Drop back to back frames in VideoFrameResolutionAdapter::MaybeDropFrame.

content/renderer/media/video_track_adapter.cc

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "content/renderer/media/video_track_adapter.h"
 
 #include <algorithm>
 #include <limits>
 #include <utility>
 
 #include "base/bind.h"
 #include "base/debug/trace_event.h"
 #include "base/location.h"
 #include "base/metrics/histogram.h"
 #include "media/base/video_util.h"
 
 namespace content {
 
 namespace {
 
 // Amount of frame intervals to wait before considering the source as muted, for
 // the first frame and under normal conditions, respectively. First frame might
 // take longer to arrive due to source startup.
 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.
 void ReleaseOriginalFrame(
     const scoped_refptr<media::VideoFrame>& frame) {
 }
 
 void ResetCallbackOnMainRenderThread(
     scoped_ptr<VideoCaptureDeliverFrameCB> callback) {
   // |callback| will be deleted when this exits.
@@ skipping 181 matching lines @@
   }
   DoDeliverFrame(video_frame, format, estimated_capture_time);
 }
 
 bool VideoTrackAdapter::VideoFrameResolutionAdapter::MaybeDropFrame(
     const scoped_refptr<media::VideoFrame>& frame) {
   if (max_frame_rate_ == 0.0f)
     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.
   if (max_frame_rate_ + 0.5f > frame_rate_)
     return false;  // Keep this frame.
 
   // The input frame rate is higher than requested.
   // Decide if we should keep this frame or drop it.
   keep_frame_counter_ += max_frame_rate_ / frame_rate_;
   if (keep_frame_counter_ >= 1) {
@@ skipping 193 matching lines @@
   // Rearm the monitoring while there are active Tracks, i.e. as long as the
   // owner MediaStreamSource is active.
   io_message_loop_->PostDelayedTask(FROM_HERE,
       base::Bind(&VideoTrackAdapter::CheckFramesReceivedOnIO, this,
           set_muted_state_callback, frame_counter_),
       base::TimeDelta::FromSecondsD(kNormalFrameTimeoutInFrameIntervals /
                                     source_frame_rate_));
 }
 
 }  // namespace content