GetTransportFeedbackVector() includes unreceived packets, sorted by seq-num

webrtc/modules/rtp_rtcp/include/rtp_rtcp_defines.h

 /*
  *  Copyright (c) 2012 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 261 matching lines @@
                  size_t payload_size,
                  const PacedPacketInfo& pacing_info)
       : creation_time_ms(creation_time_ms),
         arrival_time_ms(arrival_time_ms),
         send_time_ms(send_time_ms),
         sequence_number(sequence_number),
         payload_size(payload_size),
         pacing_info(pacing_info) {}
 
   static constexpr int kNotAProbe = -1;
+  static constexpr int64_t kNotReceived = -1;
 
   // NOTE! The variable |creation_time_ms| is not used when testing equality.
   //       This is due to |creation_time_ms| only being used by SendTimeHistory
   //       for book-keeping, and is of no interest outside that class.
   // TODO(philipel): Remove |creation_time_ms| from PacketFeedback when cleaning
   //                 up SendTimeHistory.
   bool operator==(const PacketFeedback& rhs) const {
     return arrival_time_ms == rhs.arrival_time_ms &&
            send_time_ms == rhs.send_time_ms &&
            sequence_number == rhs.sequence_number &&
            payload_size == rhs.payload_size && pacing_info == rhs.pacing_info;
   }
 
   // Time corresponding to when this object was created.
   int64_t creation_time_ms;
   // Time corresponding to when the packet was received. Timestamped with the
-  // receiver's clock.
+  // receiver's clock. For unreceived packet, the sentinel value kNotReceived
+  // is used.
   int64_t arrival_time_ms;
   // Time corresponding to when the packet was sent, timestamped with the
   // sender's clock.
   int64_t send_time_ms;
   // Packet identifier, incremented with 1 for every packet generated by the
   // sender.
   uint16_t sequence_number;
   // Size of the packet excluding RTP headers.
   size_t payload_size;
   // Pacing information about this packet.
@@ skipping 96 matching lines @@
 class TransportSequenceNumberAllocator {
  public:
   TransportSequenceNumberAllocator() {}
   virtual ~TransportSequenceNumberAllocator() {}
 
   virtual uint16_t AllocateSequenceNumber() = 0;
 };
 
 }  // namespace webrtc
 #endif  // WEBRTC_MODULES_RTP_RTCP_INCLUDE_RTP_RTCP_DEFINES_H_