Bug 1218311 - Port the fix of bug 1193614 to VideoSink. r=cpearce. f=dglastonbury.

dom/media/MediaDecoderStateMachine.cpp

@@ -890,19 +890,6 @@ MediaDecoderStateMachine::OnVideoDecoded(MediaData* aVideoSample)
         StopPrerollingVideo();
       }
 
-      // Schedule the state machine to send stream data as soon as possible if
-      // the VideoQueue() is empty or contains one frame before the Push().
-      //
-      // The state machine threads requires a frame in VideoQueue() that is `in
-      // the future` to gather precise timing information. The head of
-      // VideoQueue() is always `in the past`.
-      //
-      // Schedule the state machine as soon as possible to render the video
-      // frame or delay the state machine thread accurately.
-      if (VideoQueue().GetSize() <= 2) {
-        ScheduleStateMachine();
-      }
-
       // For non async readers, if the requested video sample was slow to
       // arrive, increase the amount of audio we buffer to ensure that we
       // don't run out of audio. This is unnecessary for async readers,

dom/media/mediasink/VideoSink.cpp

@@ -221,9 +221,15 @@ void
 VideoSink::OnVideoQueueEvent()
 {
   AssertOwnerThread();
-  // Listen to push event, VideoSink should try rendering ASAP if first frame
-  // arrives but update scheduler is not triggered yet.
-  TryUpdateRenderedVideoFrames();
+
+  // The video queue is empty or contains only one frame before Push() which
+  // means we are slow in video decoding and don't have enough information to
+  // schedule next render loop accurately (default timeout is 40ms). We need
+  // to render incoming frames immediately so render loop can be scheduled
+  // again accurately.
+  if (mAudioSink->IsPlaying() && VideoQueue().GetSize() <= 2) {
+    UpdateRenderedVideoFrames();
+  }
 }
 
 void