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..c36c93c976da62166c8bcee30a8c13e4cbd13237
--- /dev/null
+++ b/webrtc/modules/video_coding/nack_module.h
@@ -0,0 +1,112 @@
+/*
+ *  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/thread_annotations.h"
+#include "webrtc/base/thread_checker.h"

[stefan-webrtc, 2016/03/01 08:52:10]

Currently not used

[philipel, 2016/03/01 10:27:07]

Done.

+#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/distribution.h"
+#include "webrtc/system_wrappers/include/clock.h"
+#include "webrtc/system_wrappers/include/critical_section_wrapper.h"

[stefan-webrtc, 2016/03/01 08:52:10]

Use webrtc/base/criticalsection.h instead

[philipel, 2016/03/01 10:27:07]

Done.

+
+namespace webrtc {
+
+class NackModule : public Module {
+ public:
+  NackModule(Clock* clock,
+             VCMNackSender* nack_sender,
+             VCMKeyFrameRequestSender* 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;
+  int32_t Process() override;
+
+ private:
+  // Which fields to consider when deciding
+  // which packet to nack in GetNackBatch.

[stefan-webrtc, 2016/03/01 08:52:11]

Format comment so that it uses the full line length.

[philipel, 2016/03/01 10:27:06]

Done.

+  enum NackFilterOptions {kSeqNumOnly, kTimeOnly, kSeqNumAndTime};

[stefan-webrtc, 2016/03/01 08:52:10]

kSeqNumAndTime doesn't seem to be used?

+
+  // 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.

[stefan-webrtc, 2016/03/01 08:52:11]

Reformat

[philipel, 2016/03/01 10:27:06]

Done.

+  bool RemovePacketsUntilKeyframe()
+      EXCLUSIVE_LOCKS_REQUIRED(crit_);
+  void RemovePacketFromNack(uint16_t seq_num)
+      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.

[stefan-webrtc, 2016/03/01 08:52:11]

Reformat

[philipel, 2016/03/01 10:27:06]

Done.

+  int WaitNumberOfPackets(float probability) const
+      EXCLUSIVE_LOCKS_REQUIRED(crit_);
+
+  rtc::CriticalSection crit_;

[stefan-webrtc, 2016/03/01 08:52:11]

Maybe move the crit down to the group of members that are protected by it.

[philipel, 2016/03/01 10:27:06]

Acknowledged.

+  Clock* const clock_;
+  VCMNackSender* const nack_sender_;
+  VCMKeyFrameRequestSender* const keyframe_request_sender_;
+
+  struct SeqNumComparator {
+    SeqNumComparator() {
+      // Alowes the comparator to wrap back one time in order to compare
+      // sequence numbers before an actual wrap has occured.
+      unwrapper_.UpdateLast(0x20000);
+    }
+    bool operator()(uint16_t s1, uint16_t s2) {
+      return unwrapper_.Unwrap(s1) < unwrapper_.Unwrap(s2);
+    }
+    SequenceNumberUnwrapper unwrapper_;

[stefan-webrtc, 2016/03/01 08:52:10]

I'd prefer to get rid of the state and instead build the comparator using
IsNewerSequenceNumber() from module_common_types.h

[philipel, 2016/03/01 10:27:06]

Done.

+  };
+
+  std::map<int16_t, NackInfo, SeqNumComparator> nack_list_ GUARDED_BY(crit_);

[stefan-webrtc, 2016/03/01 08:52:10]

Comment on what the int16_t represent here and below.

Should uint16_t right?

[philipel, 2016/03/01 10:27:06]

Yes, should be uint16_t.

+  std::set<int16_t, SeqNumComparator> keyframe_list_ GUARDED_BY(crit_);
+  Distribution reordering_distribution_;
+  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_