android/media/SoundPool.java

/*
 * Copyright (C) 2007 The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package android.media;

import android.util.AndroidRuntimeException;
import android.util.Log;
import java.io.File;
import java.io.FileDescriptor;
import android.os.ParcelFileDescriptor;
import java.lang.ref.WeakReference;
import android.content.Context;
import android.content.res.AssetFileDescriptor;
import java.io.IOException;

/**
 * The SoundPool class manages and plays audio resources for applications.
 *
 * <p>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.</p>
 *
 * <p>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.</p>
 *
 * <p>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.</p>
 *
 * <p>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.</p>
 *
 * <p>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.</p>
 *
 * <p>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.</p>
 *
 * <p>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.</p>
 *
 * <p>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 be 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.</p>
 *
 * <p>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.</p>
 */
public class SoundPool
{
    static { System.loadLibrary("soundpool"); }

    private final static String TAG = "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 WeakReference<SoundPool>(this), maxStreams, streamType, srcQuality);
    }

    /**
     * Load the sound from the specified path.
     *
     * @param path the path to the audio file
     * @param priority the priority of the sound. Currently has no effect. Use
     *                 a value of 1 for future compatibility.
     * @return a sound ID. This value can be used to play or unload the sound.
     */
    public int load(String path, int priority)
    {
        // pass network streams to player
        if (path.startsWith("http:"))
            return _load(path, priority);

        // try local path
        int id = 0;
        try {
            File f = new File(path);
            if (f != null) {
                ParcelFileDescriptor fd = ParcelFileDescriptor.open(f, ParcelFileDescriptor.MODE_READ_ONLY);
                if (fd != null) {
                    id = _load(fd.getFileDescriptor(), 0, f.length(), priority);
                    //Log.v(TAG, "close fd");
                    fd.close();
                }
            }
        } catch (java.io.IOException e) {}
        return id;
    }

    /**
     * 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.
     *
     * @param context the application context
     * @param resId the resource ID
     * @param priority the priority of the sound. Currently has no effect. Use
     *                 a value of 1 for future compatibility.
     * @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;
        if (afd != null) {
            id = _load(afd.getFileDescriptor(), afd.getStartOffset(), afd.getLength(), priority);
            try {
                //Log.v(TAG, "close fd");
                afd.close();
            } catch (java.io.IOException ex) {
                //Log.d(TAG, "close failed:", ex);
            }
        }
        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. Use
     *                 a value of 1 for future compatibility.
     * @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();
            if (len < 0) {
                throw new AndroidRuntimeException("no length for fd");
            }
            return _load(afd.getFileDescriptor(), afd.getStartOffset(), len, priority);
        } else {
            return 0;
        }
    }

    /**
     * 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. Use
     *                 a value of 1 for future compatibility.
     * @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);
    }

    private native final int _load(String uri, int priority);

    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. 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.
     *
     * @param soundID a soundID returned by the load() function
     * @param leftVolume left volume value (range = 0.0 to 1.0)
     * @param rightVolume right volume value (range = 0.0 to 1.0)
     * @param priority stream priority (0 = lowest priority)
     * @param loop loop mode (0 = no loop, -1 = loop forever)
     * @param rate playback rate (1.0 = normal playback, range 0.5 to 2.0)
     * @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. If the
     * stream does not exist, it will have no effect.
     *
     * @param streamID a streamID returned by the play() function
     */
    public native final void setPriority(int streamID, int priority);

    /**
     * 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.
     *
     * @param streamID a streamID returned by the play() function
     * @param loop loop mode (0 = no loop, -1 = loop forever)
     */
    public native final void setLoop(int streamID, int loop);

    /**
     * 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.
     *
     * @param streamID a streamID returned by the play() function
     * @param rate playback rate (1.0 = normal playback, range 0.5 to 2.0)
     */
    public native final void setRate(int streamID, float rate);

    /**
     * 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.
     */
    public native final void release();

    private native final void native_setup(Object mediaplayer_this,
            int maxStreams, int streamType, int srcQuality);

    protected void finalize() { release(); }
}