Implement the NackModule as part of the new jitter buffer.

webrtc/modules/video_coding/nack_module.h

Index: webrtc/modules/video_coding/nack_module.h
diff --git a/webrtc/modules/video_coding/nack_module.h b/webrtc/modules/video_coding/nack_module.h
new file mode 100644
index 0000000000000000000000000000000000000000..a98bb4ef5827ea499c393cbb9b4b23f2f119e0af
--- /dev/null
+++ b/webrtc/modules/video_coding/nack_module.h
@@ -0,0 +1,103 @@
+/*
+ *  Copyright (c) 2016 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_MODULES_VIDEO_CODING_NACK_MODULE_H_
+#define WEBRTC_MODULES_VIDEO_CODING_NACK_MODULE_H_
+
+#include <map>
+#include <vector>
+#include <set>
+
+#include "webrtc/base/criticalsection.h"
+#include "webrtc/base/thread_annotations.h"
+#include "webrtc/modules/include/module.h"
+#include "webrtc/modules/video_coding/include/video_coding_defines.h"
+#include "webrtc/modules/video_coding/packet.h"
+#include "webrtc/modules/video_coding/histogram.h"
+#include "webrtc/system_wrappers/include/clock.h"
+
+namespace webrtc {
+
+
+class NackModule : public Module {
+ public:
+  NackModule(Clock* clock,
+             NackSender* nack_sender,
+             KeyFrameRequestSender* keyframe_request_sender);
+
+  void OnReceivedPacket(const VCMPacket& packet);
+  void ClearUpTo(uint16_t seq_num);
+  void UpdateRtt(int64_t rtt_ms);
+  void Stop();
+
+  // Module implementation
+  int64_t TimeUntilNextProcess() override;
+  void Process() override;
+
+ private:
+  // Which fields to consider when deciding which packet to nack in
+  // GetNackBatch.
+  enum NackFilterOptions { kSeqNumOnly, kTimeOnly, kSeqNumAndTime };
+
+  // This class holds the sequence number of the packet that is in the nack list
+  // as well as the meta data about when it should be nacked and how many times
+  // we have tried to nack this packet.
+  struct NackInfo {
+    NackInfo();
+    NackInfo(uint16_t seq_num, uint16_t send_at_seq_num);
+
+    uint16_t seq_num;
+    uint16_t send_at_seq_num;
+    int64_t sent_at_time;
+    int retries;
+  };
+
+  void AddPacketsToNack(uint16_t seq_num_start, uint16_t seq_num_end)
+      EXCLUSIVE_LOCKS_REQUIRED(crit_);
+
+  // Removes packets from the nack list until the next keyframe. Returns true
+  // if packets were removed.
+  bool RemovePacketsUntilKeyFrame() EXCLUSIVE_LOCKS_REQUIRED(crit_);
+  std::vector<uint16_t> GetNackBatch(NackFilterOptions options)
+      EXCLUSIVE_LOCKS_REQUIRED(crit_);
+
+  // Update the reordering distribution.
+  void UpdateReorderingStatistics(uint16_t seq_num)
+      EXCLUSIVE_LOCKS_REQUIRED(crit_);
+
+  // Returns how many packets we have to wait in order to receive the packet
+  // with probability |probabilty| or higher.
+  int WaitNumberOfPackets(float probability) const
+      EXCLUSIVE_LOCKS_REQUIRED(crit_);
+
+  rtc::CriticalSection crit_;
+  Clock* const clock_;
+  NackSender* const nack_sender_;
+  KeyFrameRequestSender* const keyframe_request_sender_;
+
+  struct SeqNumComparator {
+    bool operator()(uint16_t s1, uint16_t s2) {
+      return IsNewerSequenceNumber(s2, s1);
+    }
+  };

[stefan-webrtc, 2016/03/01 12:16:34]

Prefer moving this up to the other types, e.g., NackInfo

[philipel, 2016/03/01 13:31:09]

Done.

+
+  std::map<uint16_t, NackInfo, SeqNumComparator> nack_list_ GUARDED_BY(crit_);
+  std::set<uint16_t, SeqNumComparator> keyframe_list_ GUARDED_BY(crit_);
+  video_coding::Histogram reordering_histogram_;

[stefan-webrtc, 2016/03/01 12:16:34]

Does this not have to be guarded by crit_? In that case move it from this group
of members.

[philipel, 2016/03/01 13:31:09]

Should be guarded by crit_, fixed.

+  bool running_ GUARDED_BY(crit_);
+  bool initialized_ GUARDED_BY(crit_);
+  int64_t rtt_ms_ GUARDED_BY(crit_);
+  uint16_t last_seq_num_ GUARDED_BY(crit_);
+  int64_t next_process_time_ms_ GUARDED_BY(crit_);
+};
+
+}  // namespace webrtc
+
+#endif  // WEBRTC_MODULES_VIDEO_CODING_NACK_MODULE_H_