Bug 1203616 - Properly scale the input buffer of a WaveShaperNode before processing it with the curve. r=karlt, a=sylvestre

--HG--
extra : source : a61652a27e8cc83682b24a9f920df0955b4720b4
extra : amend_source : 6960da7cbae1677685b8af431db301e818d4d4fe

dom/media/webaudio/WaveShaperNode.cpp

@@ -229,26 +229,34 @@ public:
 
     AllocateAudioBlock(channelCount, aOutput);
     for (uint32_t i = 0; i < channelCount; ++i) {
-      float* scaledSample = (float *)(aInput.mChannelData[i]);
-      AudioBlockInPlaceScale(scaledSample, aInput.mVolume);
-      const float* inputBuffer = static_cast<const float*>(scaledSample);
+      const float* inputSamples;
+      float scaledInput[WEBAUDIO_BLOCK_SIZE];
+      if (aInput.mVolume != 1.0f) {
+        AudioBlockCopyChannelWithScale(
+            static_cast<const float*>(aInput.mChannelData[i]),
+                                      aInput.mVolume,
+                                      scaledInput);
+        inputSamples = scaledInput;
+      } else {
+        inputSamples = static_cast<const float*>(aInput.mChannelData[i]);
+      }
       float* outputBuffer = aOutput->ChannelFloatsForWrite(i);
       float* sampleBuffer;
 
       switch (mType) {
       case OverSampleType::None:
         mResampler.Reset(channelCount, aStream->SampleRate(), OverSampleType::None);
-        ProcessCurve<1>(inputBuffer, outputBuffer);
+        ProcessCurve<1>(inputSamples, outputBuffer);
         break;
       case OverSampleType::_2x:
         mResampler.Reset(channelCount, aStream->SampleRate(), OverSampleType::_2x);
-        sampleBuffer = mResampler.UpSample(i, inputBuffer, 2);
+        sampleBuffer = mResampler.UpSample(i, inputSamples, 2);
         ProcessCurve<2>(sampleBuffer, sampleBuffer);
         mResampler.DownSample(i, outputBuffer, 2);
         break;
       case OverSampleType::_4x:
         mResampler.Reset(channelCount, aStream->SampleRate(), OverSampleType::_4x);
-        sampleBuffer = mResampler.UpSample(i, inputBuffer, 4);
+        sampleBuffer = mResampler.UpSample(i, inputSamples, 4);
         ProcessCurve<4>(sampleBuffer, sampleBuffer);
         mResampler.DownSample(i, outputBuffer, 4);
         break;