1 files changed, 140 insertions, 0 deletions
diff --git a/third_party/libwebrtc/modules/congestion_controller/goog_cc/inter_arrival_delta.cc b/third_party/libwebrtc/modules/congestion_controller/goog_cc/inter_arrival_delta.cc
new file mode 100644
index 0000000000..2d50d08e6a
--- /dev/null
+++ b/third_party/libwebrtc/modules/congestion_controller/goog_cc/inter_arrival_delta.cc
@@ -0,0 +1,140 @@
+/*
+ *  Copyright (c) 2020 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 "modules/congestion_controller/goog_cc/inter_arrival_delta.h"
+
+#include <algorithm>
+
+#include "api/units/time_delta.h"
+#include "api/units/timestamp.h"
+#include "rtc_base/logging.h"
+
+namespace webrtc {
+
+static constexpr TimeDelta kBurstDeltaThreshold = TimeDelta::Millis(5);
+static constexpr TimeDelta kMaxBurstDuration = TimeDelta::Millis(100);
+constexpr TimeDelta InterArrivalDelta::kArrivalTimeOffsetThreshold;
+
+InterArrivalDelta::InterArrivalDelta(TimeDelta send_time_group_length)
+    : send_time_group_length_(send_time_group_length),
+      current_timestamp_group_(),
+      prev_timestamp_group_(),
+      num_consecutive_reordered_packets_(0) {}
+
+bool InterArrivalDelta::ComputeDeltas(Timestamp send_time,
+                                      Timestamp arrival_time,
+                                      Timestamp system_time,
+                                      size_t packet_size,
+                                      TimeDelta* send_time_delta,
+                                      TimeDelta* arrival_time_delta,
+                                      int* packet_size_delta) {
+  bool calculated_deltas = false;
+  if (current_timestamp_group_.IsFirstPacket()) {
+    // We don't have enough data to update the filter, so we store it until we
+    // have two frames of data to process.
+    current_timestamp_group_.send_time = send_time;
+    current_timestamp_group_.first_send_time = send_time;
+    current_timestamp_group_.first_arrival = arrival_time;
+  } else if (current_timestamp_group_.first_send_time > send_time) {
+    // Reordered packet.
+    return false;
+  } else if (NewTimestampGroup(arrival_time, send_time)) {
+    // First packet of a later send burst, the previous packets sample is ready.
+    if (prev_timestamp_group_.complete_time.IsFinite()) {
+      *send_time_delta =
+          current_timestamp_group_.send_time - prev_timestamp_group_.send_time;
+      *arrival_time_delta = current_timestamp_group_.complete_time -
+                            prev_timestamp_group_.complete_time;
+
+      TimeDelta system_time_delta = current_timestamp_group_.last_system_time -
+                                    prev_timestamp_group_.last_system_time;
+
+      if (*arrival_time_delta - system_time_delta >=
+          kArrivalTimeOffsetThreshold) {
+        RTC_LOG(LS_WARNING)
+            << "The arrival time clock offset has changed (diff = "
+            << arrival_time_delta->ms() - system_time_delta.ms()
+            << " ms), resetting.";
+        Reset();
+        return false;
+      }
+      if (*arrival_time_delta < TimeDelta::Zero()) {
+        // The group of packets has been reordered since receiving its local
+        // arrival timestamp.
+        ++num_consecutive_reordered_packets_;
+        if (num_consecutive_reordered_packets_ >= kReorderedResetThreshold) {
+          RTC_LOG(LS_WARNING)
+              << "Packets between send burst arrived out of order, resetting:"
+              << " arrival_time_delta_ms=" << arrival_time_delta->ms()
+              << ", send_time_delta_ms=" << send_time_delta->ms();
+          Reset();
+        }
+        return false;
+      } else {
+        num_consecutive_reordered_packets_ = 0;
+      }
+      *packet_size_delta = static_cast<int>(current_timestamp_group_.size) -
+                           static_cast<int>(prev_timestamp_group_.size);
+      calculated_deltas = true;
+    }
+    prev_timestamp_group_ = current_timestamp_group_;
+    // The new timestamp is now the current frame.
+    current_timestamp_group_.first_send_time = send_time;
+    current_timestamp_group_.send_time = send_time;
+    current_timestamp_group_.first_arrival = arrival_time;
+    current_timestamp_group_.size = 0;
+  } else {
+    current_timestamp_group_.send_time =
+        std::max(current_timestamp_group_.send_time, send_time);
+  }
+  // Accumulate the frame size.
+  current_timestamp_group_.size += packet_size;
+  current_timestamp_group_.complete_time = arrival_time;
+  current_timestamp_group_.last_system_time = system_time;
+
+  return calculated_deltas;
+}
+
+// Assumes that `timestamp` is not reordered compared to
+// `current_timestamp_group_`.
+bool InterArrivalDelta::NewTimestampGroup(Timestamp arrival_time,
+                                          Timestamp send_time) const {
+  if (current_timestamp_group_.IsFirstPacket()) {
+    return false;
+  } else if (BelongsToBurst(arrival_time, send_time)) {
+    return false;
+  } else {
+    return send_time - current_timestamp_group_.first_send_time >
+           send_time_group_length_;
+  }
+}
+
+bool InterArrivalDelta::BelongsToBurst(Timestamp arrival_time,
+                                       Timestamp send_time) const {
+  RTC_DCHECK(current_timestamp_group_.complete_time.IsFinite());
+  TimeDelta arrival_time_delta =
+      arrival_time - current_timestamp_group_.complete_time;
+  TimeDelta send_time_delta = send_time - current_timestamp_group_.send_time;
+  if (send_time_delta.IsZero())
+    return true;
+  TimeDelta propagation_delta = arrival_time_delta - send_time_delta;
+  if (propagation_delta < TimeDelta::Zero() &&
+      arrival_time_delta <= kBurstDeltaThreshold &&
+      arrival_time - current_timestamp_group_.first_arrival < kMaxBurstDuration)
+    return true;
+  return false;
+}
+
+void InterArrivalDelta::Reset() {
+  num_consecutive_reordered_packets_ = 0;
+  current_timestamp_group_ = SendTimeGroup();
+  prev_timestamp_group_ = SendTimeGroup();
+}
+}  // namespace webrtc