Don't clip FFT output values to minDecibels.

third_party/WebKit/Source/modules/webaudio/RealtimeAnalyser.cpp

 /*
  * Copyright (C) 2010, Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1.  Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2.  Redistributions in binary form must reproduce the above copyright
  *    notice, this list of conditions and the following disclaimer in the
@@ skipping 174 matching lines @@
 }
 
 void RealtimeAnalyser::getFloatFrequencyData(DOMFloat32Array* destinationArray)
 {
     ASSERT(isMainThread());
     ASSERT(destinationArray);
 
     doFFTAnalysis();
 
     // Convert from linear magnitude to floating-point decibels.
-    const double minDecibels = m_minDecibels;
     unsigned sourceLength = magnitudeBuffer().size();
     size_t len = std::min(sourceLength, destinationArray->length());
     if (len > 0) {
         const float* source = magnitudeBuffer().data();
         float* destination = destinationArray->data();
 
         for (unsigned i = 0; i < len; ++i) {
             float linearValue = source[i];
-            double dbMag = !linearValue ? minDecibels : AudioUtilities::linearToDecibels(linearValue);
+            double dbMag = AudioUtilities::linearToDecibels(linearValue);
             destination[i] = float(dbMag);
         }
     }
 }
 
 void RealtimeAnalyser::getByteFrequencyData(DOMUint8Array* destinationArray)
 {
     ASSERT(isMainThread());
     ASSERT(destinationArray);
 
     doFFTAnalysis();
 
     // Convert from linear magnitude to unsigned-byte decibels.
     unsigned sourceLength = magnitudeBuffer().size();
     size_t len = std::min(sourceLength, destinationArray->length());
     if (len > 0) {
         const double rangeScaleFactor = m_maxDecibels == m_minDecibels ? 1 : 1 / (m_maxDecibels - m_minDecibels);
         const double minDecibels = m_minDecibels;
 
         const float* source = magnitudeBuffer().data();
         unsigned char* destination = destinationArray->data();
 
         for (unsigned i = 0; i < len; ++i) {
             float linearValue = source[i];
-            double dbMag = !linearValue ? minDecibels : AudioUtilities::linearToDecibels(linearValue);
+            double dbMag = AudioUtilities::linearToDecibels(linearValue);
 
             // The range m_minDecibels to m_maxDecibels will be scaled to byte values from 0 to UCHAR_MAX.
             double scaledValue = UCHAR_MAX * (dbMag - minDecibels) * rangeScaleFactor;
 
             // Clip to valid range.
             if (scaledValue < 0)
                 scaledValue = 0;
             if (scaledValue > UCHAR_MAX)
                 scaledValue = UCHAR_MAX;
 
@@ skipping 60 matching lines @@
             if (scaledValue > UCHAR_MAX)
                 scaledValue = UCHAR_MAX;
 
             destination[i] = static_cast<unsigned char>(scaledValue);
         }
     }
 }
 
 } // namespace blink