MediaStreamNote: Difference between revisions

MediaStreamNote (view source)

Revision as of 06:27, 28 July 2014

5,286 bytes added , 28 July 2014

→‎MediaStream

Ctai

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@@ Line 1: / Line 1: @@
-=MediaStream=
+==MediaStream from getUserMedia==
+Call flow of getUserMedia:
+<source lang="cpp">
+Navigator::MozGetUserMedia(const MediaStreamConstraints& aConstraints,
+                           NavigatorUserMediaSuccessCallback& aOnSuccess,
+                           NavigatorUserMediaErrorCallback& aOnError,
+                           ErrorResult& aRv)
+{
+  ...
+  MediaManager* manager = MediaManager::Get();
+  aRv = manager->GetUserMedia(privileged, mWindow, aConstraints,
+                              onsuccess, onerror);
+}
+nsresult
+MediaManager::GetUserMedia(bool aPrivileged,
+  nsPIDOMWindow* aWindow, const MediaStreamConstraints& aConstraints,
+  nsIDOMGetUserMediaSuccessCallback* aOnSuccess,
+  nsIDOMGetUserMediaErrorCallback* aOnError)
+{
+  ...
+  StreamListeners* listeners = GetActiveWindows()->Get(windowID);
+  if (!listeners) {
+    listeners = new StreamListeners;
+    GetActiveWindows()->Put(windowID, listeners);
+  }
+  ...
+    // Create a disabled listener to act as a placeholder
+  GetUserMediaCallbackMediaStreamListener* listener =
+    new GetUserMediaCallbackMediaStreamListener(mediaThread, windowID);
+  // No need for locking because we always do this in the main thread.
+  listeners->AppendElement(listener);
+  ...
+  // Pass callbacks and MediaStreamListener along to GetUserMediaRunnable.
+  nsRefPtr<GetUserMediaRunnable> runnable;
+  if (c.mFake) {
+    // Fake stream from default backend.
+    runnable = new GetUserMediaRunnable(c, onSuccess.forget(),
+      onError.forget(), windowID, listener, mPrefs, new MediaEngineDefault());
+  } else {
+    // Stream from default device from WebRTC backend.
+    runnable = new GetUserMediaRunnable(c, onSuccess.forget(),
+      onError.forget(), windowID, listener, mPrefs);
+  }
+  ...
+#ifdef MOZ_B2G_CAMERA
+  if (mCameraManager == nullptr) {
+    mCameraManager = nsDOMCameraManager::CreateInstance(aWindow);
+  }
+#endif
+  ...
+  if (aPrivileged ||
+      (c.mFake && !Preferences::GetBool("media.navigator.permission.fake"))) {
+    mMediaThread->Dispatch(runnable, NS_DISPATCH_NORMAL);
+  } ...
+}
+NS_IMETHOD
+GetUserMediaRunnable::Run()
+{
+  MediaEngine* backend = mBackend;
+  // Was a backend provided?
+  if (!backend) {
+    // backend will become MediaEngineWebRTC.
+    backend = mManager->GetBackend(mWindowID);
+  }
+  // Was a device provided?
+  if (!mDeviceChosen) {
+    // SelectDevice will call void MediaEngineWebRTC::EnumerateVideoDevices(MediaSourceType aMediaSource,
+    //                                                                      nsTArray<nsRefPtr<MediaEngineVideoSource> >* aVSources).
+    // It will new and append MediaEngineWebRTCVideoSource into aVSources.
+    // Then pick the first devive.
+    nsresult rv = SelectDevice(backend);
+    if (rv != NS_OK) {
+      return rv;
+    }
+  }
+  ...
+  ProcessGetUserMedia(((IsOn(mConstraints.mAudio) && mAudioDevice) ?
+                       mAudioDevice->GetSource() : nullptr),
+                      ((IsOn(mConstraints.mVideo) && mVideoDevice) ?
+                       mVideoDevice->GetSource() : nullptr));
+  return NS_OK;
+}
+void
+ProcessGetUserMedia(MediaEngineAudioSource* aAudioSource,
+                    MediaEngineVideoSource* aVideoSource)
+{
+  ...
+  if (aVideoSource) {
+    rv = aVideoSource->Allocate(GetInvariant(mConstraints.mVideo), mPrefs);
+    ...
+  }
+  ...
+  NS_DispatchToMainThread(new GetUserMediaStreamRunnable(
+    mSuccess, mError, mWindowID, mListener, aAudioSource, aVideoSource,
+    peerIdentity
+  ));
+  ...
+}
+NS_IMETHOD
+GetUserMediaStreamRunnable::Run()
+{
+  ...
+  // Create a media stream.
+  nsRefPtr<nsDOMUserMediaStream> trackunion =
+    nsDOMUserMediaStream::CreateTrackUnionStream(window, mAudioSource,
+                                                 mVideoSource);
+  ...
+  MediaStreamGraph* gm = MediaStreamGraph::GetInstance();
+  nsRefPtr<SourceMediaStream> stream = gm->CreateSourceStream(nullptr);
+  ...
+  trackunion->mSourceStream = stream;
+  ...
+  // The listener was added at the beginning in an inactive state.
+  // Activate our listener. We'll call Start() on the source when get a callback
+  // that the MediaStream has started consuming. The listener is freed
+  // when the page is invalidated (on navigation or close).
+  mListener->Activate(stream.forget(), mAudioSource, mVideoSource);
+  ...
+  // This will call to nsresult MediaEngineWebRTCVideoSource::Start(SourceMediaStream* aStream, TrackID aID)
+  nsRefPtr<MediaOperationRunnable> runnable(
+    new MediaOperationRunnable(MEDIA_START, mListener, trackunion,
+                               tracksAvailableCallback,
+                               mAudioSource, mVideoSource, false, mWindowID,
+                               mError.forget()));
+  mediaThread->Dispatch(runnable, NS_DISPATCH_NORMAL);
+  // We won't need mError now.
+  mError = nullptr;
+  return NS_OK;
+}
+SourceMediaStream*
+MediaStreamGraph::CreateSourceStream(DOMMediaStream* aWrapper)
+{
+  SourceMediaStream* stream = new SourceMediaStream(aWrapper);
+  NS_ADDREF(stream);
+  MediaStreamGraphImpl* graph = static_cast<MediaStreamGraphImpl*>(this);
+  stream->SetGraphImpl(graph);
+  graph->AppendMessage(new CreateMessage(stream));
+  return stream;
+}
+virtual void CreateMessage::Run() MOZ_OVERRIDE
+{
+  mStream->GraphImpl()->AddStream(mStream); // It will call mStreams.AppendElement(aStream);
+  mStream->Init();
+}
+</source>