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

NOTRY=true
BUG=357566

Review URL: https://codereview.chromium.org/216773003

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@260212 0039d316-1c4b-4281-b951-d872f2087c98

content/renderer/media/media_stream_audio_level_calculator.cc

@@ -42,12 +42,6 @@ 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] =
-      {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;
@@ -56,18 +50,7 @@ int MediaStreamAudioLevelCalculator::Calculate(const int16* audio_data,
   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;

content/renderer/media/media_stream_audio_level_calculator.h

@@ -20,8 +20,7 @@ class MediaStreamAudioLevelCalculator {
   ~MediaStreamAudioLevelCalculator();
 
   // Calculates the signal level of the audio data.
-  // Returns the level of bars that the volume animation UI uses for
-  // presenting the energy 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);