diff --git a/dom/media/DecodedStream.cpp b/dom/media/DecodedStream.cpp
index e7c98486218..8eff602a620 100644
--- a/dom/media/DecodedStream.cpp
+++ b/dom/media/DecodedStream.cpp
@@ -193,8 +193,8 @@ OutputStreamData::Init(DecodedStream* aDecodedStream, ProcessedMediaStream* aStr
   aStream->AddListener(mListener);
 }
 
-DecodedStream::DecodedStream(ReentrantMonitor& aMonitor)
-  : mMonitor(aMonitor)
+DecodedStream::DecodedStream()
+  : mMonitor("DecodedStream::mMonitor")
 {
   //
 }
@@ -202,7 +202,7 @@ DecodedStream::DecodedStream(ReentrantMonitor& aMonitor)
 DecodedStreamData*
 DecodedStream::GetData() const
 {
-  GetReentrantMonitor().AssertCurrentThreadIn();
+  ReentrantMonitorAutoEnter mon(GetReentrantMonitor());
   return mData.get();
 }
 
@@ -210,7 +210,7 @@ void
 DecodedStream::DestroyData()
 {
   MOZ_ASSERT(NS_IsMainThread());
-  GetReentrantMonitor().AssertCurrentThreadIn();
+  ReentrantMonitorAutoEnter mon(GetReentrantMonitor());
 
   // Avoid the redundant blocking to output stream.
   if (!mData) {
@@ -245,7 +245,7 @@ void
 DecodedStream::RecreateData(MediaStreamGraph* aGraph)
 {
   MOZ_ASSERT(NS_IsMainThread());
-  GetReentrantMonitor().AssertCurrentThreadIn();
+  ReentrantMonitorAutoEnter mon(GetReentrantMonitor());
   MOZ_ASSERT((aGraph && !mData && OutputStreams().IsEmpty()) || // first time
              (!aGraph && mData)); // 2nd time and later
 
@@ -300,7 +300,7 @@ void
 DecodedStream::Connect(ProcessedMediaStream* aStream, bool aFinishWhenEnded)
 {
   MOZ_ASSERT(NS_IsMainThread());
-  GetReentrantMonitor().AssertCurrentThreadIn();
+  ReentrantMonitorAutoEnter mon(GetReentrantMonitor());
 
   OutputStreamData* os = OutputStreams().AppendElement();
   os->Init(this, aStream);
@@ -314,7 +314,7 @@ DecodedStream::Connect(ProcessedMediaStream* aStream, bool aFinishWhenEnded)
 void
 DecodedStream::SetPlaying(bool aPlaying)
 {
-  GetReentrantMonitor().AssertCurrentThreadIn();
+  ReentrantMonitorAutoEnter mon(GetReentrantMonitor());
   MOZ_ASSERT(mData);
   mData->SetPlaying(aPlaying);
 }
diff --git a/dom/media/DecodedStream.h b/dom/media/DecodedStream.h
index 748576c9826..4117dd1cff4 100644
--- a/dom/media/DecodedStream.h
+++ b/dom/media/DecodedStream.h
@@ -85,7 +85,7 @@ public:
 
 class DecodedStream {
 public:
-  explicit DecodedStream(ReentrantMonitor& aMonitor);
+  DecodedStream();
   DecodedStreamData* GetData() const;
   void DestroyData();
   void RecreateData(MediaStreamGraph* aGraph);
@@ -100,7 +100,15 @@ private:
   UniquePtr<DecodedStreamData> mData;
   // Data about MediaStreams that are being fed by the decoder.
   nsTArray<OutputStreamData> mOutputStreams;
-  ReentrantMonitor& mMonitor;
+
+  // TODO: This is a temp solution to get rid of decoder monitor on the main
+  // thread in MDSM::AddOutputStream and MDSM::RecreateDecodedStream as
+  // required by bug 1146482. DecodedStream needs to release monitor before
+  // calling back into MDSM functions in order to prevent deadlocks.
+  //
+  // Please move all capture-stream related code from MDSM into DecodedStream
+  // and apply "dispatch + mirroring" to get rid of this monitor in the future.
+  mutable ReentrantMonitor mMonitor;
 };
 
 } // namespace mozilla
diff --git a/dom/media/MediaDecoderStateMachine.cpp b/dom/media/MediaDecoderStateMachine.cpp
index bea799ab3aa..3106cd47735 100644
--- a/dom/media/MediaDecoderStateMachine.cpp
+++ b/dom/media/MediaDecoderStateMachine.cpp
@@ -237,8 +237,7 @@ MediaDecoderStateMachine::MediaDecoderStateMachine(MediaDecoder* aDecoder,
   mDecodingFrozenAtStateDecoding(false),
   mSentLoadedMetadataEvent(false),
   mSentFirstFrameLoadedEvent(false),
-  mSentPlaybackEndedEvent(false),
-  mDecodedStream(mDecoder->GetReentrantMonitor())
+  mSentPlaybackEndedEvent(false)
 {
   MOZ_COUNT_CTOR(MediaDecoderStateMachine);
   NS_ASSERTION(NS_IsMainThread(), "Should be on main thread.");
@@ -3348,7 +3347,6 @@ uint32_t MediaDecoderStateMachine::GetAmpleVideoFrames() const
 
 DecodedStreamData* MediaDecoderStateMachine::GetDecodedStream() const
 {
-  AssertCurrentThreadInMonitor();
   return mDecodedStream.GetData();
 }
 
@@ -3382,7 +3380,6 @@ void MediaDecoderStateMachine::AddOutputStream(ProcessedMediaStream* aStream,
   MOZ_ASSERT(NS_IsMainThread());
   DECODER_LOG("AddOutputStream aStream=%p!", aStream);
 
-  ReentrantMonitorAutoEnter mon(mDecoder->GetReentrantMonitor());
   if (!GetDecodedStream()) {
     RecreateDecodedStream(aStream->Graph());
   }
@@ -3393,9 +3390,15 @@ void MediaDecoderStateMachine::AddOutputStream(ProcessedMediaStream* aStream,
 void MediaDecoderStateMachine::RecreateDecodedStream(MediaStreamGraph* aGraph)
 {
   MOZ_ASSERT(NS_IsMainThread());
-  ReentrantMonitorAutoEnter mon(mDecoder->GetReentrantMonitor());
   mDecodedStream.RecreateData(aGraph);
-  mDecodedStream.SetPlaying(IsPlaying());
+
+  nsRefPtr<MediaDecoderStateMachine> self = this;
+  nsCOMPtr<nsIRunnable> r = NS_NewRunnableFunction([self] () -> void
+  {
+    ReentrantMonitorAutoEnter mon(self->mDecoder->GetReentrantMonitor());
+    self->mDecodedStream.SetPlaying(self->IsPlaying());
+  });
+  TaskQueue()->Dispatch(r.forget());
 }
 
 } // namespace mozilla