Clear the FrameBuffer in case of backward jumps in the picture id.

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 117 matching lines @@
     }
     float rtt_mult = protection_mode_ == kProtectionNackFEC ? 0.0 : 1.0;
     timing_->SetJitterDelay(jitter_estimator_->GetJitterEstimate(rtt_mult));
     timing_->UpdateCurrentDelay(frame->RenderTime(),
                                 clock_->TimeInMilliseconds());
 
     UpdateJitterDelay();
 
     PropagateDecodability(next_frame_it->second);
     AdvanceLastDecodedFrame(next_frame_it);
+    last_decoded_frame_timestamp_ = frame->timestamp;
     *frame_out = std::move(frame);
     return kFrameFound;
   } else {
     return kTimeout;
   }
 }
 
 void FrameBuffer::SetProtectionMode(VCMVideoProtection mode) {
   rtc::CritScope lock(&crit_);
   protection_mode_ = mode;
@@ skipping 34 matching lines @@
 
   if (frame->inter_layer_predicted && frame->spatial_layer == 0) {
     LOG(LS_WARNING) << "Frame with (picture_id:spatial_id) (" << key.picture_id
                     << ":" << static_cast<int>(key.spatial_layer)
                     << ") is marked as inter layer predicted, dropping frame.";
     return last_continuous_picture_id;
   }
 
   if (last_decoded_frame_it_ != frames_.end() &&
       key < last_decoded_frame_it_->first) {
-    LOG(LS_WARNING) << "Frame with (picture_id:spatial_id) (" << key.picture_id
-                    << ":" << 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;
+    if (AheadOf(frame->timestamp, last_decoded_frame_timestamp_) &&
+        frame->num_references == 0) {
+      // If this frame has a newer timestamp but an earlier picture id then we
+      // assume there has been a jump in the picture id due to some encoder
+      // reconfiguration or some other reason. Even though this is not according
+      // to spec we can still continue to decode from this frame if it is a
+      // keyframe.
+      LOG(LS_WARNING) << "A jump in picture id was detected, clearing buffer.";
+      ClearFramesAndHistory();
+      last_continuous_picture_id = -1;
+    } else {
+      LOG(LS_WARNING) << "Frame with (picture_id:spatial_id) ("
+                      << key.picture_id << ":"
+                      << 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;
+    }
   }
 
   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;
   }
@@ skipping 173 matching lines @@
     RTC_HISTOGRAM_COUNTS_1000("WebRTC.Video.KeyFramesReceivedInPermille",
                               key_frames_permille);
   }
 
   if (accumulated_delay_samples_ > 0) {
     RTC_HISTOGRAM_COUNTS_10000("WebRTC.Video.JitterBufferDelayInMs",
                                accumulated_delay_ / accumulated_delay_samples_);
   }
 }
 
+void FrameBuffer::ClearFramesAndHistory() {
+  frames_.clear();
+  last_decoded_frame_it_ = frames_.end();
+  last_continuous_frame_it_ = frames_.end();
+  num_frames_history_ = 0;
+  num_frames_buffered_ = 0;
+}
+
 }  // namespace video_coding
 }  // namespace webrtc