AI 146752: am: CL 146751 Finalize AudioTrack javadoc.
Original author: jmtrivi
Merged from: //branches/cupcake/...
Automated import of CL 146752
diff --git a/media/java/android/media/AudioTrack.java b/media/java/android/media/AudioTrack.java
index 4196ef39..3cd841d 100644
--- a/media/java/android/media/AudioTrack.java
+++ b/media/java/android/media/AudioTrack.java
@@ -32,22 +32,24 @@
* It allows to stream PCM audio buffers to the audio hardware for playback. This is
* achieved by "pushing" the data to the AudioTrack object using one of the
* {@link #write(byte[], int, int)} and {@link #write(short[], int, int)} methods.
- * <p>An AudioTrack instance can operate under two modes: static of streaming.<br>
- * The Streaming mode consists in continuously writing data to the AudioTrack, using one
- * of the write() methods. These are blocking and return when the data has been transferred
- * from the Java layer to the native layer, and is queued for playback. The streaming mode
+ *
+ * <p>An AudioTrack instance can operate under two modes: static or streaming.<br>
+ * In Streaming mode, the application writes a continuous stream of data to the AudioTrack, using
+ * one of the write() methods. These are blocking and return when the data has been transferred
+ * from the Java layer to the native layer and queued for playback. The streaming mode
* is most useful when playing blocks of audio data that for instance are:
* <ul>
* <li>too big to fit in memory because of the duration of the sound to play,</li>
* <li>too big to fit in memory because of the characteristics of the audio data
* (high sampling rate, bits per sample ...)</li>
- * <li>chosen, received or generated as the audio keeps playing.</li>
+ * <li>received or generated while previously queued audio is playing.</li>
* </ul>
* The static mode is to be chosen when dealing with short sounds that fit in memory and
- * that need to be played with the smallest latency possible. Static mode AudioTrack instances can
- * play the sound without the need to transfer the audio data from Java to the audio hardware
+ * that need to be played with the smallest latency possible. AudioTrack instances in static mode
+ * can play the sound without the need to transfer the audio data from Java to native layer
* each time the sound is to be played. The static mode will therefore be preferred for UI and
* game sounds that are played often, and with the smallest overhead possible.
+ *
* <p>Upon creation, an AudioTrack object initializes its associated audio buffer.
* The size of this buffer, specified during the construction, determines how long an AudioTrack
* can play before running out of data.<br>
@@ -66,11 +68,11 @@
/** Maximum value for a channel volume */
private static final float VOLUME_MAX = 1.0f;
- /** state of an AudioTrack this is stopped */
+ /** indicates AudioTrack state is stopped */
public static final int PLAYSTATE_STOPPED = 1; // matches SL_PLAYSTATE_STOPPED
- /** state of an AudioTrack this is paused */
+ /** indicates AudioTrack state is paused */
public static final int PLAYSTATE_PAUSED = 2; // matches SL_PLAYSTATE_PAUSED
- /** state of an AudioTrack this is playing */
+ /** indicates AudioTrack state is playing */
public static final int PLAYSTATE_PLAYING = 3; // matches SL_PLAYSTATE_PLAYING
/**
@@ -85,7 +87,7 @@
public static final int MODE_STREAM = 1;
/**
- * State of an AudioTrack that was not successfully initialized upon creation
+ * State of an AudioTrack that was not successfully initialized upon creation.
*/
public static final int STATE_UNINITIALIZED = 0;
/**
@@ -126,11 +128,11 @@
// Events:
// to keep in sync with frameworks/base/include/media/AudioTrack.h
/**
- * Event id for when the playback head has reached a previously set marker.
+ * Event id denotes when playback head has reached a previously set marker.
*/
private static final int NATIVE_EVENT_MARKER = 3;
/**
- * Event id for when the previously set update period has passed during playback.
+ * Event id denotes when previously set update period has elapsed during playback.
*/
private static final int NATIVE_EVENT_NEW_POS = 4;
@@ -141,11 +143,11 @@
// Member variables
//--------------------
/**
- * Indicates the state of the AudioTrack instance
+ * Indicates the state of the AudioTrack instance.
*/
private int mState = STATE_UNINITIALIZED;
/**
- * Indicates the play state of the AudioTrack instance
+ * Indicates the play state of the AudioTrack instance.
*/
private int mPlayState = PLAYSTATE_STOPPED;
/**
@@ -159,7 +161,7 @@
*/
private OnPlaybackPositionUpdateListener mPositionListener = null;
/**
- * Lock to protect event listener updates against event notifications
+ * Lock to protect event listener updates against event notifications.
*/
private final Object mPositionListenerLock = new Object();
/**
@@ -167,11 +169,11 @@
*/
private int mNativeBufferSizeInBytes = 0;
/**
- * Handler for marker events coming from the native code
+ * Handler for marker events coming from the native code.
*/
private NativeEventHandlerDelegate mEventHandlerDelegate = null;
/**
- * Looper associated with the thread that creates the AudioTrack instance
+ * Looper associated with the thread that creates the AudioTrack instance.
*/
private Looper mInitializationLooper = null;
/**
@@ -179,7 +181,7 @@
*/
private int mSampleRate = 22050;
/**
- * The number of input audio channels (1 is mono, 2 is stereo)
+ * The number of input audio channels (1 is mono, 2 is stereo).
*/
private int mChannelCount = 1;
/**
@@ -194,7 +196,7 @@
*/
private int mDataLoadMode = MODE_STREAM;
/**
- * The current audio channel configuration
+ * The current audio channel configuration.
*/
private int mChannelConfiguration = AudioFormat.CHANNEL_CONFIGURATION_MONO;
/**
@@ -209,7 +211,7 @@
// Used exclusively by native code
//--------------------
/**
- * Accessed by native methods: provides access to C++ AudioTrack object
+ * Accessed by native methods: provides access to C++ AudioTrack object.
*/
@SuppressWarnings("unused")
private int mNativeTrackInJavaObj;
@@ -227,17 +229,14 @@
/**
* Class constructor.
* @param streamType the type of the audio stream. See
-
* {@link AudioManager#STREAM_VOICE_CALL}, {@link AudioManager#STREAM_SYSTEM},
* {@link AudioManager#STREAM_RING}, {@link AudioManager#STREAM_MUSIC} and
* {@link AudioManager#STREAM_ALARM}
* @param sampleRateInHz the sample rate expressed in Hertz. Examples of rates are (but
* not limited to) 44100, 22050 and 11025.
* @param channelConfig describes the configuration of the audio channels.
-
* See {@link AudioFormat#CHANNEL_CONFIGURATION_MONO} and
* {@link AudioFormat#CHANNEL_CONFIGURATION_STEREO}
-
* @param audioFormat the format in which the audio data is represented.
* See {@link AudioFormat#ENCODING_PCM_16BIT} and
* {@link AudioFormat#ENCODING_PCM_8BIT}
@@ -245,6 +244,9 @@
* from for playback. If using the AudioTrack in streaming mode, you can write data into
* this buffer in smaller chunks than this size. If using the AudioTrack in static mode,
* this is the maximum size of the sound that will be played for this instance.
+ * See {@link #getMinBufferSize(int, int, int)} to determine the minimum required buffer size
+ * for the successful creation of an AudioTrack instance in streaming mode. Using values
+ * smaller than getMinBufferSize() will result in an initialization failure.
* @param mode streaming or static buffer. See {@link #MODE_STATIC} and {@link #MODE_STREAM}
* @throws java.lang.IllegalArgumentException
*/
@@ -423,8 +425,8 @@
}
/**
- * Returns the current playback rate in Hz. Note that this rate may differ from one set using
- * {@link #setPlaybackRate(int)} as the value effectively set is implementation-dependent.
+ * Returns the current playback rate in Hz. Note that this rate may differ from the one set
+ * with {@link #setPlaybackRate(int)} as the value effectively used is implementation-dependent.
*/
public int getPlaybackRate() {
return native_get_playback_rate();
@@ -470,6 +472,9 @@
* AudioTrack instance has been created to check if it was initialized
* properly. This ensures that the appropriate hardware resources have been
* acquired.
+ * @see #STATE_INITIALIZED
+ * @see #STATE_NO_STATIC_DATA
+ * @see #STATE_UNINITIALIZED
*/
public int getState() {
return mState;
@@ -486,28 +491,28 @@
}
/**
- * Returns the native frame count used by the hardware
+ * Returns the native frame count used by the hardware.
*/
protected int getNativeFrameCount() {
return native_get_native_frame_count();
}
/**
- * @return marker position in frames
+ * Returns marker position expressed in frames.
*/
public int getNotificationMarkerPosition() {
return native_get_marker_pos();
}
/**
- * @return update period in frames
+ * Returns the notification update period expressed in frames.
*/
public int getPositionNotificationPeriod() {
return native_get_pos_update_period();
}
/**
- * @return playback head position in frames
+ * Returns the playback head position expressed in frames
*/
public int getPlaybackHeadPosition() {
return native_get_position();
@@ -522,7 +527,9 @@
/**
* Returns the minimum buffer size required for the successful creation of an AudioTrack
- * object to be created in the {@link #MODE_STREAM} mode.
+ * object to be created in the {@link #MODE_STREAM} mode. Note that this size doesn't
+ * guarantee a smooth playback under load, and higher values should be chosen according to
+ * the expected frequency at which the buffer will be refilled with additional data to play.
* @param sampleRateInHz the sample rate expressed in Hertz.
* @param channelConfig describes the configuration of the audio channels.
* See {@link AudioFormat#CHANNEL_CONFIGURATION_MONO} and
@@ -533,7 +540,7 @@
* @return {@link #ERROR_BAD_VALUE} if an invalid parameter was passed,
* or {@link #ERROR} if the implementation was unable to query the hardware for its output
* properties,
- * or the minimum buffer size expressed in number of bytes.
+ * or the minimum buffer size expressed in bytes.
*/
static public int getMinBufferSize(int sampleRateInHz, int channelConfig, int audioFormat) {
int channelCount = 0;
@@ -577,13 +584,22 @@
/**
* Sets the listener the AudioTrack notifies when a previously set marker is reached or
* for each periodic playback head position update.
+ * Notifications will be received in the same thread as the one in which the AudioTrack
+ * instance was created.
* @param listener
*/
public void setPlaybackPositionUpdateListener(OnPlaybackPositionUpdateListener listener) {
setPlaybackPositionUpdateListener(listener, null);
}
-
+ /**
+ * Sets the listener the AudioTrack notifies when a previously set marker is reached or
+ * for each periodic playback head position update.
+ * Use this method to receive AudioTrack events in the Handler associated with another
+ * thread than the one in which you created the AudioTrack instance.
+ * @param listener
+ * @param handler the Handler that will receive the event notification messages.
+ */
public void setPlaybackPositionUpdateListener(OnPlaybackPositionUpdateListener listener,
Handler handler) {
synchronized (mPositionListenerLock) {
@@ -636,13 +652,17 @@
* the audio data will be consumed and played back, not the original sampling rate of the
* content. Setting it to half the sample rate of the content will cause the playback to
* last twice as long, but will also result result in a negative pitch shift.
- * The current implementation supports a maximum sample rate of twice the hardware output
- * sample rate (see {@link #getNativeOutputSampleRate(int)}). Use {@link #getSampleRate()} to
- * check the rate actually used in hardware after potential clamping.
- * @param sampleRateInHz
+ * The current implementation supports a maximum sample rate of 64kHz.
+ * Use {@link #getSampleRate()} to check the rate actually used in hardware after
+ * potential clamping.
+ * @param sampleRateInHz the sample rate expressed in Hz
* @return error code or success, see {@link #SUCCESS}, {@link #ERROR_BAD_VALUE},
* {@link #ERROR_INVALID_OPERATION}
*/
+ // FIXME: the implementation should support twice the hardware output sample rate
+ // (see {@link #getNativeOutputSampleRate(int)}), but currently
+ // due to the representation of the sample rate in the native layer, the sample rate
+ // is limited to 65535Hz
public int setPlaybackRate(int sampleRateInHz) {
if (mState != STATE_INITIALIZED) {
return ERROR_INVALID_OPERATION;
@@ -656,7 +676,7 @@
/**
- *
+ * Sets the position of the notification marker.
* @param markerInFrames marker in frames
* @return error code or success, see {@link #SUCCESS}, {@link #ERROR_BAD_VALUE},
* {@link #ERROR_INVALID_OPERATION}
@@ -670,7 +690,8 @@
/**
- * @param periodInFrames update period in frames
+ * Sets the period for the periodic notification event.
+ * @param periodInFrames update period expressed in frames
* @return error code or success, see {@link #SUCCESS}, {@link #ERROR_INVALID_OPERATION}
*/
public int setPositionNotificationPeriod(int periodInFrames) {
@@ -683,7 +704,7 @@
/**
* Sets the playback head position. The track must be stopped for the position to be changed.
- * @param positionInFrames playback head position in frames
+ * @param positionInFrames playback head position expressed in frames
* @return error code or success, see {@link #SUCCESS}, {@link #ERROR_BAD_VALUE},
* {@link #ERROR_INVALID_OPERATION}
*/
@@ -699,8 +720,8 @@
/**
* Sets the loop points and the loop count. The loop can be infinite.
- * @param startInFrames loop start marker in frames
- * @param endInFrames loop end marker in frames
+ * @param startInFrames loop start marker expressed in frames
+ * @param endInFrames loop end marker expressed in frames
* @param loopCount the number of times the loop is looped.
* A value of -1 means infinite looping.
* @return error code or success, see {@link #SUCCESS}, {@link #ERROR_BAD_VALUE},
@@ -797,7 +818,8 @@
/**
* Writes the audio data to the audio hardware for playback.
* @param audioData the array that holds the data to play.
- * @param offsetInBytes the offset in audioData where the data to play starts.
+ * @param offsetInBytes the offset expressed in bytes in audioData where the data to play
+ * starts.
* @param sizeInBytes the number of bytes to read in audioData after the offset.
* @return the number of bytes that were written or {@link #ERROR_INVALID_OPERATION}
* if the object wasn't properly initialized, or {@link #ERROR_BAD_VALUE} if
@@ -827,7 +849,8 @@
/**
* Writes the audio data to the audio hardware for playback.
* @param audioData the array that holds the data to play.
- * @param offsetInShorts the offset in audioData where the data to play starts.
+ * @param offsetInShorts the offset expressed in shorts in audioData where the data to play
+ * starts.
* @param sizeInShorts the number of bytes to read in audioData after the offset.
* @return the number of shorts that were written or {@link #ERROR_INVALID_OPERATION}
* if the object wasn't properly initialized, or {@link #ERROR_BAD_VALUE} if
