MediaStream audio sourcing: Bypass audio processing for non-WebRTC cases.

content/renderer/media/media_stream_audio_level_calculator.h

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef CONTENT_RENDERER_MEDIA_MEDIA_STREAM_AUDIO_LEVEL_CALCULATOR_H_
 #define CONTENT_RENDERER_MEDIA_MEDIA_STREAM_AUDIO_LEVEL_CALCULATOR_H_
 
+#include "base/memory/ref_counted.h"
+#include "base/synchronization/lock.h"
 #include "base/threading/thread_checker.h"
 
 namespace media {
 class AudioBus;
 }
 
 namespace content {
 
 // This class is used by the WebRtcLocalAudioTrack to calculate the level of
 // the audio signal. And the audio level will be eventually used by the volume
 // animation UI.
 // The algorithm used by this class is the same as how it is done in
 // third_party/webrtc/voice_engine/level_indicator.cc.
 class MediaStreamAudioLevelCalculator {
  public:
+  // Provides thread-safe access to the current signal level.
+  class ReportedLevel : public base::RefCountedThreadSafe<ReportedLevel> {
+   public:
+    ReportedLevel();
+
+    float Get() const;
+
+   private:
+    friend class base::RefCountedThreadSafe<ReportedLevel>;
+    friend class MediaStreamAudioLevelCalculator;
+
+    ~ReportedLevel();
+
+    mutable base::Lock lock_;
+    float level_;
+  };
+
   MediaStreamAudioLevelCalculator();
   ~MediaStreamAudioLevelCalculator();
 
-  // Calculates the signal level of the audio data, returning the absolute value
-  // of the amplitude of the signal.
-  float Calculate(const media::AudioBus& audio_bus);
+  // Calculates the signal level of the audio data.
+  void Calculate(const media::AudioBus& audio_bus,
+                 bool assume_nonzero_energy);
+
+  // Returns a thread-safe accessor to the current absolute value of the
+  // amplitude of the signal.
+  scoped_refptr<ReportedLevel> reported_level() const {
+    return reported_level_;
+  }
 
  private:
   // Used to DCHECK that the constructor and Calculate() are always called on
   // the same audio thread. Note that the destructor will be called on a
   // different thread, which can be either the main render thread or a new
   // audio thread where WebRtcLocalAudioTrack::OnSetFormat() is called.
   base::ThreadChecker thread_checker_;
 
   int counter_;
   float max_amplitude_;
-  float level_;
+  const scoped_refptr<ReportedLevel> reported_level_;
 };
 
 }  // namespace content
 
 #endif  // CONTENT_RENDERER_MEDIA_MEDIA_STREAM_AUDIO_LEVEL_CALCULATOR_H_