Bug Fix: Remote Video Hang For Apprtc Loopback

content/renderer/media/webmediaplayer_ms_compositor.cc

Index: content/renderer/media/webmediaplayer_ms_compositor.cc
diff --git a/content/renderer/media/webmediaplayer_ms_compositor.cc b/content/renderer/media/webmediaplayer_ms_compositor.cc
index 7bd992de607e8b0921affac52f3cc1a0716db05c..6448c0ea3b1530672d7586250b198cadc6e54e7b 100644
--- a/content/renderer/media/webmediaplayer_ms_compositor.cc
+++ b/content/renderer/media/webmediaplayer_ms_compositor.cc
@@ -185,6 +185,7 @@ void WebMediaPlayerMSCompositor::EnqueueFrame(
   base::AutoLock auto_lock(current_frame_lock_);
   ++total_frame_count_;
 
+  // With algorithm off, just let |current_frame_| hold the incoming |frame|.
   if (!rendering_frame_buffer_) {
     SetCurrentFrame(frame);
     return;
@@ -200,6 +201,9 @@ void WebMediaPlayerMSCompositor::EnqueueFrame(
     return;
   }
 
+  // If we detect a bad frame without |render_time|, we switch off algorithm,
+  // because without |render_time|, algorithm cannot work.
+  // In general, this should not happen.
   base::TimeTicks render_time;
   if (!frame->metadata()->GetTimeTicks(
           media::VideoFrameMetadata::REFERENCE_TIME, &render_time)) {
@@ -211,20 +215,19 @@ void WebMediaPlayerMSCompositor::EnqueueFrame(
     return;
   }
 
-  timestamps_to_clock_times_[frame->timestamp()] = render_time;
-
-  rendering_frame_buffer_->EnqueueFrame(frame);
-
+  // This block considers the case that vsyncs stops rendering frames.

[DaleCurtis, 2016/03/09 21:54:01]

"The code below handles the case where UpdateCurrentFrame() callbacks stop.
These callbacks can stop when the tab is hidden or the page area containing the
video frame is scrolled out of view. Since some hardware decoders only have a
limited number of output frames, we must aggressively release frames in this
case."

[qiangchen, 2016/03/09 22:46:40]

Done.

+  // A probable cause is that the tab is inactive.
+  // Nevertheless we still have to let old frames go.
   const base::TimeTicks now = base::TimeTicks::Now();
-  if (now <= last_deadline_max_)
-    return;
-
-  // This shows vsyncs stops rendering frames. A probable cause is that the
-  // tab is not in the front. But we still have to let old frames go.
-  const base::TimeTicks deadline_max =
-      std::max(now, last_deadline_max_ + last_render_length_);
+  if (now > last_deadline_max_ && current_frame_) {
+    dropped_frame_count_ += rendering_frame_buffer_->frames_queued() - 1;

[DaleCurtis, 2016/03/09 21:54:01]

Add a comment explaining why the -1.

[qiangchen, 2016/03/09 22:46:40]

Done.

+    rendering_frame_buffer_->Reset();
+    timestamps_to_clock_times_.clear();
+    SetCurrentFrame(frame);
+  }
 
-  Render(deadline_max - last_render_length_, deadline_max);
+  timestamps_to_clock_times_[frame->timestamp()] = render_time;
+  rendering_frame_buffer_->EnqueueFrame(frame);
 }
 
 bool WebMediaPlayerMSCompositor::UpdateCurrentFrame(