R/PLR calculation - time-based window

webrtc/voice_engine/transport_feedback_packet_loss_tracker.h

 /*
  *  Copyright (c) 2017 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.
  */
 
 #ifndef WEBRTC_VOICE_ENGINE_TRANSPORT_FEEDBACK_PACKET_LOSS_TRACKER_H_
 #define WEBRTC_VOICE_ENGINE_TRANSPORT_FEEDBACK_PACKET_LOSS_TRACKER_H_
 
 #include <map>
 
 #include "webrtc/base/optional.h"
 #include "webrtc/modules/include/module_common_types.h"
 
 namespace webrtc {
 
 namespace rtcp {
 class TransportFeedback;
 }
 
 class TransportFeedbackPacketLossTracker final {
  public:
-  // * Up to |max_acked_packets| latest packet statuses will be used for
-  //   calculating the packet loss metrics.
+  // * |max_window_size_ms| is the time-span of the window's acked part.
+  //   We make sure the TWCC sequence number difference between newest and
+  //   oldest is less than 0x8000, regardless of ack-state, but make sure
+  //   that we only consider up to |max_window_size_ms| of acked data for
+  //   the calculation of the metrics.
   // * PLR (packet-loss-rate) is reliably computable once the statuses of
   //   |plr_min_num_acked_packets| packets are known.
   // * RPLR (recoverable-packet-loss-rate) is reliably computable once the
   //   statuses of |rplr_min_num_acked_pairs| pairs are known.
-  TransportFeedbackPacketLossTracker(size_t max_acked_packets,
+  TransportFeedbackPacketLossTracker(int64_t max_window_size_ms,
                                      size_t plr_min_num_acked_packets,
                                      size_t rplr_min_num_acked_pairs);
 
-  void OnPacketAdded(uint16_t seq_num);
+  void OnPacketAdded(uint16_t seq_num, int64_t send_time_ms);
 
   void OnReceivedTransportFeedback(const rtcp::TransportFeedback& feedback);
 
   // Returns the packet loss rate, if the window has enough packet statuses to
   // reliably compute it. Otherwise, returns empty.
   rtc::Optional<float> GetPacketLossRate() const;
 
   // Returns the first-order-FEC recoverable packet loss rate, if the window has
   // enough status pairs to reliably compute it. Otherwise, returns empty.
   rtc::Optional<float> GetRecoverablePacketLossRate() const;
 
   // Verifies that the internal states are correct. Only used for tests.
   void Validate() const;
 
  private:
   // When a packet is sent, we memorize its association with the stream by
   // marking it as (sent-but-so-far-) unacked. If we ever receive a feedback
   // that reports it as received/lost, we update the state and
   // metrics accordingly.
 
   enum class PacketStatus { Unacked = 0, Received = 1, Lost = 2 };
-  typedef std::map<uint16_t, PacketStatus> PacketStatusMap;
-  typedef PacketStatusMap::const_iterator ConstPacketStatusIterator;
+  struct SentPacket {
+    SentPacket(int64_t send_time_ms, PacketStatus status)
+        : send_time_ms(send_time_ms), status(status) {}
+    int64_t send_time_ms;
+    PacketStatus status;
+  };
+  typedef std::map<uint16_t, SentPacket> SentPacketStatusMap;
+  typedef SentPacketStatusMap::const_iterator ConstPacketStatusIterator;
 
   void Reset();
 
   // ReferenceSequenceNumber() provides a sequence number that defines the
   // order of packet reception info stored in |packet_status_window_|. In
   // particular, given any sequence number |x|,
   // (2^16 + x - ref_seq_num_) % 2^16 defines its actual position in
   // |packet_status_window_|.
   uint16_t ReferenceSequenceNumber() const;
   uint16_t NewestSequenceNumber() const;
-  void RecordFeedback(PacketStatusMap::iterator it, bool received);
+  void RecordPacketStatus(SentPacketStatusMap::iterator it,
+                          PacketStatus new_packet_status);
   void RemoveOldestPacketStatus();
 
   void UpdateMetrics(ConstPacketStatusIterator it,
                      bool apply /* false = undo */);
   void UpdatePlr(ConstPacketStatusIterator it, bool apply /* false = undo */);
   void UpdateRplr(ConstPacketStatusIterator it, bool apply /* false = undo */);
 
   ConstPacketStatusIterator PreviousPacketStatus(
       ConstPacketStatusIterator it) const;
   ConstPacketStatusIterator NextPacketStatus(
       ConstPacketStatusIterator it) const;
 
-  const size_t max_acked_packets_;
+  const int64_t max_window_size_ms_;
   size_t acked_packets_;
 
-  PacketStatusMap packet_status_window_;
+  SentPacketStatusMap packet_status_window_;
   // |ref_packet_status_| points to the oldest item in |packet_status_window_|.
   ConstPacketStatusIterator ref_packet_status_;
 
   // Packet-loss-rate calculation (lost / all-known-packets).
   struct PlrState {
     explicit PlrState(size_t min_num_acked_packets)
         : min_num_acked_packets_(min_num_acked_packets) {
       Reset();
     }
     void Reset() {
@@ skipping 24 matching lines @@
     // of all pairs of consecutive acked packets.
     const size_t min_num_acked_pairs_;
     size_t num_acked_pairs_;
     size_t num_recoverable_losses_;
   } rplr_state_;
 };
 
 }  // namespace webrtc
 
 #endif  // WEBRTC_VOICE_ENGINE_TRANSPORT_FEEDBACK_PACKET_LOSS_TRACKER_H_