Add statistics gathering for packet loss.

webrtc/modules/rtp_rtcp/source/packet_loss_stats.cc

+/*
+ *  Copyright (c) 2015 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.
+ */
+
+#include "webrtc/modules/rtp_rtcp/source/packet_loss_stats.h"
+
+#include <vector>
+
+#include "webrtc/base/checks.h"
+
+// After this many packets are added, adding additional packets will cause the
+// oldest packets to be pruned from the buffer.
+static const int kBufferSize = 100;
+
+namespace webrtc {
+
+PacketLossStats::PacketLossStats()
+    : single_loss_historic_count_(0),
+      multiple_loss_historic_event_count_(0),
+      multiple_loss_historic_packet_count_(0) {
+}
+
+void PacketLossStats::AddLostPacket(uint16_t sequence_number) {
+  // Detect sequence number wrap around.
+  if (!lost_packets_buffer_.empty() &&
+      static_cast<int>(*(lost_packets_buffer_.rbegin())) - sequence_number
+      > 0x8000) {
+    // The buffer contains large numbers and this is a small number.
+    lost_packets_wrapped_buffer_.insert(sequence_number);
+  } else {
+    lost_packets_buffer_.insert(sequence_number);
+  }
+  if (lost_packets_wrapped_buffer_.size() + lost_packets_buffer_.size()
+      > kBufferSize || (!lost_packets_wrapped_buffer_.empty() &&
+                        *(lost_packets_wrapped_buffer_.rbegin()) > 0x4000)) {
+    PruneBuffer();
+  }
+}
+
+int PacketLossStats::GetSingleLossCount() const {
+  int single_loss_count, unused1, unused2;
+  ComputeLossCounts(&single_loss_count, &unused1, &unused2);
+  return single_loss_count;
+}
+
+int PacketLossStats::GetMultipleLossEventCount() const {
+  int event_count, unused1, unused2;
+  ComputeLossCounts(&unused1, &event_count, &unused2);
+  return event_count;
+}
+
+int PacketLossStats::GetMultipleLossPacketCount() const {
+  int packet_count, unused1, unused2;
+  ComputeLossCounts(&unused1, &unused2, &packet_count);
+  return packet_count;
+}
+
+void PacketLossStats::ComputeLossCounts(
+    int* out_single_loss_count,
+    int* out_multiple_loss_event_count,
+    int* out_multiple_loss_packet_count) const {
+  *out_single_loss_count = single_loss_historic_count_;
+  *out_multiple_loss_event_count = multiple_loss_historic_event_count_;
+  *out_multiple_loss_packet_count = multiple_loss_historic_packet_count_;
+  if (lost_packets_buffer_.empty()) {
+    DCHECK(lost_packets_wrapped_buffer_.empty());
+    return;
+  }
+  uint16_t last_num = 0;
+  int sequential_count = 0;
+  std::vector<const std::set<uint16_t>*> buffers;
+  buffers.push_back(&lost_packets_buffer_);
+  buffers.push_back(&lost_packets_wrapped_buffer_);
+  for (auto buffer : buffers) {
+    for (auto it = buffer->begin(); it != buffer->end(); ++it) {
+      uint16_t current_num = *it;
+      if (sequential_count > 0 && current_num != ((last_num + 1) & 0xFFFF)) {
+        if (sequential_count == 1) {
+          (*out_single_loss_count)++;
+        } else {
+          (*out_multiple_loss_event_count)++;
+          *out_multiple_loss_packet_count += sequential_count;
+        }
+        sequential_count = 0;
+      }
+      sequential_count++;
+      last_num = current_num;
+    }
+  }
+  if (sequential_count == 1) {
+    (*out_single_loss_count)++;
+  } else if (sequential_count > 1) {
+    (*out_multiple_loss_event_count)++;
+    *out_multiple_loss_packet_count += sequential_count;
+  }
+}
+
+void PacketLossStats::PruneBuffer() {
+  // Remove the oldest lost packet and any contiguous packets and move them
+  // into the historic counts.
+  auto it = lost_packets_buffer_.begin();
+  uint16_t last_removed = 0;
+  int remove_count = 0;
+  // Count adjacent packets and continue counting if it is wrap around by
+  // swapping in the wrapped buffer and letting our value wrap as well.
+  while (remove_count == 0 || (!lost_packets_buffer_.empty() &&
+                               *it == ((last_removed + 1) & 0xFFFF))) {
+    last_removed = *it;
+    remove_count++;
+    auto to_erase = it++;
+    lost_packets_buffer_.erase(to_erase);
+    if (lost_packets_buffer_.empty()) {
+      lost_packets_buffer_.swap(lost_packets_wrapped_buffer_);
+      it = lost_packets_buffer_.begin();
+    }
+  }
+  if (remove_count > 1) {
+    multiple_loss_historic_event_count_++;
+    multiple_loss_historic_packet_count_ += remove_count;
+  } else {
+    single_loss_historic_count_++;
+  }
+  // Continue pruning if the wrapped buffer is beyond a threshold and there are
+  // things left in the pre-wrapped buffer.
+  if (!lost_packets_wrapped_buffer_.empty() &&
+      *(lost_packets_wrapped_buffer_.rbegin()) > 0x4000) {
+    PruneBuffer();
+  }
+}
+
+}  // namespace webrtc