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

webrtc/modules/video_coding/rtp_frame_reference_finder.h

Index: webrtc/modules/video_coding/rtp_frame_reference_finder.h
diff --git a/webrtc/modules/video_coding/rtp_frame_reference_finder.h b/webrtc/modules/video_coding/rtp_frame_reference_finder.h
index 5fd67ab2a4a69216db043cb296bbab902e2774bf..c9d3c1e7f426969108eaeca8a3de51e9eb90c645 100644
--- a/webrtc/modules/video_coding/rtp_frame_reference_finder.h
+++ b/webrtc/modules/video_coding/rtp_frame_reference_finder.h
@@ -33,6 +33,7 @@ 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;
@@ -41,9 +42,15 @@ class RtpFrameReferenceFinder {
   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_);
@@ -93,15 +100,25 @@ class RtpFrameReferenceFinder {
   // 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, holds the last sequence number and the
+  // last sequence number with padding included.

[terelius, 2016/07/04 12:03:35]

I'd still like to have this comment clarified.

[philipel, 2016/07/04 12:19:53]

"For every group of pictures, holds the packet sequence number and the the
packet sequence number advanced by continuous packets of padding for the last
completed frame withing that group."

WDYT @terelius?

+  // first  = last sequence number
+  // second = last sequence number with padding included
+  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 is not yet continuous with
+  // any group of pictures.
+  std::set<uint16_t, DescendingSeqNumComp<uint16_t>> received_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_);