Bug 881959 - Mute WebAudio nodes that are part of a cycle that contains no DelayNode, and make cycles work. r=ehsan

--HG--
extra : rebase_source : d4bc378128cf15f8d8395b45b4443ca6b06c5bd2

content/media/AudioNodeEngine.h

@@ -15,6 +15,7 @@ namespace mozilla {
 namespace dom {
 struct ThreeDPoint;
 class AudioParamTimeline;
+class DelayNodeEngine;
 }
 
 class AudioNodeStream;
@@ -206,6 +207,8 @@ public:
     MOZ_COUNT_DTOR(AudioNodeEngine);
   }
 
+  virtual dom::DelayNodeEngine* AsDelayNodeEngine() { return nullptr; }
+
   virtual void SetStreamTimeParameter(uint32_t aIndex, TrackTicks aParam)
   {
     NS_ERROR("Invalid SetStreamTimeParameter index");

content/media/AudioNodeStream.cpp

@@ -286,6 +286,20 @@ AudioNodeStream::ObtainInputBlock(AudioChunk& aTmpChunk, uint32_t aPortIndex)
         a->IsAudioParamStream()) {
       continue;
     }
+
+    // It is possible for mLastChunks to be empty here, because `a` might be a
+    // AudioNodeStream that has not been scheduled yet, because it is further
+    // down the graph _but_ as a connection to this node. Because we enforce the
+    // presence of at least one DelayNode, with at least one block of delay, and
+    // because the output of a DelayNode when it has been fed less that
+    // `delayTime` amount of audio is silence, we can simply continue here,
+    // because this input would not influence the output of this node. Next
+    // iteration, a->mLastChunks.IsEmpty() will be false, and everthing will
+    // work as usual.
+    if (a->mLastChunks.IsEmpty()) {
+      continue;
+    }
+
     AudioChunk* chunk = &a->mLastChunks[mInputs[i]->OutputNumber()];
     MOZ_ASSERT(chunk);
     if (chunk->IsNull() || chunk->mChannelData.IsEmpty()) {
@@ -412,8 +426,7 @@ AudioNodeStream::ProduceOutput(GraphTime aFrom, GraphTime aTo)
   uint16_t outputCount = std::max(uint16_t(1), mEngine->OutputCount());
   mLastChunks.SetLength(outputCount);
 
-  if (mInCycle) {
-    // XXX DelayNode not supported yet so just produce silence
+  if (mMuted) {
     for (uint16_t i = 0; i < outputCount; ++i) {
       mLastChunks[i].SetNull(WEBAUDIO_BLOCK_SIZE);
     }

content/media/AudioNodeStream.h

@@ -21,6 +21,7 @@ namespace mozilla {
 namespace dom {
 struct ThreeDPoint;
 class AudioParamTimeline;
+class DelayNodeEngine;
 }
 
 class ThreadSharedFloatArrayBufferList;
@@ -54,7 +55,8 @@ public:
       mKind(aKind),
       mNumberOfInputChannels(2),
       mMarkAsFinishedAfterThisBlock(false),
-      mAudioParamStream(false)
+      mAudioParamStream(false),
+      mMuted(false)
   {
     MOZ_ASSERT(NS_IsMainThread());
     mChannelCountMode = dom::ChannelCountMode::Max;
@@ -103,6 +105,14 @@ public:
   {
     return mAudioParamStream;
   }
+  void Mute() {
+    mMuted = true;
+  }
+
+  void Unmute() {
+    mMuted = false;
+  }
+
   const OutputChunks& LastChunks() const
   {
     return mLastChunks;
@@ -153,6 +163,8 @@ protected:
   bool mMarkAsFinishedAfterThisBlock;
   // Whether the stream is an AudioParamHelper stream.
   bool mAudioParamStream;
+  // Whether the stream is muted. Access only on the MediaStreamGraph thread.
+  bool mMuted;
 };
 
 }

content/media/MediaStreamGraph.cpp

@@ -472,12 +472,32 @@ MediaStreamGraphImpl::UpdateStreamOrderForStream(mozilla::LinkedList<MediaStream
   NS_ASSERTION(!stream->mHasBeenOrdered, "stream should not have already been ordered");
   if (stream->mIsOnOrderingStack) {
     MediaStream* iter = aStack->getLast();
+    AudioNodeStream* ns = stream->AsAudioNodeStream();
+    bool delayNodePresent = ns ? ns->Engine()->AsDelayNodeEngine() != nullptr : false;
+    bool cycleFound = false;
     if (iter) {
       do {
+        cycleFound = true;
         iter->AsProcessedStream()->mInCycle = true;
+        AudioNodeStream* ns = iter->AsAudioNodeStream();
+        if (ns && ns->Engine()->AsDelayNodeEngine()) {
+          delayNodePresent = true;
+        }
         iter = iter->getPrevious();
       } while (iter && iter != stream);
     }
+    if (cycleFound && !delayNodePresent) {
+      // If we have detected a cycle, the previous loop should exit with stream
+      // == iter. Go back in the cycle and mute all nodes we find.
+      MOZ_ASSERT(iter);
+      do {
+        // There can't be non-AudioNodeStream here, MediaStreamAudio{Source,
+        // Destination}Node are connected to regular MediaStreams, but they can't be
+        // in a cycle (there is no content API to do so).
+        MOZ_ASSERT(iter->AsAudioNodeStream());
+        iter->AsAudioNodeStream()->Mute();
+      } while((iter = iter->getNext()));
+    }
     return;
   }
   ProcessedMediaStream* ps = stream->AsProcessedStream();
@@ -513,6 +533,10 @@ MediaStreamGraphImpl::UpdateStreamOrder()
     ProcessedMediaStream* ps = stream->AsProcessedStream();
     if (ps) {
       ps->mInCycle = false;
+      AudioNodeStream* ns = ps->AsAudioNodeStream();
+      if (ns) {
+        ns->Unmute();
+      }
     }
   }
 

content/media/webaudio/AudioNode.h

@@ -130,6 +130,10 @@ public:
     return nullptr;
   }
 
+  virtual const DelayNode* AsDelayNode() const {
+    return nullptr;
+  }
+
   AudioContext* GetParentObject() const
   {
     return mContext;

content/media/webaudio/DelayNode.cpp

@@ -44,6 +44,11 @@ public:
   {
   }
 
+  virtual DelayNodeEngine* AsDelayNodeEngine()
+  {
+    return this;
+  }
+
   void SetSourceStream(AudioNodeStream* aSource)
   {
     mSource = aSource;

content/media/webaudio/DelayNode.h

@@ -32,6 +32,11 @@ public:
     return mDelay;
   }
 
+  virtual const DelayNode* AsDelayNode() const MOZ_OVERRIDE
+  {
+    return this;
+  }
+
   virtual void NotifyInputConnected() MOZ_OVERRIDE
   {
     mMediaStreamGraphUpdateIndexAtLastInputConnection =