Adds overuse predictor to GoogCC.

Bug: webrtc:10498
Change-Id: Ic97c16d28cbc1e30609f6c1daa3a61423d44641c
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/136924
Commit-Queue: Sebastian Jansson <srte@webrtc.org>
Reviewed-by: Jonas Olsson <jonasolsson@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#28012}

modules/congestion_controller/goog_cc/overuse_predictor.cc

@@ -0,0 +1,72 @@
+/*
+ *  Copyright 2019 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/overuse_predictor.h"
+
+#include <algorithm>
+
+namespace webrtc {
+namespace {
+constexpr int kMaxPendingPackets = 100;
+
+DataRate GetAvailableCapacity(const NetworkStateEstimate& est,
+                              double deviation) {
+  double capacity_bps = est.link_capacity.bps();
+  double min_capacity_bps = est.link_capacity_min.bps();
+  double deviation_bps = est.link_capacity_std_dev.bps();
+  return DataRate::bps(
+      std::max(capacity_bps + deviation_bps * deviation, min_capacity_bps));
+}
+}  // namespace
+
+OverusePredictorConfig::OverusePredictorConfig(const std::string& config) {
+  ParseFieldTrial({&enabled, &capacity_dev_ratio_threshold, &capacity_deviation,
+                   &delay_threshold},
+                  config);
+}
+
+OverusePredictor::OverusePredictor(const WebRtcKeyValueConfig* config)
+    : conf_(config->Lookup("WebRTC-Bwe-OverusePredictor")) {}
+
+bool OverusePredictor::Enabled() const {
+  return conf_.enabled;
+}
+
+void OverusePredictor::OnSentPacket(SentPacket sent_packet) {
+  pending_.push_back(SentPacketInfo{sent_packet.send_time, sent_packet.size});
+  if (pending_.size() > kMaxPendingPackets)
+    pending_.pop_front();
+}
+
+bool OverusePredictor::PredictOveruse(const NetworkStateEstimate& est) {
+  while (!pending_.empty() && pending_.front().send_time < est.last_send_time) {
+    pending_.pop_front();
+  }
+  double deviation_ratio = est.link_capacity_std_dev / est.link_capacity;
+  if (deviation_ratio > conf_.capacity_dev_ratio_threshold)
+    return false;
+  TimeDelta buffer_delay = PredictDelay(est) - est.propagation_delay;
+  return buffer_delay > conf_.delay_threshold;
+}
+
+TimeDelta OverusePredictor::PredictDelay(const NetworkStateEstimate& est) {
+  auto safe_capacity = GetAvailableCapacity(est, conf_.capacity_deviation);
+  Timestamp last_send_time = est.last_send_time;
+  TimeDelta link_delay = est.pre_link_buffer_delay;
+  for (const auto& packet : pending_) {
+    auto delta = packet.send_time - last_send_time;
+    last_send_time = packet.send_time;
+    link_delay = std::max(link_delay - delta, est.propagation_delay);
+    link_delay += packet.size / safe_capacity;
+  }
+  return link_delay;
+}
+
+}  // namespace webrtc