Check if the order of frames becomes ambiguous if we were to insert the incoming frame, and if so, …

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 72 matching lines @@
         frame_it = last_decoded_frame_it_;
         ++frame_it;
       }
 
       // |continuous_end_it| points to the first frame after the
       // |last_continuous_frame_it_|.
       auto continuous_end_it = last_continuous_frame_it_;
       if (continuous_end_it != frames_.end())
         ++continuous_end_it;
 
-      for (; frame_it != continuous_end_it; ++frame_it) {
+      for (; frame_it != continuous_end_it && frame_it != frames_.end();
+           ++frame_it) {
         if (!frame_it->second.continuous ||
             frame_it->second.num_missing_decodable > 0) {
           continue;
         }
 
         FrameObject* frame = frame_it->second.frame.get();
         next_frame_it_ = frame_it;
         if (frame->RenderTime() == -1)
           frame->SetRenderTime(timing_->RenderTimeMs(frame->timestamp, now_ms));
         wait_ms = timing_->MaxWaitingTime(frame->RenderTime(), now_ms);
@@ skipping 111 matching lines @@
                       << static_cast<int>(key.spatial_layer)
                       << ") inserted after frame ("
                       << last_decoded_frame_it_->first.picture_id << ":"
                       << static_cast<int>(
                              last_decoded_frame_it_->first.spatial_layer)
                       << ") was handed off for decoding, dropping frame.";
       return last_continuous_picture_id;
     }
   }
 
+  // Test if inserting this frame would cause the order of the frames to become
+  // ambiguous (covering more than half the interval of 2^16). This can happen
+  // when the picture id make large jumps mid stream.
+  if (!frames_.empty() &&
+      key < frames_.begin()->first &&
+      frames_.rbegin()->first < key) {
+    LOG(LS_WARNING) << "A jump in picture id was detected, clearing buffer.";
+    ClearFramesAndHistory();
+    last_continuous_picture_id = -1;
+  }
+
   auto info = frames_.insert(std::make_pair(key, FrameInfo())).first;
 
   if (info->second.frame) {
     LOG(LS_WARNING) << "Frame with (picture_id:spatial_id) (" << key.picture_id
                     << ":" << static_cast<int>(key.spatial_layer)
                     << ") already inserted, dropping frame.";
     return last_continuous_picture_id;
   }
 
   if (!UpdateFrameInfoWithIncomingFrame(*frame, info))
@@ skipping 176 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