Use the absolute magnitude instead of the bar level as the level of the input signal

content/renderer/media/media_stream_audio_level_calculator.cc

 // 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.
 
 #include "content/renderer/media/media_stream_audio_level_calculator.h"
 
 #include "base/logging.h"
 #include "base/stl_util.h"
 
 namespace content {
@@ skipping 24 matching lines @@
       level_(0) {
 }
 
 MediaStreamAudioLevelCalculator::~MediaStreamAudioLevelCalculator() {
 }
 
 int MediaStreamAudioLevelCalculator::Calculate(const int16* audio_data,
                                                int number_of_channels,
                                                int number_of_frames) {
   DCHECK(thread_checker_.CalledOnValidThread());
-  // Permutation of bars that reprents the amplitude level of the audio signal.
-  // The number of elements is 33 because we are indexing them in the range of
-  // [0, 32].
-  static const int kPermutation[33] =

[no longer working on chromium, 2014/03/28 10:30:34]

Tommi, it turns out that libjingle uses _currentLevelFullRange as the input
level:
https://code.google.com/p/chromium/codesearch#chromium/src/third_party/webrtc...

I am also removing this permutation code since it is not used and just
confusing.

[tommi (sloooow) - chröme, 2014/03/28 11:57:02]

great :)

-      {0,1,2,3,4,4,5,5,5,5,6,6,6,6,6,7,7,7,7,8,8,8,9,9,9,9,9,9,9,9,9,9,9};
-
   // |level_| is updated every 10 callbacks. For the case where callback comes
   // every 10ms, |level_| will be updated approximately every 100ms.
   static const int kUpdateFrequency = 10;
 
   int max = MaxAmplitude(audio_data, number_of_channels * number_of_frames);
   max_amplitude_ = std::max(max_amplitude_, max);
 
   if (counter_++ == kUpdateFrequency) {
-    // Divide the max amplitude (32768) by 1000 to get in the range of [0,32]
-    // which is the range of the permutation array.
-    int index = static_cast<int>(max_amplitude_ / 1000);
-
-    // Make it less likely that the bar stays at position 0. I.e. only if
-    // its in the range 0-250 (instead of 0-1000)
-    if (index == 0 && max_amplitude_ > 250)
-      index = 1;
-
-    // |level_| will be the value in the permutation array that the |index| is
-    // pointing to.
-    level_ = kPermutation[index];
+    level_ = max_amplitude_;
 
     // Decay the absolute maximum amplitude by 1/4.
     max_amplitude_ >>= 2;
 
     // Reset the counter.
     counter_ = 0;
   }
 
   return level_;
 }
 
 }  // namespace content