content/renderer/media/media_stream_audio_level_calculator.h

   1 // Copyright 2014 The Chromium Authors. All rights reserved.
   2 // Use of this source code is governed by a BSD-style license that can be
   3 // found in the LICENSE file.
   4
   5 #ifndef CONTENT_RENDERER_MEDIA_MEDIA_STREAM_AUDIO_LEVEL_CALCULATOR_H_
   6 #define CONTENT_RENDERER_MEDIA_MEDIA_STREAM_AUDIO_LEVEL_CALCULATOR_H_
   7
   8 #include "base/threading/thread_checker.h"
   9
  10 namespace media {
  11 class AudioBus;
  12 }
  13
  14 namespace content {
  15
  16 // This class is used by the WebRtcLocalAudioTrack to calculate the level of
  17 // the audio signal. And the audio level will be eventually used by the volume
  18 // animation UI.
  19 // The algorithm used by this class is the same as how it is done in
  20 // third_party/webrtc/voice_engine/level_indicator.cc.
  21 class MediaStreamAudioLevelCalculator {
  22  public:
  23   MediaStreamAudioLevelCalculator();
  24   ~MediaStreamAudioLevelCalculator();
  25
  26   // Calculates the signal level of the audio data, returning the absolute value
  27   // of the amplitude of the signal.
  28   float Calculate(const media::AudioBus& audio_bus);
  29
  30  private:
  31   // Used to DCHECK that the constructor and Calculate() are always called on
  32   // the same audio thread. Note that the destructor will be called on a
  33   // different thread, which can be either the main render thread or a new
  34   // audio thread where WebRtcLocalAudioTrack::OnSetFormat() is called.
  35   base::ThreadChecker thread_checker_;
  36
  37   int counter_;
  38   float max_amplitude_;
  39   float level_;
  40 };
  41
  42 }  // namespace content
  43
  44 #endif  // CONTENT_RENDERER_MEDIA_MEDIA_STREAM_AUDIO_LEVEL_CALCULATOR_H_