and latency of decompressing during playback.

Soundpool sounds are expected to be short as they are predecoded into memory. Each decoded sound is internally limited to one megabyte storage, which represents approximately 5.6 seconds at 44.1kHz stereo (the duration is proportionally longer at lower sample rates or a channel mask of mono). A decoded audio sound will be truncated if it would exceed the per-sound one megabyte storage space.

In addition to low-latency playback, SoundPool can also manage the number of audio streams being rendered at once. When the SoundPool object is constructed, the maxStreams parameter sets the maximum number of streams that can be played at a time from this single SoundPool. SoundPool tracks the number of active streams. If the maximum number of streams is exceeded, SoundPool will automatically stop a previously playing stream based first on priority and then by age within that priority. Limiting the maximum number of streams helps to cap CPU loading and reducing the likelihood that audio mixing will impact visuals or UI performance.

Sounds can be looped by setting a non-zero loop value. A value of -1 causes the sound to loop forever. In this case, the application must explicitly call the stop() function to stop the sound. Any other non-zero value will cause the sound to repeat the specified number of times, e.g. a value of 3 causes the sound to play a total of 4 times.

The playback rate can also be changed. A playback rate of 1.0 causes the sound to play at its original frequency (resampled, if necessary, to the hardware output frequency). A playback rate of 2.0 causes the sound to play at twice its original frequency, and a playback rate of 0.5 causes it to play at half its original frequency. The playback rate range is 0.5 to 2.0.

Priority runs low to high, i.e. higher numbers are higher priority. Priority is used when a call to play() would cause the number of active streams to exceed the value established by the maxStreams parameter when the SoundPool was created. In this case, the stream allocator will stop the lowest priority stream. If there are multiple streams with the same low priority, it will choose the oldest stream to stop. In the case where the priority of the new stream is lower than all the active streams, the new sound will not play and the play() function will return a streamID of zero.

Let's examine a typical use case: A game consists of several levels of play. For each level, there is a set of unique sounds that are used only by that level. In this case, the game logic should create a new SoundPool object when the first level is loaded. The level data itself might contain the list of sounds to be used by this level. The loading logic iterates through the list of sounds calling the appropriate SoundPool.load() function. This should typically be done early in the process to allow time for decompressing the audio to raw PCM format before they are needed for playback.

Once the sounds are loaded and play has started, the application can trigger sounds by calling SoundPool.play(). Playing streams can be paused or resumed, and the application can also alter the pitch by adjusting the playback rate in real-time for doppler or synthesis effects.

Note that since streams can be stopped due to resource constraints, the streamID is a reference to a particular instance of a stream. If the stream is stopped to allow a higher priority stream to play, the stream is no longer valid. However, the application is allowed to call methods on the streamID without error. This may help simplify program logic since the application need not concern itself with the stream lifecycle.

In our example, when the player has completed the level, the game logic should call SoundPool.release() to release all the native resources in use and then set the SoundPool reference to null. If the player starts another level, a new SoundPool is created, sounds are loaded, and play resumes.

Summary

Nested classes
open

Builder class for SoundPool objects.
abstract

Public constructors
SoundPool(maxStreams: Int, streamType: Int, srcQuality: Int)

Constructor.
Public methods
Unit

Pause all active streams.
Unit

Resume all previously active streams.
open Int
load(path: String!, priority: Int)

Load the sound from the specified path.
open Int
load(context: Context!, resId: Int, priority: Int)

Load the sound from the specified APK resource.
open Int
load(afd: AssetFileDescriptor!, priority: Int)

Load the sound from an asset file descriptor.
open Int
load(fd: FileDescriptor!, offset: Long, length: Long, priority: Int)

Load the sound from a FileDescriptor.
Unit
pause(streamID: Int)

Pause a playback stream.
Int
play(soundID: Int, leftVolume: Float, rightVolume: Float, priority: Int, loop: Int, rate: Float)

Play a sound from a sound ID.
Unit

Release the SoundPool resources.
Unit
resume(streamID: Int)

Resume a playback stream.
Unit
setLoop(streamID: Int, loop: Int)

Set loop mode.
open Unit

Sets the callback hook for the OnLoadCompleteListener.
Unit
setPriority(streamID: Int, priority: Int)

Change stream priority.
Unit
setRate(streamID: Int, rate: Float)

Change playback rate.
Unit
setVolume(streamID: Int, leftVolume: Float, rightVolume: Float)

Set stream volume.
Unit
stop(streamID: Int)

Stop a playback stream.
Boolean
unload(soundID: Int)

Unload a sound from a sound ID.
Protected methods
open Unit

Public constructors

SoundPool

Added in API level 1
SoundPool(
    maxStreams: Int, 
    streamType: Int, 
    srcQuality: Int)

Deprecated: use SoundPool.Builder instead to create and configure a SoundPool instance

Constructor. Constructs a SoundPool object with the following characteristics:

Parameters
maxStreams Int: the maximum number of simultaneous streams for this SoundPool object
streamType Int: the audio stream type as described in AudioManager For example, game applications will normally use AudioManager#STREAM_MUSIC.
srcQuality Int: the sample-rate converter quality. Currently has no effect. Use 0 for the default.
Return
a SoundPool object, or null if creation failed

Public methods

autoPause

Added in API level 8
fun autoPause(): Unit

Pause all active streams. Pause all streams that are currently playing. This function iterates through all the active streams and pauses any that are playing. It also sets a flag so that any streams that are playing can be resumed by calling autoResume().

autoResume

Added in API level 8
fun autoResume(): Unit

Resume all previously active streams. Automatically resumes all streams that were paused in previous calls to autoPause().

load

Added in API level 1
open fun load(
    path: String!, 
    priority: Int
): Int

Load the sound from the specified path.

Parameters
path String!: the path to the audio file
priority Int: the priority of the sound. Currently has no effect. Use a value of 1 for future compatibility.
Return
Int a sound ID. This value can be used to play or unload the sound.

load

Added in API level 1
open fun load(
    context: Context!, 
    resId: Int, 
    priority: Int
): Int

Load the sound from the specified APK resource. Note that the extension is dropped. For example, if you want to load a sound from the raw resource file "explosion.mp3", you would specify "R.raw.explosion" as the resource ID. Note that this means you cannot have both an "explosion.wav" and an "explosion.mp3" in the res/raw directory.

Parameters
context Context!: the application context
resId Int: the resource ID
priority Int: the priority of the sound. Currently has no effect. Use a value of 1 for future compatibility.
Return
Int a sound ID. This value can be used to play or unload the sound.

load

Added in API level 3
open fun load(
    afd: AssetFileDescriptor!, 
    priority: Int
): Int

Load the sound from an asset file descriptor.

Parameters
afd AssetFileDescriptor!: an asset file descriptor
priority Int: the priority of the sound. Currently has no effect. Use a value of 1 for future compatibility.
Return
Int a sound ID. This value can be used to play or unload the sound.

load

Added in API level 3
open fun load(
    fd: FileDescriptor!, 
    offset: Long, 
    length: Long, 
    priority: Int
): Int

Load the sound from a FileDescriptor. This version is useful if you store multiple sounds in a single binary. The offset specifies the offset from the start of the file and the length specifies the length of the sound within the file.

Parameters
fd FileDescriptor!: a FileDescriptor object
offset Long: offset to the start of the sound
length Long: length of the sound
priority Int: the priority of the sound. Currently has no effect. Use a value of 1 for future compatibility.
Return
Int a sound ID. This value can be used to play or unload the sound.

pause

Added in API level 1
fun pause(streamID: Int): Unit

Pause a playback stream. Pause the stream specified by the streamID. This is the value returned by the play() function. If the stream is playing, it will be paused. If the stream is not playing (e.g. is stopped or was previously paused), calling this function will have no effect.

Parameters
streamID Int: a streamID returned by the play() function

play

Added in API level 1
fun play(
    soundID: Int, 
    leftVolume: Float, 
    rightVolume: Float, 
    priority: Int, 
    loop: Int, 
    rate: Float
): Int

Play a sound from a sound ID. Play the sound specified by the soundID. This is the value returned by the load() function. Returns a non-zero streamID if successful, zero if it fails. The streamID can be used to further control playback. Note that calling play() may cause another sound to stop playing if the maximum number of active streams is exceeded. A loop value of -1 means loop forever, a value of 0 means don't loop, other values indicate the number of repeats, e.g. a value of 1 plays the audio twice. The playback rate allows the application to vary the playback rate (pitch) of the sound. A value of 1.0 means play back at the original frequency. A value of 2.0 means play back twice as fast, and a value of 0.5 means playback at half speed.

Parameters
soundID Int: a soundID returned by the load() function
leftVolume Float: left volume value (range = 0.0 to 1.0)
rightVolume Float: right volume value (range = 0.0 to 1.0)
priority Int: stream priority (0 = lowest priority)
loop Int: loop mode (0 = no loop, -1 = loop forever)
rate Float: playback rate (1.0 = normal playback, range 0.5 to 2.0)
Return
Int non-zero streamID if successful, zero if failed

release

Added in API level 1
fun release(): Unit

Release the SoundPool resources. Release all memory and native resources used by the SoundPool object. The SoundPool can no longer be used and the reference should be set to null.

resume

Added in API level 1
fun resume(streamID: Int): Unit

Resume a playback stream. Resume the stream specified by the streamID. This is the value returned by the play() function. If the stream is paused, this will resume playback. If the stream was not previously paused, calling this function will have no effect.

Parameters
streamID Int: a streamID returned by the play() function

setLoop

Added in API level 1
fun setLoop(
    streamID: Int, 
    loop: Int
): Unit

Set loop mode. Change the loop mode. A loop value of -1 means loop forever, a value of 0 means don't loop, other values indicate the number of repeats, e.g. a value of 1 plays the audio twice. If the stream does not exist, it will have no effect.

Parameters
streamID Int: a streamID returned by the play() function
loop Int: loop mode (0 = no loop, -1 = loop forever)

setOnLoadCompleteListener

Added in API level 8
open fun setOnLoadCompleteListener(listener: SoundPool.OnLoadCompleteListener!): Unit

Sets the callback hook for the OnLoadCompleteListener.

setPriority

Added in API level 1
fun setPriority(
    streamID: Int, 
    priority: Int
): Unit

Change stream priority. Change the priority of the stream specified by the streamID. This is the value returned by the play() function. Affects the order in which streams are re-used to play new sounds. If the stream does not exist, it will have no effect.

Parameters
streamID Int: a streamID returned by the play() function

setRate

Added in API level 1
fun setRate(
    streamID: Int, 
    rate: Float
): Unit

Change playback rate. The playback rate allows the application to vary the playback rate (pitch) of the sound. A value of 1.0 means playback at the original frequency. A value of 2.0 means playback twice as fast, and a value of 0.5 means playback at half speed. If the stream does not exist, it will have no effect.

Parameters
streamID Int: a streamID returned by the play() function
rate Float: playback rate (1.0 = normal playback, range 0.5 to 2.0)

setVolume

Added in API level 1
fun setVolume(
    streamID: Int, 
    leftVolume: Float, 
    rightVolume: Float
): Unit

Set stream volume. Sets the volume on the stream specified by the streamID. This is the value returned by the play() function. The value must be in the range of 0.0 to 1.0. If the stream does not exist, it will have no effect.

Parameters
streamID Int: a streamID returned by the play() function
leftVolume Float: left volume value (range = 0.0 to 1.0)
rightVolume Float: right volume value (range = 0.0 to 1.0)

stop

Added in API level 1
fun stop(streamID: Int): Unit

Stop a playback stream. Stop the stream specified by the streamID. This is the value returned by the play() function. If the stream is playing, it will be stopped. It also releases any native resources associated with this stream. If the stream is not playing, it will have no effect.

Parameters
streamID Int: a streamID returned by the play() function

unload

Added in API level 1
fun unload(soundID: Int): Boolean

Unload a sound from a sound ID. Unloads the sound specified by the soundID. This is the value returned by the load() function. Returns true if the sound is successfully unloaded, false if the sound was already unloaded.

Parameters
soundID Int: a soundID returned by the load() function
Return
Boolean true if just unloaded, false if previously unloaded

Protected methods

finalize

Added in API level 1
protected open fun finalize(): Unit
Exceptions
java.lang.Throwable the Exception raised by this method