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

webrtc/modules/video_coding/packet_buffer.cc

Index: webrtc/modules/video_coding/packet_buffer.cc
diff --git a/webrtc/modules/video_coding/packet_buffer.cc b/webrtc/modules/video_coding/packet_buffer.cc
index ad0054fa84deba79c231f6e3c4aa8160192ac036..4f2db6c7f3dba2af53cfc4d69302126d3906e8bb 100644
--- a/webrtc/modules/video_coding/packet_buffer.cc
+++ b/webrtc/modules/video_coding/packet_buffer.cc
@@ -66,6 +66,12 @@ bool PacketBuffer::InsertPacket(const VCMPacket& packet) {
   if (AheadOf(seq_num, last_seq_num_))
     last_seq_num_ = seq_num;
 
+  // If this is a padding packet, don't insert it.

[stefan-webrtc, 2016/07/05 08:00:40]

In practice this could also be an FEC packet which we just want to notify the
packet buffer about. Maybe mention that too?

[philipel, 2016/07/05 08:41:00]

Done.

+  if (packet.sizeBytes == 0) {
+    reference_finder_.PaddingReceived(packet.seqNum);
+    return true;
+  }
+
   sequence_buffer_[index].frame_begin = packet.isFirstPacket;
   sequence_buffer_[index].frame_end = packet.markerBit;
   sequence_buffer_[index].seq_num = packet.seqNum;