Add warning about timestamp non-monotonicity in the frame buffer.

webrtc/modules/video_coding/frame_buffer2.cc

 /*
  *  Copyright (c) 2016 The WebRTC project authors. All Rights Reserved.
  *
  *  Use of this source code is governed by a BSD-style license
  *  that can be found in the LICENSE file in the root of the source
  *  tree. An additional intellectual property rights grant can be found
  *  in the file PATENTS.  All contributing project authors may
  *  be found in the AUTHORS file in the root of the source tree.
  */
 
@@ skipping 126 matching lines @@
 
         float rtt_mult = protection_mode_ == kProtectionNackFEC ? 0.0 : 1.0;
         timing_->SetJitterDelay(jitter_estimator_->GetJitterEstimate(rtt_mult));
         timing_->UpdateCurrentDelay(frame->RenderTime(), now_ms);
       }
 
       UpdateJitterDelay();
 
       PropagateDecodability(next_frame_it_->second);
       AdvanceLastDecodedFrame(next_frame_it_);
+      if (last_decoded_frame_it_ != frames_.end() &&
+          AheadOrAt(last_decoded_frame_timestamp_, frame->timestamp)) {

[brandtr, 2017/04/26 11:26:33]

This is correct being >=, right? I don't think we ever want to send the same
timestamp to the decoder more than once?

[philipel, 2017/04/26 12:27:28]

When we use SVC we will send frame with the same timestamp to the decoder.

What you can do is to check if we send a frame with the same timestamp as the
last frame and (last_decoded_frame_it_->first < key), then we know that this
frame is just a higher spatial layer frame in a superframe.

[brandtr, 2017/04/26 15:16:21]

Right. What about this?

+        int last_decoded_frame_picture_id =
+            last_decoded_frame_it_->first.picture_id;
+        LOG(LS_WARNING) << "Sending frame "
+                        << "(timestamp = " << frame->timestamp
+                        << ", picture_id = " << frame->picture_id
+                        << ") to decoder when last decoded frame was "
+                        << "(timestamp = " << last_decoded_frame_timestamp_
+                        << ", picture_id = " << last_decoded_frame_picture_id
+                        << ").";
+      }
       last_decoded_frame_timestamp_ = frame->timestamp;
       *frame_out = std::move(frame);
       return kFrameFound;
     }
   }
 
   if (latest_return_time_ms - now_ms > 0) {
     // If |next_frame_it_ == frames_.end()| and there is still time left, it
     // means that the frame buffer was cleared as the thread in this function
     // was waiting to acquire |crit_| in order to return. Wait for the
@@ skipping 283 matching lines @@
   frames_.clear();
   last_decoded_frame_it_ = frames_.end();
   last_continuous_frame_it_ = frames_.end();
   next_frame_it_ = frames_.end();
   num_frames_history_ = 0;
   num_frames_buffered_ = 0;
 }
 
 }  // namespace video_coding
 }  // namespace webrtc