Merge 143565

Source/WebCore/Modules/webaudio/ChannelMergerNode.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
@@ skipping 18 matching lines @@
 #include "config.h"
 
 #if ENABLE(WEB_AUDIO)
 
 #include "ChannelMergerNode.h"
 
 #include "AudioContext.h"
 #include "AudioNodeInput.h"
 #include "AudioNodeOutput.h"
 
+const unsigned DefaultNumberOfOutputChannels = 1;
+
 namespace WebCore {
 
 PassRefPtr<ChannelMergerNode> ChannelMergerNode::create(AudioContext* context, float sampleRate, unsigned numberOfInputs)
 {
     if (!numberOfInputs || numberOfInputs > AudioContext::maxNumberOfChannels())
         return 0;
     
     return adoptRef(new ChannelMergerNode(context, sampleRate, numberOfInputs));      
 }
 
 ChannelMergerNode::ChannelMergerNode(AudioContext* context, float sampleRate, unsigned numberOfInputs)
     : AudioNode(context, sampleRate)
+    , m_desiredNumberOfOutputChannels(DefaultNumberOfOutputChannels)
 {
     // Create the requested number of inputs.
     for (unsigned i = 0; i < numberOfInputs; ++i)
         addInput(adoptPtr(new AudioNodeInput(this)));
 
     addOutput(adoptPtr(new AudioNodeOutput(this, 1)));
     
     setNodeType(NodeTypeChannelMerger);
     
     initialize();
 }
 
 void ChannelMergerNode::process(size_t framesToProcess)
 {
     AudioNodeOutput* output = this->output(0);
     ASSERT(output);
-    ASSERT_UNUSED(framesToProcess, framesToProcess == output->bus()->length());    
+    ASSERT_UNUSED(framesToProcess, framesToProcess == output->bus()->length());
+
+    // Output bus not updated yet, so just output silence.
+    if (m_desiredNumberOfOutputChannels != output->numberOfChannels()) {
+        output->bus()->zero();
+        return;
+    }
     
     // Merge all the channels from all the inputs into one output.
     unsigned outputChannelIndex = 0;
     for (unsigned i = 0; i < numberOfInputs(); ++i) {
         AudioNodeInput* input = this->input(i);
         if (input->isConnected()) {
             unsigned numberOfInputChannels = input->bus()->numberOfChannels();
             
             // Merge channels from this particular input.
             for (unsigned j = 0; j < numberOfInputChannels; ++j) {
@@ skipping 24 matching lines @@
     for (unsigned i = 0; i < numberOfInputs(); ++i) {
         AudioNodeInput* input = this->input(i);
         if (input->isConnected())
             numberOfOutputChannels += input->bus()->numberOfChannels();
     }
 
     // Set the correct number of channels on the output
     AudioNodeOutput* output = this->output(0);
     ASSERT(output);
     output->setNumberOfChannels(numberOfOutputChannels);
+    // There can in rare cases be a slight delay before the output bus is updated to the new number of
+    // channels because of tryLocks() in the context's updating system. So record the new number of
+    // output channels here.
+    m_desiredNumberOfOutputChannels = numberOfOutputChannels;
 
     AudioNode::checkNumberOfChannelsForInput(input);
 }
 
 } // namespace WebCore
 
 #endif // ENABLE(WEB_AUDIO)