MediaSync
class MediaSync
kotlin.Any | |
↳ | android.media.MediaSync |
MediaSync class can be used to synchronously play audio and video streams. It can be used to play audio-only or video-only stream, too.
MediaSync is generally used like this:
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); // ... }
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 android.media.AudioTrack#MODE_STREAM
. The audio buffers are sent to MediaSync directly via queueAudio
, and are returned to the client via Callback#onAudioBufferConsumed
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.
Summary
Nested classes | |
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abstract |
MediaSync callback interface. |
abstract |
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 | |
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static Int |
Audio track failed. |
static Int |
The surface failed to handle video buffers. |
Public constructors | |
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Class constructor. |
Public methods | |
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Surface |
Requests a Surface to use as the input. |
Unit |
flush() Flushes all buffers from the sync object. |
PlaybackParams |
Gets the playback rate using |
SyncParams |
Gets the A/V sync mode. |
MediaTimestamp? |
Get current playback position. |
Unit |
queueAudio(audioData: ByteBuffer, bufferId: Int, presentationTimeUs: Long) Queues the audio data asynchronously for playback (AudioTrack must be in streaming mode). |
Unit |
release() 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. |
Unit |
setAudioTrack(audioTrack: AudioTrack?) Sets the audio track for MediaSync. |
Unit |
setCallback(cb: MediaSync.Callback?, handler: Handler?) Sets an asynchronous callback for actionable MediaSync events. |
Unit |
setOnErrorListener(listener: MediaSync.OnErrorListener?, handler: Handler?) Sets an asynchronous callback for error events. |
Unit |
setPlaybackParams(params: PlaybackParams) Sets playback rate using |
Unit |
setSurface(surface: Surface?) Sets the output surface for MediaSync. |
Unit |
setSyncParams(params: SyncParams) Sets A/V sync mode. |
Protected methods | |
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Unit |
finalize() |
Constants
MEDIASYNC_ERROR_AUDIOTRACK_FAIL
static val MEDIASYNC_ERROR_AUDIOTRACK_FAIL: Int
Audio track failed.
Value: 1
MEDIASYNC_ERROR_SURFACE_FAIL
static val MEDIASYNC_ERROR_SURFACE_FAIL: Int
The surface failed to handle video buffers.
Value: 2
Public constructors
MediaSync
MediaSync()
Class constructor. On creation, MediaSync is paused, i.e., playback rate is 0.0f.
Public methods
createInputSurface
fun createInputSurface(): Surface
Requests a Surface to use as the input. This may only be called after setSurface
.
The application is responsible for calling release() on the Surface when done.
Return | |
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Surface |
This value cannot be null . |
Exceptions | |
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java.lang.IllegalStateException |
if not set, or another input surface has already been created. |
flush
fun flush(): Unit
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.
Exceptions | |
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java.lang.IllegalStateException |
if the internal player engine has not been initialized. |
getPlaybackParams
fun getPlaybackParams(): PlaybackParams
Gets the playback rate using PlaybackParams
.
Return | |
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PlaybackParams |
the playback rate being used. This value cannot be null . |
Exceptions | |
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java.lang.IllegalStateException |
if the internal sync engine or the audio track has not been initialized. |
getSyncParams
fun getSyncParams(): SyncParams
Gets the A/V sync mode.
Return | |
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SyncParams |
the A/V sync params This value cannot be null . |
Exceptions | |
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java.lang.IllegalStateException |
if the internal player engine has not been initialized. |
getTimestamp
fun getTimestamp(): MediaTimestamp?
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 MediaTimestamp#getAnchorMediaTimeUs
can be used as current playback position.
Return | |
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MediaTimestamp? |
a MediaTimestamp object if a timestamp is available, or null if no timestamp is available, e.g. because the media player has not been initialized. |
See Also
queueAudio
fun queueAudio(
audioData: ByteBuffer,
bufferId: Int,
presentationTimeUs: Long
): Unit
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.
Parameters | |
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audioData |
ByteBuffer: the buffer that holds the data to play. This buffer will be returned to the client via registered callback. This value cannot be null . |
bufferId |
Int: 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 |
Long: the presentation timestamp in microseconds for the first frame in the buffer. |
Exceptions | |
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java.lang.IllegalStateException |
if audio track is not set or internal configureation has not been done correctly. |
release
fun release(): Unit
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.
setAudioTrack
fun setAudioTrack(audioTrack: AudioTrack?): Unit
Sets the audio track for MediaSync.
Currently, this is only supported in the Initialized state.
Parameters | |
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audioTrack |
AudioTrack?: Specify an AudioTrack through which to render the audio data. This value may be null . |
Exceptions | |
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java.lang.IllegalArgumentException |
if the audioTrack has been released, or is invalid. |
java.lang.IllegalStateException |
if setting the audio track is not supported, e.g. not in the Initialized state, or another audio track has already been set. |
setCallback
fun setCallback(
cb: MediaSync.Callback?,
handler: Handler?
): Unit
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.
Parameters | |
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cb |
MediaSync.Callback?: The callback that will run. Use null to stop receiving callbacks. |
handler |
Handler?: The Handler that will run the callback. Use null to use MediaSync's internal handler if it exists. |
setOnErrorListener
fun setOnErrorListener(
listener: MediaSync.OnErrorListener?,
handler: Handler?
): Unit
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.
Parameters | |
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listener |
MediaSync.OnErrorListener?: The callback that will run. Use null to stop receiving callbacks. |
handler |
Handler?: The Handler that will run the callback. Use null to use MediaSync's internal handler if it exists. |
setPlaybackParams
fun setPlaybackParams(params: PlaybackParams): Unit
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.
Parameters | |
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params |
PlaybackParams: 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. This value cannot be null . |
Exceptions | |
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java.lang.IllegalStateException |
if the internal sync engine or the audio track has not been initialized. |
java.lang.IllegalArgumentException |
if the params are not supported. |
setSurface
fun setSurface(surface: Surface?): Unit
Sets the output surface for MediaSync.
Currently, this is only supported in the Initialized state.
Parameters | |
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surface |
Surface?: Specify a surface on which to render the video data. This value may be null . |
Exceptions | |
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java.lang.IllegalArgumentException |
if the surface has been released, is invalid, or can not be connected. |
java.lang.IllegalStateException |
if setting the surface is not supported, e.g. not in the Initialized state, or another surface has already been set. |
setSyncParams
fun setSyncParams(params: SyncParams): Unit
Sets A/V sync mode.
Parameters | |
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params |
SyncParams: the A/V sync params to apply This value cannot be null . |
Exceptions | |
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java.lang.IllegalStateException |
if the internal player engine has not been initialized. |
java.lang.IllegalArgumentException |
if params are not supported. |
Protected methods
finalize
protected fun finalize(): Unit
Exceptions | |
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java.lang.Throwable |
the Exception raised by this method |