Drop back to back frames in VideoFrameResolutionAdapter::MaybeDropFrame.

content/renderer/media/video_track_adapter.cc

Index: content/renderer/media/video_track_adapter.cc
diff --git a/content/renderer/media/video_track_adapter.cc b/content/renderer/media/video_track_adapter.cc
index ebb47ba9f86b3f0fd4c3d70329706f435ddeff80..3f61a429c46968697e095d9d91b227ac2cdb25ea 100644
--- a/content/renderer/media/video_track_adapter.cc
+++ b/content/renderer/media/video_track_adapter.cc
@@ -24,6 +24,10 @@ namespace {
 const float kFirstFrameTimeoutInFrameIntervals = 100.0f;
 const float kNormalFrameTimeoutInFrameIntervals = 25.0f;
 
+// Min delta time between two frames allowed without being dropped if a max
+// frame rate is specified.
+const int kMinTimeInMsBetweenFrames = 5;
+
 // Empty method used for keeping a reference to the original media::VideoFrame
 // in VideoFrameResolutionAdapter::DeliverFrame if cropping is needed.
 // The reference to |frame| is kept in the closure that calls this method.
@@ -225,11 +229,24 @@ bool VideoTrackAdapter::VideoFrameResolutionAdapter::MaybeDropFrame(
     return false;
 
   base::TimeDelta delta = frame->timestamp() - last_time_stamp_;
+  if (delta.InMilliseconds() < kMinTimeInMsBetweenFrames) {
+    // We have seen video frames being delivered from camera devices back to
+    // back. The simple AR filter for frame rate calculation is too short to
+    // handle that. http://crbug/394315
+    // TODO(perkj): Can we come up with a way to fix the times stamps and the
+    // timing when frames are delivered so all frames can be used?
+    // The time stamps are generated by Chrome and not the actual device.
+    // Most likely the back to back problem is caused by software and not the
+    // actual camera.
+    DVLOG(3) << "Drop frame since delta time since previous frame is "
+             << delta.InMilliseconds() << "ms.";
+    return true;
+  }
   last_time_stamp_ = frame->timestamp();
-  if (delta.ToInternalValue() == 0 || delta == last_time_stamp_)
+  if (delta == last_time_stamp_) // First received frame.
     return false;
-  // Calculate the moving average frame rate. Use a simple filter with 0.1
-  // weight of the current sample.
+  // Calculate the frame rate using a simple AR filter.
+  // Use a simple filter with 0.1 weight of the current sample.
   frame_rate_ = 100 / delta.InMillisecondsF() + 0.9 * frame_rate_;
 
   // Prefer to not drop frames.