Add a noise indicator to the speech bubble volume indicator.

content/browser/speech/endpointer/energy_endpointer.cc

 // Copyright (c) 2010 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.
 //
 // To know more about the algorithm used and the original code which this is
 // based of, see
 // https://wiki.corp.google.com/twiki/bin/view/Main/ChromeGoogleCodeXRef
 
 #include "content/browser/speech/endpointer/energy_endpointer.h"
 
@@ skipping 15 matching lines @@
   double sum = static_cast<double>(sum_int64);
   sum /= num_samples;
   double ssq = static_cast<double>(ssq_int64);
   return static_cast<float>(sqrt((ssq / num_samples) - (sum * sum)));
 }
 
 int64 Secs2Usecs(float seconds) {
   return static_cast<int64>(0.5 + (1.0e6 * seconds));
 }
 
+float GetDecibel(float value) {
+  const float kVerySmallValue = 1.0e-100f;
+  if (value < kVerySmallValue)
+    value = kVerySmallValue;
+  return 20 * log10(value);
+}
+
 }  // namespace
 
 namespace speech_input {
 
 // Stores threshold-crossing histories for making decisions about the speech
 // state.
 class EnergyEndpointer::HistoryRing {
  public:
   HistoryRing() : insertion_index_(0) {}
 
@@ skipping 273 matching lines @@
 
     // Set a floor
     if (decision_threshold_ < params_.min_decision_threshold())
       decision_threshold_ = params_.min_decision_threshold();
   }
 
   // Update speech and noise levels.
   UpdateLevels(rms);
   ++frame_counter_;
 
-  if (rms_out) {
-    *rms_out = -120.0;
-    if ((noise_level_ > 0.0) && ((rms / noise_level_ ) > 0.000001))
-      *rms_out = static_cast<float>(20.0 * log10(rms / noise_level_));
-  }
+  if (rms_out)
+    *rms_out = GetDecibel(rms);
+}
+
+float EnergyEndpointer::GetNoiseLevelDb() const {
+  return GetDecibel(noise_level_);
 }
 
 void EnergyEndpointer::UpdateLevels(float rms) {
   // Update quickly initially. We assume this is noise and that
   // speech is 6dB above the noise.
   if (frame_counter_ < fast_update_frames_) {
     // Alpha increases from 0 to (k-1)/k where k is the number of time
     // steps in the initial adaptation period.
     float alpha = static_cast<float>(frame_counter_) /
         static_cast<float>(fast_update_frames_);
@@ skipping 16 matching lines @@
       decision_threshold_ = params_.min_decision_threshold();
   }
 }
 
 EpStatus EnergyEndpointer::Status(int64* status_time)  const {
   *status_time = history_->EndTime();
   return status_;
 }
 
 }  // namespace speech