Avoid reporting 0 as input level when AudioProcessing zero out the audio data

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/threading/thread_checker.h"
 
 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:
   MediaStreamAudioLevelCalculator();
   ~MediaStreamAudioLevelCalculator();
 
   // Calculates the signal level of the audio data.
   // Returns the absolute value of the amplitude of the signal.
   int Calculate(const int16* audio_data, int number_of_channels,
-                int number_of_frames);
+                int number_of_frames, bool has_energy);

[tommi (sloooow) - chröme, 2014/10/17 11:59:08]

can you add documentation for the new parameter?  It's got a very special
purpose so I think it's important to make it clear.

I also think that the name of the parameter is misleading.  In most call sites,
you're passing false now, which will be interpreted as "the input audio data has
no energy" and that's not correct.  I think we should go with something like
force_nonzero_energy or perhaps always_assume_energy.

Btw, just looking at the prototype for this function now, I would wonder why
this flag isn't simply calculated inside the implementation of Calculate since
the audio_data is being passed to the function.  So why the parameter is needed
separate of the data, also needs to be documented.

[no longer working on chromium, 2014/10/20 08:08:42]

All done, please take a look.
Thanks.

 
  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_;
   int max_amplitude_;
   int level_;
 };
 
 }  // namespace content
 
 #endif  // CONTENT_RENDERER_MEDIA_MEDIA_STREAM_AUDIO_LEVEL_CALCULATOR_H_