Added in API level 23

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);
      // ...
  }
 
  
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 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
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
static Int

Audio track failed.

static Int

The surface failed to handle video buffers.

Public constructors

Class constructor.

Public methods
Surface

Requests a Surface to use as the input.

Unit

Flushes all buffers from the sync object.

PlaybackParams

Gets the playback rate using PlaybackParams.

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

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

Sets an asynchronous callback for actionable MediaSync events.

Unit

Sets an asynchronous callback for error events.

Unit

Sets playback rate using PlaybackParams.

Unit
setSurface(surface: Surface?)

Sets the output surface for MediaSync.

Unit

Sets A/V sync mode.

Protected methods
Unit

Constants

MEDIASYNC_ERROR_AUDIOTRACK_FAIL

Added in API level 23
static val MEDIASYNC_ERROR_AUDIOTRACK_FAIL: Int

Audio track failed.

Value: 1

MEDIASYNC_ERROR_SURFACE_FAIL

Added in API level 23
static val MEDIASYNC_ERROR_SURFACE_FAIL: Int

The surface failed to handle video buffers.

Value: 2

Public constructors

MediaSync

Added in API level 23
MediaSync()

Class constructor. On creation, MediaSync is paused, i.e., playback rate is 0.0f.

Public methods

createInputSurface

Added in API level 23
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
Surface This value cannot be null.
Exceptions
java.lang.IllegalStateException if not set, or another input surface has already been created.

flush

Added in API level 23
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
java.lang.IllegalStateException if the internal player engine has not been initialized.

getPlaybackParams

Added in API level 23
fun getPlaybackParams(): PlaybackParams

Gets the playback rate using PlaybackParams.

Return
PlaybackParams the playback rate being used. This value cannot be null.
Exceptions
java.lang.IllegalStateException if the internal sync engine or the audio track has not been initialized.

getSyncParams

Added in API level 23
fun getSyncParams(): SyncParams

Gets the A/V sync mode.

Return
SyncParams the A/V sync params This value cannot be null.
Exceptions
java.lang.IllegalStateException if the internal player engine has not been initialized.

getTimestamp

Added in API level 23
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
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.

queueAudio

Added in API level 23
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
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
java.lang.IllegalStateException if audio track is not set or internal configureation has not been done correctly.

release

Added in API level 23
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

Added in API level 23
fun setAudioTrack(audioTrack: AudioTrack?): Unit

Sets the audio track for MediaSync.

Currently, this is only supported in the Initialized state.

Parameters
audioTrack AudioTrack?: Specify an AudioTrack through which to render the audio data. This value may be null.
Exceptions
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

Added in API level 23
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
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

Added in API level 23
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
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

Added in API level 23
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
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
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

Added in API level 23
fun setSurface(surface: Surface?): Unit

Sets the output surface for MediaSync.

Currently, this is only supported in the Initialized state.

Parameters
surface Surface?: Specify a surface on which to render the video data. This value may be null.
Exceptions
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

Added in API level 23
fun setSyncParams(params: SyncParams): Unit

Sets A/V sync mode.

Parameters
params SyncParams: the A/V sync params to apply This value cannot be null.
Exceptions
java.lang.IllegalStateException if the internal player engine has not been initialized.
java.lang.IllegalArgumentException if params are not supported.

Protected methods

finalize

Added in API level 23
protected fun finalize(): Unit
Exceptions
java.lang.Throwable the Exception raised by this method