A SoundPool is a collection of 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 MediaPlayer service to decode the audio + * into a raw 16-bit PCM mono or stereo stream. This allows applications + * to ship with compressed streams without having to suffer the CPU load + * and latency of decompressing during playback.
+ * + *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.
+ * + *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.
+ * + *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.
*/ public class SoundPool { @@ -37,10 +86,30 @@ public class SoundPool private int mNativeContext; // accessed by native methods + /** + * Constructor. Constructs a SoundPool object with the following + * characteristics: + * + * @param maxStreams the maximum number of simultaneous streams for this + * SoundPool object + * @param streamType the audio stream type as described in AudioManager + * For example, game applications will normally use + * {@link AudioManager#STREAM_MUSIC}. + * @param srcQuality the sample-rate converter quality. Currently has no + * effect. Use 0 for the default. + * @return a SoundPool object, or null if creation failed + */ public SoundPool(int maxStreams, int streamType, int srcQuality) { native_setup(new WeakReferenceNote 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.
+ * + * @param context the application context + * @param resId the resource ID + * @param priority the priority of the sound. Currently has no effect. + * @return a sound ID. This value can be used to play or unload the sound. + */ public int load(Context context, int resId, int priority) { AssetFileDescriptor afd = context.getResources().openRawResourceFd(resId); int id = 0; @@ -78,6 +161,13 @@ public class SoundPool return id; } + /** + * Load the sound from an asset file descriptor + * + * @param afd an asset file descriptor + * @param priority the priority of the sound. Currently has no effect. + * @return a sound ID. This value can be used to play or unload the sound. + */ public int load(AssetFileDescriptor afd, int priority) { if (afd != null) { long len = afd.getLength(); @@ -90,6 +180,19 @@ public class SoundPool } } + /** + * 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.
+ * + * @param fd a FileDescriptor object + * @param offset offset to the start of the sound + * @param length length of the sound + * @param priority the priority of the sound. Currently has no effect. + * @return a sound ID. This value can be used to play or unload the sound. + */ public int load(FileDescriptor fd, long offset, long length, int priority) { return _load(fd, offset, length, priority); } @@ -98,22 +201,107 @@ public class SoundPool private native final int _load(FileDescriptor fd, long offset, long length, int priority); + /** + * 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.
+ * + * @param soundID a soundID returned by the load() function + * @return true if just unloaded, false if previously unloaded + */ public native final boolean unload(int soundID); + /** + * 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.
+ * + * @param soundID a soundID returned by the load() function + * @return non-zero streamID if successful, zero if failed + */ public native final int play(int soundID, float leftVolume, float rightVolume, int priority, int loop, float rate); + /** + * 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.
+ * + * @param streamID a streamID returned by the play() function + */ public native final void pause(int streamID); + /** + * 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.
+ * + * @param streamID a streamID returned by the play() function + */ public native final void resume(int streamID); + /** + * 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.
+ * + * @param streamID a streamID returned by the play() function + */ public native final void stop(int streamID); + /** + * 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.
+ * + * @param streamID a streamID returned by the play() function + * @param leftVolume left volume value (range = 0.0 to 1.0) + * @param rightVolume right volume value (range = 0.0 to 1.0) + */ public native final void setVolume(int streamID, float leftVolume, float rightVolume); + /** + * 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. + * + * @param streamID a streamID returned by the play() function + */ public native final void setPriority(int streamID, int priority); + /** + * 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. + * + * @param streamID a streamID returned by the play() function + */ public native final void setLoop(int streamID, int loop); public native final void setRate(int streamID, float rate);