Continue to process AnalyserNode if inputs are silent.

third_party/WebKit/Source/modules/webaudio/AnalyserNode.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 32 matching lines @@
   return adoptRef(new AnalyserHandler(node, sampleRate));
 }
 
 AnalyserHandler::~AnalyserHandler() {
   uninitialize();
 }
 
 void AnalyserHandler::process(size_t framesToProcess) {
   AudioBus* outputBus = output(0).bus();
 
-  if (!isInitialized() || !input(0).isConnected()) {
+  if (!isInitialized()) {
     outputBus->zero();
     return;
   }
 
+  // Must update the internal state even if there are no inputs.

[hongchan, 2017/02/01 01:12:11]

Not sure where this comment should be placed.

[Raymond Toy, 2017/02/01 21:23:47]

Would it help to rephrase it? Or just remove it? (But I think it's important to
say that we need to process the input because line 64 handles the case where
there are no inputs connected.)

[hongchan, 2017/02/03 18:47:40]

The comment is not really relevant to what's happening at l.59. Isn't it? That
means this will confuse us when we come back later.

[Raymond Toy, 2017/02/03 18:50:00]

How about:

// Must always update internal state with any inputs.

   AudioBus* inputBus = input(0).bus();
 
   // Give the analyser the audio which is passing through this AudioNode.
   m_analyser.writeInput(inputBus, framesToProcess);
 
+  if (!input(0).isConnected()) {
+    // No inputs, so clear the output, and propagate the silence hint.
+    outputBus->zero();
+    return;
+  }
+
   // For in-place processing, our override of pullInputs() will just pass the
   // audio data through unchanged if the channel count matches from input to
   // output (resulting in inputBus == outputBus). Otherwise, do an up-mix to
   // stereo.
   if (inputBus != outputBus)
     outputBus->copyFrom(*inputBus);
 }
 
 void AnalyserHandler::setFftSize(unsigned size,
                                  ExceptionState& exceptionState) {
@@ skipping 162 matching lines @@
 
 void AnalyserNode::getFloatTimeDomainData(DOMFloat32Array* array) {
   analyserHandler().getFloatTimeDomainData(array);
 }
 
 void AnalyserNode::getByteTimeDomainData(DOMUint8Array* array) {
   analyserHandler().getByteTimeDomainData(array);
 }
 
 }  // namespace blink