| java.lang.Object | |
| ↳ | android.media.MediaSync |
MediaSync class can be used to synchronously playback audio and video streams. It can be used to play audio-only or video-only stream, too.
MediaSync is generally used like this:
Developers
MediaSync sync = new MediaSync();
sync.setSurface(surface);
Surface inputSurface = sync.createInputSurface();
...
// MediaCodec videoDecoder = ...;
videoDecoder.configure(format, inputSurface, ...);
...
sync.setAudioTrack(audioTrack);
sync.setCallback(new MediaSync.Callback() {
@Override
public void onAudioBufferConsumed(MediaSync sync, ByteBuffer audioBuffer, int bufferId) {
...
}
}, null);
// This needs to be done since sync is paused on creation.
sync.setPlaybackParams(new PlaybackParams().setSpeed(1.f));
for (;;) {
...
// send video frames to surface for rendering, e.g., call
// videoDecoder.releaseOutputBuffer(videoOutputBufferIx, videoPresentationTimeNs);
// More details are available as below.
...
sync.queueAudio(audioByteBuffer, bufferId, audioPresentationTimeUs); // non-blocking.
// The audioByteBuffer and bufferId will be returned via callback.
// More details are available as below.
...
...
}
sync.setPlaybackParams(new PlaybackParams().setSpeed(0.f));
sync.release();
sync = null;
// The following code snippet illustrates how video/audio raw frames are created by
// MediaCodec's, how they are fed to MediaSync and how they are returned by MediaSync.
// This is the callback from MediaCodec.
onOutputBufferAvailable(MediaCodec codec, int bufferId, BufferInfo info) {
// ...
if (codec == videoDecoder) {
// surface timestamp must contain media presentation time in nanoseconds.
codec.releaseOutputBuffer(bufferId, 1000 * info.presentationTime);
} else {
ByteBuffer audioByteBuffer = codec.getOutputBuffer(bufferId);
sync.queueAudio(audioByteBuffer, bufferId, info.presentationTime);
}
// ...
}
// This is the callback from MediaSync.
onAudioBufferConsumed(MediaSync sync, ByteBuffer buffer, int bufferId) {
// ...
audioDecoder.releaseBuffer(bufferId, false);
// ...
}
The client needs to configure corresponding sink by setting the Surface and/or AudioTrack
based on the stream type it will play.
For video, the client needs to call createInputSurface() to obtain a surface on
which it will render video frames.
For audio, the client needs to set up audio track correctly, e.g., using MODE_STREAM. The audio buffers are sent to MediaSync directly via queueAudio(ByteBuffer, int, long), and are returned to the client via onAudioBufferConsumed(MediaSync, ByteBuffer, int)
asynchronously. The client should not modify an audio buffer till it's returned.
The client can optionally pre-fill audio/video buffers by setting playback rate to 0.0, and then feed audio/video buffers to corresponding components. This can reduce possible initial underrun.
| Nested Classes | |||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|
| MediaSync.Callback | MediaSync callback interface. | ||||||||||
| MediaSync.OnErrorListener | Interface definition of a callback to be invoked when there has been an error during an asynchronous operation (other errors will throw exceptions at method call time). | ||||||||||
| Constants | |||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|
| int | MEDIASYNC_ERROR_AUDIOTRACK_FAIL | Audio track failed. | |||||||||
| int | MEDIASYNC_ERROR_SURFACE_FAIL | The surface failed to handle video buffers. | |||||||||
| Public Constructors | |||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|
Class constructor.
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| Public Methods | |||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|
Requests a Surface to use as the input.
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Flushes all buffers from the sync object.
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Gets the playback rate using
PlaybackParams.
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Gets the A/V sync mode.
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Get current playback position.
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Queues the audio data asynchronously for playback (AudioTrack must be in streaming mode).
| |||||||||||
Make sure you call this when you're done to free up any opened
component instance instead of relying on the garbage collector
to do this for you at some point in the future.
| |||||||||||
Sets the audio track for MediaSync.
| |||||||||||
Sets an asynchronous callback for actionable MediaSync events.
| |||||||||||
Sets an asynchronous callback for error events.
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Sets playback rate using
PlaybackParams.
| |||||||||||
Sets the output surface for MediaSync.
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Sets A/V sync mode.
| |||||||||||
| Protected Methods | |||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|
Invoked when the garbage collector has detected that this instance is no longer reachable.
| |||||||||||
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[Expand]
Inherited Methods | |||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|
From class
java.lang.Object
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The surface failed to handle video buffers.
Class constructor. On creation, MediaSync is paused, i.e., playback rate is 0.0f.
Requests a Surface to use as the input. This may only be called after
setSurface(Surface).
The application is responsible for calling release() on the Surface when done.
| IllegalStateException | if not set, or another input surface has already been created. |
|---|
Flushes all buffers from the sync object.
All pending unprocessed audio and video buffers are discarded. If an audio track was configured, it is flushed and stopped. If a video output surface was configured, the last frame queued to it is left on the frame. Queue a blank video frame to clear the surface,
No callbacks are received for the flushed buffers.
| IllegalStateException | if the internal player engine has not been initialized. |
|---|
Gets the playback rate using PlaybackParams.
| IllegalStateException | if the internal sync engine or the audio track has not been initialized. |
|---|
Gets the A/V sync mode.
| IllegalStateException | if the internal player engine has not been initialized. |
|---|
Get current playback position.
The MediaTimestamp represents how the media time correlates to the system time in a linear fashion using an anchor and a clock rate. During regular playback, the media time moves fairly constantly (though the anchor frame may be rebased to a current system time, the linear correlation stays steady). Therefore, this method does not need to be called often.
To help users get current playback position, this method always anchors the timestamp
to the current system time, so
getAnchorMediaTimeUs() can be used as current playback position.
null if no timestamp
is available, e.g. because the media player has not been initialized.Queues the audio data asynchronously for playback (AudioTrack must be in streaming mode).
If the audio track was flushed as a result of flush(), it will be restarted.
| audioData | the buffer that holds the data to play. This buffer will be returned to the client via registered callback. |
|---|---|
| bufferId | an integer used to identify audioData. It will be returned to the client along with audioData. This helps applications to keep track of audioData, e.g., it can be used to store the output buffer index used by the audio codec. |
| presentationTimeUs | the presentation timestamp in microseconds for the first frame in the buffer. |
| IllegalStateException | if audio track is not set or internal configureation has not been done correctly. |
|---|
Make sure you call this when you're done to free up any opened component instance instead of relying on the garbage collector to do this for you at some point in the future.
Sets the audio track for MediaSync.
Currently, this is only supported in the Initialized state.
| audioTrack | Specify an AudioTrack through which to render the audio data. |
|---|
| IllegalArgumentException | if the audioTrack has been released, or is invalid. |
|---|---|
| IllegalStateException | if setting the audio track is not supported, e.g. not in the Initialized state, or another audio track has already been set. |
Sets an asynchronous callback for actionable MediaSync events.
This method can be called multiple times to update a previously set callback. If the handler is changed, undelivered notifications scheduled for the old handler may be dropped.
Do not call this inside callback.
| cb | The callback that will run. Use null to stop receiving callbacks. |
|---|---|
| handler | The Handler that will run the callback. Use null to use MediaSync's
internal handler if it exists.
|
Sets an asynchronous callback for error events.
This method can be called multiple times to update a previously set listener. If the handler is changed, undelivered notifications scheduled for the old handler may be dropped.
Do not call this inside callback.
| listener | The callback that will run. Use null to stop receiving callbacks. |
|---|---|
| handler | The Handler that will run the callback. Use null to use MediaSync's
internal handler if it exists.
|
Sets playback rate using PlaybackParams.
When using MediaSync with AudioTrack, set playback params using this
call instead of calling it directly on the track, so that the sync is aware of
the params change.
This call also works if there is no audio track.
| params | the playback params to use. Speed is the ratio between desired playback rate and normal one. 1.0 means
normal playback speed. 0.0 means pause. Value larger than 1.0 means faster playback,
while value between 0.0 and 1.0 for slower playback. Note: the normal rate
does not change as a result of this call. To restore the original rate at any time,
use speed of 1.0. |
|---|
| IllegalStateException | if the internal sync engine or the audio track has not been initialized. |
|---|---|
| IllegalArgumentException | if the params are not supported. |
Sets the output surface for MediaSync.
Currently, this is only supported in the Initialized state.
| surface | Specify a surface on which to render the video data. |
|---|
| IllegalArgumentException | if the surface has been released, is invalid, or can not be connected. |
|---|---|
| IllegalStateException | if setting the surface is not supported, e.g. not in the Initialized state, or another surface has already been set. |
Sets A/V sync mode.
| params | the A/V sync params to apply |
|---|
| IllegalStateException | if the internal player engine has not been initialized. |
|---|---|
| IllegalArgumentException | if params are not supported. |
Invoked when the garbage collector has detected that this instance is no longer reachable. The default implementation does nothing, but this method can be overridden to free resources.
Note that objects that override finalize are significantly more expensive than
objects that don't. Finalizers may be run a long time after the object is no longer
reachable, depending on memory pressure, so it's a bad idea to rely on them for cleanup.
Note also that finalizers are run on a single VM-wide finalizer thread,
so doing blocking work in a finalizer is a bad idea. A finalizer is usually only necessary
for a class that has a native peer and needs to call a native method to destroy that peer.
Even then, it's better to provide an explicit close method (and implement
Closeable), and insist that callers manually dispose of instances. This
works well for something like files, but less well for something like a BigInteger
where typical calling code would have to deal with lots of temporaries. Unfortunately,
code that creates lots of temporaries is the worst kind of code from the point of view of
the single finalizer thread.
If you must use finalizers, consider at least providing your own
ReferenceQueue and having your own thread process that queue.
Unlike constructors, finalizers are not automatically chained. You are responsible for
calling super.finalize() yourself.
Uncaught exceptions thrown by finalizers are ignored and do not terminate the finalizer thread. See Effective Java Item 7, "Avoid finalizers" for more.