Bug 1190676 - Part 3 - Make getting a MediaStreamGraph for a channel more explicit. r=roc

Hopefully this wil also prevent getting the wrong graph.

--HG--
extra : rebase_source : 3465c29807798d237c4d289b1a88845684373de5

dom/media/MediaStreamGraph.cpp

@@ -58,7 +58,7 @@ PRLogModuleInfo* gMediaStreamGraphLog;
 #endif
 
 /**
- * The singleton graph instance.
+ * A hash table containing the graph instances, one per AudioChannel.
  */
 static nsDataHashtable<nsUint32HashKey, MediaStreamGraphImpl*> gGraphs;
 
@@ -2865,9 +2865,8 @@ ProcessedMediaStream::DestroyImpl()
   // SetStreamOrderDirty(), for other reasons.
 }
 
-MediaStreamGraphImpl::MediaStreamGraphImpl(bool aRealtime,
+MediaStreamGraphImpl::MediaStreamGraphImpl(GraphDriverType aDriverRequested,
                                            TrackRate aSampleRate,
-                                           bool aStartWithAudioDriver,
                                            dom::AudioChannel aChannel)
   : MediaStreamGraph(aSampleRate)
   , mPortCount(0)
@@ -2882,7 +2881,7 @@ MediaStreamGraphImpl::MediaStreamGraphImpl(bool aRealtime,
   , mFlushSourcesOnNextIteration(false)
   , mDetectedNotRunning(false)
   , mPostedRunInStableState(false)
-  , mRealtime(aRealtime)
+  , mRealtime(aDriverRequested != OFFLINE_THREAD_DRIVER)
   , mNonRealtimeProcessing(false)
   , mStreamOrderDirty(false)
   , mLatencyLog(AsyncLatencyLogger::Get())
@@ -2903,7 +2902,7 @@ MediaStreamGraphImpl::MediaStreamGraphImpl(bool aRealtime,
   }
 
   if (mRealtime) {
-    if (aStartWithAudioDriver) {
+    if (aDriverRequested == AUDIO_THREAD_DRIVER) {
       AudioCallbackDriver* driver = new AudioCallbackDriver(this, aChannel);
       mDriver = driver;
       mMixer.AddCallback(driver);
@@ -2960,7 +2959,7 @@ MediaStreamGraphShutdownObserver::Observe(nsISupports *aSubject,
 }
 
 MediaStreamGraph*
-MediaStreamGraph::GetInstance(bool aStartWithAudioDriver,
+MediaStreamGraph::GetInstance(MediaStreamGraph::GraphDriverType aGraphDriverRequested,
                               dom::AudioChannel aChannel)
 {
   NS_ASSERTION(NS_IsMainThread(), "Main thread only");
@@ -2976,10 +2975,15 @@ MediaStreamGraph::GetInstance(bool aStartWithAudioDriver,
 
     CubebUtils::InitPreferredSampleRate();
 
-    graph = new MediaStreamGraphImpl(true, CubebUtils::PreferredSampleRate(), aStartWithAudioDriver, aChannel);
+    graph = new MediaStreamGraphImpl(aGraphDriverRequested,
+                                     CubebUtils::PreferredSampleRate(),
+                                     aChannel);
+
     gGraphs.Put(channel, graph);
 
-    STREAM_LOG(LogLevel::Debug, ("Starting up MediaStreamGraph %p", graph));
+    STREAM_LOG(LogLevel::Debug,
+        ("Starting up MediaStreamGraph %p for channel %s",
+         graph, AudioChannelValues::strings[channel]));
   }
 
   return graph;
@@ -2990,7 +2994,10 @@ MediaStreamGraph::CreateNonRealtimeInstance(TrackRate aSampleRate)
 {
   NS_ASSERTION(NS_IsMainThread(), "Main thread only");
 
-  MediaStreamGraphImpl* graph = new MediaStreamGraphImpl(false, aSampleRate);
+  MediaStreamGraphImpl* graph =
+    new MediaStreamGraphImpl(OFFLINE_THREAD_DRIVER,
+                             aSampleRate,
+                             AudioChannel::Normal);
 
   STREAM_LOG(LogLevel::Debug, ("Starting up Offline MediaStreamGraph %p", graph));
 

dom/media/MediaStreamGraph.h

@@ -1195,22 +1195,33 @@ protected:
 };
 
 /**
- * Initially, at least, we will have a singleton MediaStreamGraph per
- * process.  Each OfflineAudioContext object creates its own MediaStreamGraph
- * object too.
+ * There can be multiple MediaStreamGraph per process: one per AudioChannel.
+ * Additionaly, each OfflineAudioContext object creates its own MediaStreamGraph
+ * object too..
  */
 class MediaStreamGraph
 {
 public:
+
   // We ensure that the graph current time advances in multiples of
   // IdealAudioBlockSize()/AudioStream::PreferredSampleRate(). A stream that
   // never blocks and has a track with the ideal audio rate will produce audio
   // in multiples of the block size.
   //
 
+  // Initializing an graph that outputs audio can be quite long on some
+  // platforms. Code that want to output audio at some point can express the
+  // fact that they will need an audio stream at some point by passing
+  // AUDIO_THREAD_DRIVER when getting an instance of MediaStreamGraph, so that
+  // the graph starts with the right driver.
+  enum GraphDriverType {
+    AUDIO_THREAD_DRIVER,
+    SYSTEM_THREAD_DRIVER,
+    OFFLINE_THREAD_DRIVER
+  };
   // Main thread only
-  static MediaStreamGraph* GetInstance(bool aStartWithAudioDriver = false,
-                                       dom::AudioChannel aChannel = dom::AudioChannel::Normal);
+  static MediaStreamGraph* GetInstance(GraphDriverType aGraphDriverRequested,
+                                       dom::AudioChannel aChannel);
   static MediaStreamGraph* CreateNonRealtimeInstance(TrackRate aSampleRate);
   // Idempotent
   static void DestroyNonRealtimeInstance(MediaStreamGraph* aGraph);

dom/media/MediaStreamGraphImpl.h

@@ -93,16 +93,16 @@ public:
   NS_DECL_NSIMEMORYREPORTER
 
   /**
-   * Set aRealtime to true in order to create a MediaStreamGraph which provides
-   * support for real-time audio and video.  Set it to false in order to create
-   * a non-realtime instance which just churns through its inputs and produces
-   * output.  Those objects currently only support audio, and are used to
-   * implement OfflineAudioContext.  They do not support MediaStream inputs.
+   * Use aGraphDriverRequested with SYSTEM_THREAD_DRIVER or AUDIO_THREAD_DRIVER
+   * to create a MediaStreamGraph which provides support for real-time audio
+   * and/or video.  Set it to false in order to create a non-realtime instance
+   * which just churns through its inputs and produces output.  Those objects
+   * currently only support audio, and are used to implement
+   * OfflineAudioContext.  They do not support MediaStream inputs.
    */
-  explicit MediaStreamGraphImpl(bool aRealtime,
+  explicit MediaStreamGraphImpl(GraphDriverType aGraphDriverRequested,
                                 TrackRate aSampleRate,
-                                bool aStartWithAudioDriver = false,
-                                dom::AudioChannel aChannel = dom::AudioChannel::Normal);
+                                dom::AudioChannel aChannel);
 
   /**
    * Unregisters memory reporting and deletes this instance. This should be