Compute sleep time when AudioTrack client callback returns no PCM data
Callbacks can go into a sleep-wait cycle if the client/app is unable to
deliver data. This can happen if the buffer is large, or if
the client/app cannot keep the buffer filled, or upon a stream end condition.
We improve the sleep time computation for AudioTrack PCM callbacks.
This minimizes the number of callbacks to NuPlayerRenderer.
Bug: 21198655
Change-Id: I4247798a6638def2f0d8f1b46f60323482065cb2
diff --git a/include/media/AudioTrack.h b/include/media/AudioTrack.h
index 3efa74c..ec16933 100644
--- a/include/media/AudioTrack.h
+++ b/include/media/AudioTrack.h
@@ -43,22 +43,30 @@
*/
enum event_type {
EVENT_MORE_DATA = 0, // Request to write more data to buffer.
+ // This event only occurs for TRANSFER_CALLBACK.
// If this event is delivered but the callback handler
- // does not want to write more data, the handler must explicitly
+ // does not want to write more data, the handler must
// ignore the event by setting frameCount to zero.
- EVENT_UNDERRUN = 1, // Buffer underrun occurred.
+ // This might occur, for example, if the application is
+ // waiting for source data or is at the end of stream.
+ //
+ // For data filling, it is preferred that the callback
+ // does not block and instead returns a short count on
+ // the amount of data actually delivered
+ // (or 0, if no data is currently available).
+ EVENT_UNDERRUN = 1, // Buffer underrun occurred. This will not occur for
+ // static tracks.
EVENT_LOOP_END = 2, // Sample loop end was reached; playback restarted from
- // loop start if loop count was not 0.
+ // loop start if loop count was not 0 for a static track.
EVENT_MARKER = 3, // Playback head is at the specified marker position
// (See setMarkerPosition()).
EVENT_NEW_POS = 4, // Playback head is at a new position
// (See setPositionUpdatePeriod()).
- EVENT_BUFFER_END = 5, // Playback head is at the end of the buffer.
- // Not currently used by android.media.AudioTrack.
+ EVENT_BUFFER_END = 5, // Playback has completed for a static track.
EVENT_NEW_IAUDIOTRACK = 6, // IAudioTrack was re-created, either due to re-routing and
// voluntary invalidation by mediaserver, or mediaserver crash.
EVENT_STREAM_END = 7, // Sent after all the buffers queued in AF and HW are played
- // back (after stop is called)
+ // back (after stop is called) for an offloaded track.
#if 0 // FIXME not yet implemented
EVENT_NEW_TIMESTAMP = 8, // Delivered periodically and when there's a significant change
// in the mapping from frame position to presentation time.