Padding is now used to check for continuity in the packet sequence.

webrtc/modules/video_coding/rtp_frame_reference_finder.h

 /*
  *  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 15 matching lines @@
 namespace webrtc {
 namespace video_coding {
 
 class RtpFrameObject;
 class OnCompleteFrameCallback;
 
 class RtpFrameReferenceFinder {
  public:
   explicit RtpFrameReferenceFinder(OnCompleteFrameCallback* frame_callback);
   void ManageFrame(std::unique_ptr<RtpFrameObject> frame);
+  void PaddingReceived(uint16_t seq_num);
 
  private:
   static const uint16_t kPicIdLength = 1 << 7;
   static const uint8_t kMaxTemporalLayers = 5;
   static const int kMaxLayerInfo = 10;
   static const int kMaxStashedFrames = 10;
   static const int kMaxNotYetReceivedFrames = 20;
   static const int kMaxGofSaved = 15;
+  static const int kMaxPaddingAge = 100;
 
   rtc::CriticalSection crit_;
 
+  // Find the relevant group of pictures and update its "last-picture-id-with
+  // padding" sequence number.
+  void UpdateLastPictureIdWithPadding(uint16_t seq_num)
+      EXCLUSIVE_LOCKS_REQUIRED(crit_);
+
   // Retry finding references for all frames that previously didn't have
   // all information needed.
   void RetryStashedFrames() EXCLUSIVE_LOCKS_REQUIRED(crit_);
 
   // Find references for generic frames. If |picture_id| is unspecified
   // then packet sequence numbers will be used to determine the references
   // of the frames.
   void ManageFrameGeneric(std::unique_ptr<RtpFrameObject> frame,
                           int picture_id) EXCLUSIVE_LOCKS_REQUIRED(crit_);
 
@@ skipping 29 matching lines @@
 
   // Check if there is a frame with the up-switch flag set in the interval
   // (|pid_ref|, |picture_id|) with temporal layer smaller than |temporal_idx|.
   bool UpSwitchInIntervalVp9(uint16_t picture_id,
                              uint8_t temporal_idx,
                              uint16_t pid_ref) EXCLUSIVE_LOCKS_REQUIRED(crit_);
 
   // All picture ids are unwrapped to 16 bits.
   uint16_t UnwrapPictureId(uint16_t picture_id) EXCLUSIVE_LOCKS_REQUIRED(crit_);
 
-  // Holds the last sequence number of the last frame that has been created
-  // given the last sequence number of a given keyframe.
-  std::map<uint16_t, uint16_t, DescendingSeqNumComp<uint16_t>> last_seq_num_gop_
-      GUARDED_BY(crit_);
+
+  // For every group of pictures, hold two sequence numbers. The first being
+  // the sequence number of the last packet of the last completed frame, and
+  // the second being the sequence number of the last packet of the last
+  // completed frame advanced by any potential continuous packets of padding.
+  std::map<uint16_t,
+           std::pair<uint16_t, uint16_t>,
+           DescendingSeqNumComp<uint16_t>>
+      last_seq_num_gop_ GUARDED_BY(crit_);
 
   // Save the last picture id in order to detect when there is a gap in frames
   // that have not yet been fully received.
   int last_picture_id_ GUARDED_BY(crit_);
 
+  // Padding packets that have been received but that are not yet continuous
+  // with any group of pictures.
+  std::set<uint16_t, DescendingSeqNumComp<uint16_t>> stashed_padding_
+      GUARDED_BY(crit_);
+
   // The last unwrapped picture id. Used to unwrap the picture id from a length
   // of |kPicIdLength| to 16 bits.
   int last_unwrap_ GUARDED_BY(crit_);
 
   // Frames earlier than the last received frame that have not yet been
   // fully received.
   std::set<uint16_t, DescendingSeqNumComp<uint16_t, kPicIdLength>>
       not_yet_received_frames_ GUARDED_BY(crit_);
 
   // Frames that have been fully received but didn't have all the information
@@ skipping 30 matching lines @@
              kMaxTemporalLayers>
       missing_frames_for_layer_ GUARDED_BY(crit_);
 
   OnCompleteFrameCallback* frame_callback_;
 };
 
 }  // namespace video_coding
 }  // namespace webrtc
 
 #endif  // WEBRTC_MODULES_VIDEO_CODING_RTP_FRAME_REFERENCE_FINDER_H_