Bug 1424906 - Fix PeriodicWave disableNormalization false behaviour; r=padenot

This adds a scaling factor of 0.5 even when normalization is
disabled, which is required for correct results.

MozReview-Commit-ID: J0VbMcaacGc

--HG--
extra : rebase_source : 1a8e2dd21a6a48a02fbafda994e42b59c5761ea4

dom/media/webaudio/blink/PeriodicWave.cpp

@@ -274,7 +274,11 @@ void PeriodicWave::createBandLimitedTables(float fundamentalFrequency,
 
     // For the first range (which has the highest power), calculate
     // its peak value then compute normalization scale.
-    if (!m_disableNormalization && !rangeIndex) {
+    if (m_disableNormalization) {
+      // See Bug 1424906, results need to be scaled by 0.5 even
+      // when normalization is disabled.
+      m_normalizationScale = 0.5;
+    } else if (!rangeIndex) {
         float maxValue;
         maxValue = AudioBufferPeakValue(data, m_periodicWaveSize);
 
@@ -283,9 +287,7 @@ void PeriodicWave::createBandLimitedTables(float fundamentalFrequency,
     }
 
     // Apply normalization scale.
-    if (!m_disableNormalization) {
-      AudioBufferInPlaceScale(data, m_normalizationScale, m_periodicWaveSize);
-    }
+    AudioBufferInPlaceScale(data, m_normalizationScale, m_periodicWaveSize);
 }
 
 void PeriodicWave::generateBasicWaveform(OscillatorType shape)

dom/media/webaudio/test/test_periodicWaveDisableNormalization.html

@@ -81,9 +81,7 @@ var gTest = {
 
       buffer.getChannelData(1)[i] = buffer.getChannelData(0)[i];
 
-      // TODO: We need to scale by a factor of two to make the results work
-      //       out here. This seems suspicious, see Bug 1266737.
-      buffer.getChannelData(2)[i] = 2.0 *
+      buffer.getChannelData(2)[i] =
         (real[1] * Math.cos(2 * Math.PI * realFundamental * i /
                             context.sampleRate) +
          real[realMax] * Math.cos(2 * Math.PI * realMax * realFundamental * i /