Adds volume level measurements to the AudioInputController for low-latency clients

media/audio/audio_power_monitor.h

 // Copyright 2013 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 MEDIA_AUDIO_AUDIO_POWER_MONITOR_H_
 #define MEDIA_AUDIO_AUDIO_POWER_MONITOR_H_
 
 #include <limits>
 #include <utility>
 
 #include "base/callback.h"
 #include "base/synchronization/lock.h"
+#include "media/audio/audio_parameters.h"
 #include "media/base/media_export.h"
 
 // An audio signal power monitor.  It is periodically provided an AudioBus by
 // the native audio thread, and the audio samples in each channel are analyzed
 // to determine the average power of the signal over a time period.  Here
 // "average power" is a running average calculated by using a first-order
 // low-pass filter over the square of the samples scanned.  Whenever reporting
 // the power level, this running average is converted to dBFS (decibels relative
 // to full-scale) units.
 //
@@ skipping 10 matching lines @@
 
 class AudioBus;
 
 class MEDIA_EXPORT AudioPowerMonitor {
  public:
   // |sample_rate| is the audio signal sample rate (Hz).  |time_constant|
   // characterizes how samples are averaged over time to determine the power
   // level; and is the amount of time it takes a zero power level to increase to
   // ~63.2% of maximum given a step input signal.
   AudioPowerMonitor(int sample_rate, const base::TimeDelta& time_constant);
+  AudioPowerMonitor(const AudioParameters& params);
 
   ~AudioPowerMonitor();
 
   // Reset power monitor to initial state (zero power level).  This should not
   // be called while another thread is scanning.
   void Reset();
 
   // Scan more |frames| of audio data from |buffer|.  It is safe to call this
   // from a real-time priority thread.
   void Scan(const AudioBus& buffer, int frames);
+  void Scan(const void* data, uint32 size);
 
   // Returns the current power level in dBFS and clip status.  Clip status is
   // true whenever any *one* sample scanned exceeded maximum amplitude since
   // this method's last invocation.  It is safe to call this method from any
   // thread.
   std::pair<float, bool> ReadCurrentPowerAndClip();
 
   // dBFS value corresponding to zero power in the audio signal.
   static float zero_power() { return -std::numeric_limits<float>::infinity(); }
 
   // dBFS value corresponding to maximum power in the audio signal.
   static float max_power() { return 0.0f; }
 
  private:
   // The weight applied when averaging-in each sample.  Computed from the
   // |sample_rate| and |time_constant|.
   const float sample_weight_;
 
   // Accumulated results over one or more calls to Scan().  These should only be
   // touched by the thread invoking Scan().
   float average_power_;
   bool has_clipped_;
 
   // Copies of power and clip status, used to deliver results synchronously
   // across threads.
   base::Lock reading_lock_;
   float power_reading_;
   bool clipped_reading_;
 
+  scoped_ptr<AudioBus> audio_bus_;
+  AudioParameters params_;
+
   DISALLOW_COPY_AND_ASSIGN(AudioPowerMonitor);
 };
 
 }  // namespace media
 
 #endif  // MEDIA_AUDIO_AUDIO_POWER_MONITOR_H_