Move audibility detection to BaseAudioContext

Have the BaseAudioContext do the audibility detection instead of the
AudioDestination.  And also post a task to the main thread when
audible audio starts or stops.  This is in preparation for reporting
this information to the browser.

Bug: 855069
Test: 
Change-Id: I8abd9be664697e8cc02998daec06f9ca0d34a98d
Reviewed-on: https://chromium-review.googlesource.com/1165947Reviewed-by: Hongchan Choi <hongchan@chromium.org>
Commit-Queue: Raymond Toy <rtoy@chromium.org>
Cr-Commit-Position: refs/heads/master@{#582029}

third_party/blink/renderer/modules/webaudio/base_audio_context.cc

@@ -69,16 +69,21 @@
 #include "third_party/blink/renderer/modules/webaudio/script_processor_node.h"
 #include "third_party/blink/renderer/modules/webaudio/stereo_panner_node.h"
 #include "third_party/blink/renderer/modules/webaudio/wave_shaper_node.h"
-#include "third_party/blink/renderer/platform/uuid.h"
 #include "third_party/blink/renderer/platform/audio/iir_filter.h"
+#include "third_party/blink/renderer/platform/audio/vector_math.h"
 #include "third_party/blink/renderer/platform/bindings/exception_state.h"
 #include "third_party/blink/renderer/platform/bindings/script_state.h"
 #include "third_party/blink/renderer/platform/cross_thread_functional.h"
 #include "third_party/blink/renderer/platform/histogram.h"
+#include "third_party/blink/renderer/platform/uuid.h"
 #include "third_party/blink/renderer/platform/wtf/text/wtf_string.h"
 
 namespace blink {
 
+// Recording of audio audibility stops after the context has been running for
+// this long.  We don't need this information for the lifetime of the context.
+const double kStopRecordingAudibilityTime = 10;
+
 BaseAudioContext* BaseAudioContext::Create(
     Document& document,
     const AudioContextOptions& context_options,
@@ -695,7 +700,24 @@ void BaseAudioContext::HandlePreRenderTasks(
   }
 }
 
-void BaseAudioContext::HandlePostRenderTasks() {
+// Determine if the rendered data is audible.
+static bool IsAudible(const AudioBus* rendered_data) {
+  // Compute the energy in each channel and sum up the energy in each channel
+  // for the total energy.
+  float energy = 0;
+
+  unsigned data_size = rendered_data->length();
+  for (unsigned k = 0; k < rendered_data->NumberOfChannels(); ++k) {
+    const float* data = rendered_data->Channel(k)->Data();
+    float channel_energy;
+    VectorMath::Vsvesq(data, 1, &channel_energy, data_size);
+    energy += channel_energy;
+  }
+
+  return energy > 0;
+}
+
+void BaseAudioContext::HandlePostRenderTasks(const AudioBus* destination_bus) {
   DCHECK(IsAudioThread());
 
   // Must use a tryLock() here too.  Don't worry, the lock will very rarely be
@@ -712,6 +734,37 @@ void BaseAudioContext::HandlePostRenderTasks() {
 
     unlock();
   }
+
+  // Notify browser if audible audio has started or stopped.
+  if (HasRealtimeConstraint()) {
+    // Detect silence (or not) for MEI
+    bool is_audible = IsAudible(destination_bus);
+
+    // We want to keep track of the total audible audio, but we don't need to
+    // record the start and stop of audible audio after
+    // |kStopRecordingAudibilityTime|.
+    if (is_audible) {
+      ++total_audible_renders_;
+    }
+
+    if (currentTime() <= kStopRecordingAudibilityTime) {
+      if (was_audible_ != is_audible) {
+        // Audibility changed in this render, so report the change.
+        was_audible_ = is_audible;
+        if (is_audible) {
+          PostCrossThreadTask(
+              *Platform::Current()->MainThread()->GetTaskRunner(), FROM_HERE,
+              CrossThreadBind(&BaseAudioContext::NotifyAudibleAudioStarted,
+                              WrapCrossThreadPersistent(this)));
+        } else {
+          PostCrossThreadTask(
+              *Platform::Current()->MainThread()->GetTaskRunner(), FROM_HERE,
+              CrossThreadBind(&BaseAudioContext::NotifyAudibleAudioStopped,
+                              WrapCrossThreadPersistent(this)));
+        }
+      }
+    }
+  }
 }
 
 void BaseAudioContext::PerformCleanupOnMainThread() {
@@ -941,4 +994,18 @@ bool BaseAudioContext::WouldTaintOrigin(const KURL& url) const {
   return true;
 }
 
+void BaseAudioContext::NotifyAudibleAudioStarted() {
+  DCHECK(IsMainThread());
+  // TODO(crbug.com/855069): Actually notify the browser that audible audio has
+  // started.
+  VLOG(1) << this << ": Audible audio started @" << currentTime();
+}
+
+void BaseAudioContext::NotifyAudibleAudioStopped() {
+  DCHECK(IsMainThread());
+  // TODO(crbug.com/855069): Actually notify the browser that audible audio has
+  // started.
+  VLOG(1) << this << ": Audible audio stopped @" << currentTime();
+}
+
 }  // namespace blink

third_party/blink/renderer/modules/webaudio/base_audio_context.h

@@ -245,7 +245,7 @@ class MODULES_EXPORT BaseAudioContext
   void HandlePreRenderTasks(const AudioIOPosition& output_position);
 
   // Called at the end of each render quantum.
-  void HandlePostRenderTasks();
+  void HandlePostRenderTasks(const AudioBus* destination_bus);
 
   DeferredTaskHandler& GetDeferredTaskHandler() const {
     return *deferred_task_handler_;
@@ -452,6 +452,19 @@ class MODULES_EXPORT BaseAudioContext
   // This cannot be nullptr once it is assigned from AudioWorkletThread until
   // the BaseAudioContext goes away.
   WorkerThread* audio_worklet_thread_ = nullptr;
+
+  // Notifies browser when audible audio started or stopped.
+  void NotifyAudibleAudioStarted();
+  void NotifyAudibleAudioStopped();
+
+  // Keeps track if the output of this destination was audible, before the
+  // current rendering quantum.  Used for recording "playback" time.
+  bool was_audible_ = false;
+
+  // Counts the number of render quanta where audible sound was played.  We
+  // determine audibility on render quantum boundaries, so counting quanta is
+  // all that's needed.
+  size_t total_audible_renders_ = 0;
 };
 
 }  // namespace blink

third_party/blink/renderer/modules/webaudio/default_audio_destination_node.cc

@@ -197,7 +197,7 @@ void DefaultAudioDestinationHandler::Render(
   Context()->GetDeferredTaskHandler().ProcessAutomaticPullNodes(
       number_of_frames);
 
-  Context()->HandlePostRenderTasks();
+  Context()->HandlePostRenderTasks(destination_bus);
 
   // Advances the current sample-frame.
   size_t new_sample_frame = current_sample_frame_ + number_of_frames;

third_party/blink/renderer/platform/audio/audio_destination.cc

@@ -150,22 +150,6 @@ void AudioDestination::Render(const WebVector<float*>& destination_data,
                    delay_timestamp, "delay (s)", delay);
 }
 
-// Determine if the rendered data is audible.
-static bool IsAudible(const AudioBus* rendered_data) {
-  // Compute the energy in each channel and sum up the energy in each channel
-  // for the total energy.
-  float energy = 0;
-
-  unsigned data_size = rendered_data->length();
-  for (unsigned k = 0; k < rendered_data->NumberOfChannels(); ++k) {
-    const float* data = rendered_data->Channel(k)->Data();
-    float channel_energy;
-    VectorMath::Vsvesq(data, 1, &channel_energy, data_size);
-    energy += channel_energy;
-  }
-
-  return energy > 0;
-}
 
 void AudioDestination::RequestRender(size_t frames_requested,
                                      size_t frames_to_render,
@@ -204,23 +188,6 @@ void AudioDestination::RequestRender(size_t frames_requested,
     callback_.Render(render_bus_.get(),
                      AudioUtilities::kRenderQuantumFrames, output_position);
 
-    // Detect silence (or not) for MEI
-    bool is_audible = IsAudible(render_bus_.get());
-
-    if (is_audible) {
-      ++total_audible_renders_;
-    }
-
-    if (was_audible_) {
-      if (!is_audible) {
-        was_audible_ = false;
-      }
-    } else {
-      if (is_audible) {
-        was_audible_ = true;
-      }
-    }
-
     fifo_->Push(render_bus_.get());
   }
 

third_party/blink/renderer/platform/audio/audio_destination.h

@@ -138,15 +138,6 @@ class PLATFORM_EXPORT AudioDestination
   // graph into the FIFO.
   scoped_refptr<AudioBus> render_bus_;
 
-  // Keeps track if the output of this destination was audible, before the
-  // current rendering quantum.  Used for recording "playback" time.
-  bool was_audible_ = false;
-
-  // Counts the number of render quanta where audible sound was played.  We
-  // determine audibility on render quantum boundaries, so counting quanta is
-  // all that's needed.
-  size_t total_audible_renders_ = 0;
-
   // Accessed by rendering thread: the render callback function of WebAudio
   // engine. (i.e. DestinationNode)
   AudioIOCallback& callback_;