Add TransportFeedbackPacketLossTracker.

webrtc/voice_engine/transport_feedback_packet_loss_tracker.h

Index: webrtc/voice_engine/transport_feedback_packet_loss_tracker.h
diff --git a/webrtc/voice_engine/transport_feedback_packet_loss_tracker.h b/webrtc/voice_engine/transport_feedback_packet_loss_tracker.h
new file mode 100644
index 0000000000000000000000000000000000000000..9f30f2dc23705bbe5b2bc690bf31c60ff5e8996e
--- /dev/null
+++ b/webrtc/voice_engine/transport_feedback_packet_loss_tracker.h
@@ -0,0 +1,82 @@
+/*
+ *  Copyright (c) 2016 The WebRTC project authors. All Rights Reserved.

[kwiberg-webrtc, 2017/01/23 14:04:36]

2017!

This probably applies to other files too.

[minyue-webrtc, 2017/01/23 14:29:38]

Done.

+ *
+ *  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_window_size| latest packet statuses wil be used for calculating
+  // the packet loss metrics. When less than |min_window_size| samples are
+  // available for making a reliable estimation, GetPacketLossRates() will
+  // return false to indicate packet loss metrics are not ready.
+  TransportFeedbackPacketLossTracker(size_t min_window_size,
+                                     size_t max_window_size);
+
+  void OnReceivedTransportFeedback(const rtcp::TransportFeedback& feedback);
+
+  // Returns true if packet loss rate and packet loss episode duration are ready
+  // and assigns respective values to |*packet_loss_rate| and
+  // |*consecutive_packet_loss_rate|. Continuous packet loss rate is defined as
+  // the probability of losing two adjacent packets.
+  bool GetPacketLossRates(float* packet_loss_rate,
+                          float* consecutive_packet_loss_rate) const;
+
+  // Verifies that the internal states are correct. Only used for tests.
+  void Validate() const;
+
+ private:
+  // PacketStatus is a map from sequence number to a boolean. The boolean is
+  // true if it is received.

[kwiberg-webrtc, 2017/01/23 14:04:36]

What does false mean? What does not present mean?

[minyue-webrtc, 2017/01/23 14:29:38]

updated the comment.

[kwiberg-webrtc, 2017/01/23 14:47:17]

Excellent.

+  typedef std::map<uint16_t, bool> PacketStatus;
+  typedef PacketStatus::const_iterator PacketStatusIterator;
+
+  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;
+  bool IsOldSequenceNumber(uint16_t seq_num) const;
+  void InsertPacketStatus(uint16_t seq_num, bool received);
+  void RemoveOldestPacketStatus();
+  void ApplyPacketStatus(PacketStatusIterator it);
+  void UndoPacketStatus(PacketStatusIterator it);
+  PacketStatusIterator PreviousPacketStatus(PacketStatusIterator it);
+  PacketStatusIterator NextPacketStatus(PacketStatusIterator it);
+
+  const size_t min_window_size_;
+  const size_t max_window_size_;
+
+  PacketStatus packet_status_window_;
+  // |ref_packet_status_| points to the oldest item in |packet_status_window_|.
+  PacketStatusIterator ref_packet_status_;
+
+  size_t num_received_packets_;
+  size_t num_lost_packets_;
+  size_t num_consecutive_losses_;
+  size_t num_consecutive_old_reports_;
+};
+
+}  // namespace webrtc
+
+#endif  // WEBRTC_VOICE_ENGINE_TRANSPORT_FEEDBACK_PACKET_LOSS_TRACKER_H_