Stop enqueueing data to output audio device if consecutive empty buffers are received

media/audio/android/opensles_output.cc

Index: media/audio/android/opensles_output.cc
diff --git a/media/audio/android/opensles_output.cc b/media/audio/android/opensles_output.cc
index 2974e1418ca57454bfeff4c5abbfba4631860015..8587182efb4e67766097bf1b8aa76f8867e80ddb 100644
--- a/media/audio/android/opensles_output.cc
+++ b/media/audio/android/opensles_output.cc
@@ -5,6 +5,8 @@
 #include "media/audio/android/opensles_output.h"
 
 #include "base/logging.h"
+#include "base/single_thread_task_runner.h"
+#include "base/thread_task_runner_handle.h"
 #include "base/trace_event/trace_event.h"
 #include "media/audio/android/audio_manager_android.h"
 
@@ -19,6 +21,11 @@
 
 namespace media {
 
+// Threshold for consecutive number of empty buffers to let the player enter
+// idle state.
+// TODO(qinmin): change this threshold to count the number of frames.
+static const int kEmptyBufferThreasholdForIdleMode = 2;
+
 OpenSLESOutputStream::OpenSLESOutputStream(AudioManagerAndroid* manager,
                                            const AudioParameters& params,
                                            SLint32 stream_type)
@@ -31,7 +38,10 @@ OpenSLESOutputStream::OpenSLESOutputStream(AudioManagerAndroid* manager,
       buffer_size_bytes_(0),
       started_(false),
       muted_(false),
-      volume_(1.0) {
+      volume_(1.0),
+      consecutive_empty_buffer_count_(0),
+      task_runner_(base::ThreadTaskRunnerHandle::Get()),
+      weak_factory_(this) {
   DVLOG(2) << "OpenSLESOutputStream::OpenSLESOutputStream("
            << "stream_type=" << stream_type << ")";
   format_.formatType = SL_DATAFORMAT_PCM;
@@ -52,6 +62,8 @@ OpenSLESOutputStream::OpenSLESOutputStream(AudioManagerAndroid* manager,
   audio_bus_ = AudioBus::Create(params);
 
   memset(&audio_data_, 0, sizeof(audio_data_));
+  weak_this_ = weak_factory_.GetWeakPtr();
+  audio_timestamp_helper_.reset(new AudioTimestampHelper(params.sample_rate()));
 }
 
 OpenSLESOutputStream::~OpenSLESOutputStream() {
@@ -95,7 +107,7 @@ void OpenSLESOutputStream::Start(AudioSourceCallback* callback) {
 
   // Avoid start-up glitches by filling up one buffer queue before starting
   // the stream.
-  FillBufferQueueNoLock();
+  FillBufferQueueNoLock(false);
 
   // Start streaming data by setting the play state to SL_PLAYSTATE_PLAYING.
   // For a player object, when the object is in the SL_PLAYSTATE_PLAYING
@@ -134,6 +146,8 @@ void OpenSLESOutputStream::Stop() {
 
   callback_ = NULL;
   started_ = false;
+  CancelIdleCheck();
+  consecutive_empty_buffer_count_ = 0;
 }
 
 void OpenSLESOutputStream::Close() {
@@ -167,14 +181,12 @@ void OpenSLESOutputStream::SetVolume(double volume) {
   DCHECK(thread_checker_.CalledOnValidThread());
 
   double volume_override = 0;
-  if (audio_manager_->HasOutputVolumeOverride(&volume_override)) {
+  if (audio_manager_->HasOutputVolumeOverride(&volume_override))
     volume = volume_override;
-  }
 
   float volume_float = static_cast<float>(volume);
-  if (volume_float < 0.0f || volume_float > 1.0f) {
+  if (volume_float < 0.0f || volume_float > 1.0f)
     return;
-  }
   volume_ = volume_float;
 }
 
@@ -319,10 +331,10 @@ void OpenSLESOutputStream::FillBufferQueue() {
 
   // Fill up one buffer in the queue by asking the registered source for
   // data using the OnMoreData() callback.
-  FillBufferQueueNoLock();
+  FillBufferQueueNoLock(false);
 }
 
-void OpenSLESOutputStream::FillBufferQueueNoLock() {
+void OpenSLESOutputStream::FillBufferQueueNoLock(bool in_idle_mode) {
   // Ensure that the calling thread has acquired the lock since it is not
   // done in this method.
   lock_.AssertAcquired();
@@ -331,13 +343,24 @@ void OpenSLESOutputStream::FillBufferQueueNoLock() {
   // TODO(henrika): Investigate if it is possible to get a more accurate
   // delay estimation.
   const uint32 hardware_delay = buffer_size_bytes_;
-  int frames_filled = callback_->OnMoreData(
-      audio_bus_.get(), hardware_delay);
+  int frames_filled = callback_->OnMoreData(audio_bus_.get(), hardware_delay);
   if (frames_filled <= 0) {
     // Audio source is shutting down, or halted on error.
     return;
   }
 
+  // Skip enqueueing data if the output is empty to save power.
+  if (audio_bus_->AreFramesZero()) {
+    // TODO(qinmin): check if this variable overflows.
+    consecutive_empty_buffer_count_++;
+    if (consecutive_empty_buffer_count_ >= kEmptyBufferThreasholdForIdleMode) {
+      WaitingForAudio(in_idle_mode, frames_filled, base::TimeTicks::Now());
+      return;
+    }
+  } else {
+    consecutive_empty_buffer_count_ = 0;
+  }
+
   // Note: If the internal representation ever changes from 16-bit PCM to
   // raw float, the data must be clipped and sanitized since it may come
   // from an untrusted source such as NaCl.
@@ -364,9 +387,8 @@ void OpenSLESOutputStream::FillBufferQueueNoLock() {
 void OpenSLESOutputStream::SetupAudioBuffer() {
   DCHECK(thread_checker_.CalledOnValidThread());
   DCHECK(!audio_data_[0]);
-  for (int i = 0; i < kMaxNumOfBuffersInQueue; ++i) {
+  for (int i = 0; i < kMaxNumOfBuffersInQueue; ++i)
     audio_data_[i] = new uint8[buffer_size_bytes_];
-  }
 }
 
 void OpenSLESOutputStream::ReleaseAudioBuffer() {
@@ -383,6 +405,55 @@ void OpenSLESOutputStream::HandleError(SLresult error) {
   DLOG(ERROR) << "OpenSLES Output error " << error;
   if (callback_)
     callback_->OnError(this);
+  CancelIdleCheck();
+}
+
+void OpenSLESOutputStream::CheckForIdle() {
+  DCHECK(thread_checker_.CalledOnValidThread());
+  DCHECK(!idle_check_callback_.IsCancelled());
+
+  if (!started_)
+    return;
+  base::AutoLock lock(lock_);
+  FillBufferQueueNoLock(true);
+}
+
+void OpenSLESOutputStream::CancelIdleCheck() {
+  if (!task_runner_->BelongsToCurrentThread()) {
+    task_runner_->PostTask(
+        FROM_HERE,
+        base::Bind(&OpenSLESOutputStream::CancelIdleCheck, weak_this_));
+    return;
+  }
+  idle_check_callback_.Cancel();
+}
+
+void OpenSLESOutputStream::WaitingForAudio(
+    bool in_idle_mode, int frames_filled, base::TimeTicks idle_start_time) {
+  if (!task_runner_->BelongsToCurrentThread()) {
+    task_runner_->PostTask(
+        FROM_HERE,
+        base::Bind(&OpenSLESOutputStream::WaitingForAudio,
+                   weak_this_, in_idle_mode, frames_filled, idle_start_time));
+    return;
+  }
+
+  if (!in_idle_mode) {
+    audio_timestamp_helper_->SetBaseTimestamp(base::TimeDelta());
+    idle_start_time_ = idle_start_time;
+    idle_check_callback_.Reset(
+        base::Bind(&OpenSLESOutputStream::CheckForIdle, weak_this_));
+  }
+
+  audio_timestamp_helper_->AddFrames(frames_filled);
+  base::TimeDelta delay_to_next_read = audio_timestamp_helper_->GetTimestamp() +
+      (idle_start_time_ - base::TimeTicks::Now());
+  if (delay_to_next_read < base::TimeDelta())
+    delay_to_next_read = base::TimeDelta();
+  task_runner_->PostDelayedTask(
+      FROM_HERE,
+      idle_check_callback_.callback(),
+      delay_to_next_read);
 }
 
 }  // namespace media