Add a new overuse estimator for the delay based BWE behind experiment.

Parse the estimation parameters from the field trial string.

BUG=webrtc:6690

Review-Url: https://codereview.webrtc.org/2489323002
Cr-Commit-Position: refs/heads/master@{#15126}

webrtc/modules/BUILD.gn

@@ -399,6 +399,7 @@ if (rtc_include_tests) {
       "congestion_controller/probe_controller_unittest.cc",
       "congestion_controller/probing_interval_estimator_unittest.cc",
       "congestion_controller/transport_feedback_adapter_unittest.cc",
+      "congestion_controller/trendline_estimator_unittest.cc",
       "media_file/media_file_unittest.cc",
       "module_common_types_unittest.cc",
       "pacing/alr_detector_unittest.cc",

webrtc/modules/congestion_controller/BUILD.gn

@@ -22,8 +22,16 @@ rtc_static_library("congestion_controller") {
     "probing_interval_estimator.h",
     "transport_feedback_adapter.cc",
     "transport_feedback_adapter.h",
+    "trendline_estimator.cc",
+    "trendline_estimator.h",
   ]
 
+  if (rtc_enable_bwe_test_logging) {
+    defines = [ "BWE_TEST_LOGGING_COMPILE_TIME_ENABLE=1" ]
+  } else {
+    defines = [ "BWE_TEST_LOGGING_COMPILE_TIME_ENABLE=0" ]
+  }
+
   # TODO(jschuh): Bug 1348: fix this warning.
   configs += [ "//build/config/compiler:no_size_t_to_int_warning" ]
 

webrtc/modules/congestion_controller/delay_based_bwe.cc

@@ -12,6 +12,7 @@
 
 #include <algorithm>
 #include <cmath>
+#include <string>
 
 #include "webrtc/base/checks.h"
 #include "webrtc/base/constructormagic.h"
@@ -38,15 +39,52 @@ constexpr uint32_t kFixedSsrc = 0;
 constexpr int kInitialRateWindowMs = 500;
 constexpr int kRateWindowMs = 150;
 
+constexpr size_t kDefaultTrendlineWindowSize = 15;
+constexpr double kDefaultTrendlineSmoothingCoeff = 0.9;
+constexpr double kDefaultTrendlineThresholdGain = 4.0;
+
 const char kBitrateEstimateExperiment[] = "WebRTC-ImprovedBitrateEstimate";
+const char kBweTrendlineFilterExperiment[] = "WebRTC-BweTrendlineFilter";
 
 bool BitrateEstimateExperimentIsEnabled() {
   return webrtc::field_trial::FindFullName(kBitrateEstimateExperiment) ==
          "Enabled";
 }
+
+bool TrendlineFilterExperimentIsEnabled() {
+  std::string experiment_string =
+      webrtc::field_trial::FindFullName(kBweTrendlineFilterExperiment);
+  // The experiment is enabled iff the field trial string begins with "Enabled".
+  return experiment_string.find("Enabled") == 0;
+}
+
+bool ReadTrendlineFilterExperimentParameters(size_t* window_points,
+                                             double* smoothing_coef,
+                                             double* threshold_gain) {
+  RTC_DCHECK(TrendlineFilterExperimentIsEnabled());
+  std::string experiment_string =
+      webrtc::field_trial::FindFullName(kBweTrendlineFilterExperiment);
+  int parsed_values = sscanf(experiment_string.c_str(), "Enabled-%zu,%lf,%lf",
+                             window_points, smoothing_coef, threshold_gain);
+  if (parsed_values == 3) {
+    RTC_CHECK_GT(*window_points, 1) << "Need at least 2 points to fit a line.";
+    RTC_CHECK(0 <= *smoothing_coef && *smoothing_coef <= 1)
+        << "Coefficient needs to be between 0 and 1 for weighted average.";
+    RTC_CHECK_GT(*threshold_gain, 0) << "Threshold gain needs to be positive.";
+    return true;
+  }
+  LOG(LS_WARNING) << "Failed to parse parameters for BweTrendlineFilter "
+                     "experiment from field trial string. Using default.";
+  *window_points = kDefaultTrendlineWindowSize;
+  *smoothing_coef = kDefaultTrendlineSmoothingCoeff;
+  *threshold_gain = kDefaultTrendlineThresholdGain;
+  return false;
+}
+
 }  // namespace
 
 namespace webrtc {
+
 DelayBasedBwe::BitrateEstimator::BitrateEstimator()
     : sum_(0),
       current_win_ms_(0),
@@ -132,12 +170,22 @@ rtc::Optional<uint32_t> DelayBasedBwe::BitrateEstimator::bitrate_bps() const {
 DelayBasedBwe::DelayBasedBwe(Clock* clock)
     : clock_(clock),
       inter_arrival_(),
-      estimator_(),
+      kalman_estimator_(),
+      trendline_estimator_(),
       detector_(OverUseDetectorOptions()),
       receiver_incoming_bitrate_(),
       last_update_ms_(-1),
       last_seen_packet_ms_(-1),
-      uma_recorded_(false) {
+      uma_recorded_(false),
+      trendline_window_size_(kDefaultTrendlineWindowSize),
+      trendline_smoothing_coeff_(kDefaultTrendlineSmoothingCoeff),
+      trendline_threshold_gain_(kDefaultTrendlineThresholdGain),
+      in_trendline_experiment_(TrendlineFilterExperimentIsEnabled()) {
+  if (in_trendline_experiment_) {
+    ReadTrendlineFilterExperimentParameters(&trendline_window_size_,
+                                            &trendline_smoothing_coeff_,
+                                            &trendline_threshold_gain_);
+  }
   network_thread_.DetachFromThread();
 }
 
@@ -171,7 +219,10 @@ DelayBasedBwe::Result DelayBasedBwe::IncomingPacketInfo(
     inter_arrival_.reset(
         new InterArrival((kTimestampGroupLengthMs << kInterArrivalShift) / 1000,
                          kTimestampToMs, true));
-    estimator_.reset(new OveruseEstimator(OverUseDetectorOptions()));
+    kalman_estimator_.reset(new OveruseEstimator(OverUseDetectorOptions()));
+    trendline_estimator_.reset(new TrendlineEstimator(
+        trendline_window_size_, trendline_smoothing_coeff_,
+        trendline_threshold_gain_));
   }
   last_seen_packet_ms_ = now_ms;
 
@@ -192,10 +243,19 @@ DelayBasedBwe::Result DelayBasedBwe::IncomingPacketInfo(
                                     info.payload_size, &ts_delta, &t_delta,
                                     &size_delta)) {
     double ts_delta_ms = (1000.0 * ts_delta) / (1 << kInterArrivalShift);
-    estimator_->Update(t_delta, ts_delta_ms, size_delta, detector_.State(),
+    if (in_trendline_experiment_) {
+      trendline_estimator_->Update(t_delta, ts_delta_ms, info.arrival_time_ms);
+      detector_.Detect(trendline_estimator_->trendline_slope(), ts_delta_ms,
+                       trendline_estimator_->num_of_deltas(),
                        info.arrival_time_ms);
-    detector_.Detect(estimator_->offset(), ts_delta_ms,
-                     estimator_->num_of_deltas(), info.arrival_time_ms);
+
+    } else {
+      kalman_estimator_->Update(t_delta, ts_delta_ms, size_delta,
+                                detector_.State(), info.arrival_time_ms);
+      detector_.Detect(kalman_estimator_->offset(), ts_delta_ms,
+                       kalman_estimator_->num_of_deltas(),
+                       info.arrival_time_ms);
+    }
   }
 
   int probing_bps = 0;
@@ -237,8 +297,9 @@ bool DelayBasedBwe::UpdateEstimate(int64_t arrival_time_ms,
                                    int64_t now_ms,
                                    rtc::Optional<uint32_t> acked_bitrate_bps,
                                    uint32_t* target_bitrate_bps) {
-  const RateControlInput input(detector_.State(), acked_bitrate_bps,
-                               estimator_->var_noise());
+  // TODO(terelius): RateControlInput::noise_var is deprecated and will be
+  // removed. In the meantime, we set it to zero.
+  const RateControlInput input(detector_.State(), acked_bitrate_bps, 0);
   rate_control_.Update(&input, now_ms);
   *target_bitrate_bps = rate_control_.UpdateBandwidthEstimate(now_ms);
   return rate_control_.ValidEstimate();

webrtc/modules/congestion_controller/delay_based_bwe.h

@@ -20,6 +20,7 @@
 #include "webrtc/base/rate_statistics.h"
 #include "webrtc/base/thread_checker.h"
 #include "webrtc/modules/congestion_controller/probe_bitrate_estimator.h"
+#include "webrtc/modules/congestion_controller/trendline_estimator.h"
 #include "webrtc/modules/remote_bitrate_estimator/aimd_rate_control.h"
 #include "webrtc/modules/remote_bitrate_estimator/include/remote_bitrate_estimator.h"
 #include "webrtc/modules/remote_bitrate_estimator/inter_arrival.h"
@@ -85,7 +86,8 @@ class DelayBasedBwe {
   rtc::ThreadChecker network_thread_;
   Clock* const clock_;
   std::unique_ptr<InterArrival> inter_arrival_;
-  std::unique_ptr<OveruseEstimator> estimator_;
+  std::unique_ptr<OveruseEstimator> kalman_estimator_;
+  std::unique_ptr<TrendlineEstimator> trendline_estimator_;
   OveruseDetector detector_;
   BitrateEstimator receiver_incoming_bitrate_;
   int64_t last_update_ms_;
@@ -93,6 +95,10 @@ class DelayBasedBwe {
   bool uma_recorded_;
   AimdRateControl rate_control_;
   ProbeBitrateEstimator probe_bitrate_estimator_;
+  size_t trendline_window_size_;
+  double trendline_smoothing_coeff_;
+  double trendline_threshold_gain_;
+  const bool in_trendline_experiment_;
 
   RTC_DISALLOW_IMPLICIT_CONSTRUCTORS(DelayBasedBwe);
 };

webrtc/modules/congestion_controller/delay_based_bwe_unittest.cc

@@ -195,4 +195,38 @@ TEST_F(DelayBasedBweExperimentTest, CapacityDropNegOffsetChange) {
 TEST_F(DelayBasedBweExperimentTest, CapacityDropOneStreamWrap) {
   CapacityDropTestHelper(1, true, 333, 0);
 }
+
+class DelayBasedBweTrendlineExperimentTest : public DelayBasedBweTest {
+ public:
+  DelayBasedBweTrendlineExperimentTest()
+      : override_field_trials_("WebRTC-BweTrendlineFilter/Enabled-15,0.9,4/") {}
+
+ protected:
+  void SetUp() override {
+    bitrate_estimator_.reset(new DelayBasedBwe(&clock_));
+  }
+
+  test::ScopedFieldTrials override_field_trials_;
+};
+
+TEST_F(DelayBasedBweTrendlineExperimentTest, RateIncreaseRtpTimestamps) {
+  RateIncreaseRtpTimestampsTestHelper(1240);
+}
+
+TEST_F(DelayBasedBweTrendlineExperimentTest, CapacityDropOneStream) {
+  CapacityDropTestHelper(1, false, 600, 0);
+}
+
+TEST_F(DelayBasedBweTrendlineExperimentTest, CapacityDropPosOffsetChange) {
+  CapacityDropTestHelper(1, false, 600, 30000);
+}
+
+TEST_F(DelayBasedBweTrendlineExperimentTest, CapacityDropNegOffsetChange) {
+  CapacityDropTestHelper(1, false, 1267, -30000);
+}
+
+TEST_F(DelayBasedBweTrendlineExperimentTest, CapacityDropOneStreamWrap) {
+  CapacityDropTestHelper(1, true, 600, 0);
+}
+
 }  // namespace webrtc

webrtc/modules/congestion_controller/trendline_estimator.cc

@@ -0,0 +1,87 @@
+/*
+ *  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.
+ */
+
+#include "webrtc/modules/congestion_controller/trendline_estimator.h"
+
+#include <algorithm>
+
+#include "webrtc/base/checks.h"
+#include "webrtc/modules/remote_bitrate_estimator/test/bwe_test_logging.h"
+
+namespace webrtc {
+
+namespace {
+double LinearFitSlope(const std::list<std::pair<double, double>> points) {
+  RTC_DCHECK(points.size() >= 2);
+  // Compute the "center of mass".
+  double sum_x = 0;
+  double sum_y = 0;
+  for (const auto& point : points) {
+    sum_x += point.first;
+    sum_y += point.second;
+  }
+  double x_avg = sum_x / points.size();
+  double y_avg = sum_y / points.size();
+  // Compute the slope k = \sum (x_i-x_avg)(y_i-y_avg) / \sum (x_i-x_avg)^2
+  double numerator = 0;
+  double denominator = 0;
+  for (const auto& point : points) {
+    numerator += (point.first - x_avg) * (point.second - y_avg);
+    denominator += (point.first - x_avg) * (point.first - x_avg);
+  }
+  return numerator / denominator;
+}
+}  // namespace
+
+enum { kDeltaCounterMax = 1000 };
+
+TrendlineEstimator::TrendlineEstimator(size_t window_size,
+                                       double smoothing_coef,
+                                       double threshold_gain)
+    : window_size_(window_size),
+      smoothing_coef_(smoothing_coef),
+      threshold_gain_(threshold_gain),
+      num_of_deltas_(0),
+      accumulated_delay_(0),
+      smoothed_delay_(0),
+      delay_hist_(),
+      trendline_(0) {}
+
+TrendlineEstimator::~TrendlineEstimator() {}
+
+void TrendlineEstimator::Update(double recv_delta_ms,
+                                double send_delta_ms,
+                                double now_ms) {
+  const double delta_ms = recv_delta_ms - send_delta_ms;
+  ++num_of_deltas_;
+  if (num_of_deltas_ > kDeltaCounterMax) {
+    num_of_deltas_ = kDeltaCounterMax;
+  }
+
+  // Exponential backoff filter.
+  accumulated_delay_ += delta_ms;
+  BWE_TEST_LOGGING_PLOT(1, "accumulated_delay_ms", now_ms, accumulated_delay_);
+  smoothed_delay_ = smoothing_coef_ * smoothed_delay_ +
+                    (1 - smoothing_coef_) * accumulated_delay_;
+  BWE_TEST_LOGGING_PLOT(1, "smoothed_delay_ms", now_ms, smoothed_delay_);
+
+  // Simple linear regression.
+  delay_hist_.push_back(std::make_pair(now_ms, smoothed_delay_));
+  if (delay_hist_.size() > window_size_) {
+    delay_hist_.pop_front();
+  }
+  if (delay_hist_.size() == window_size_) {
+    trendline_ = LinearFitSlope(delay_hist_);
+  }
+
+  BWE_TEST_LOGGING_PLOT(1, "trendline_slope", now_ms, trendline_);
+}
+
+}  // namespace webrtc

webrtc/modules/congestion_controller/trendline_estimator.h

@@ -0,0 +1,65 @@
+/*
+ *  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_CONGESTION_CONTROLLER_TRENDLINE_ESTIMATOR_H_
+#define WEBRTC_MODULES_CONGESTION_CONTROLLER_TRENDLINE_ESTIMATOR_H_
+
+#include <list>
+#include <utility>
+
+#include "webrtc/base/constructormagic.h"
+#include "webrtc/common_types.h"
+
+namespace webrtc {
+
+class TrendlineEstimator {
+ public:
+  // |window_size| is the number of points required to compute a trend line.
+  // |smoothing_coef| controls how much we smooth out the delay before fitting
+  // the trend line. |threshold_gain| is used to scale the trendline slope for
+  // comparison to the old threshold. Once the old estimator has been removed
+  // (or the thresholds been merged into the estimators), we can just set the
+  // threshold instead of setting a gain.
+  TrendlineEstimator(size_t window_size,
+                     double smoothing_coef,
+                     double threshold_gain);
+  ~TrendlineEstimator();
+
+  // Update the estimator with a new sample. The deltas should represent deltas
+  // between timestamp groups as defined by the InterArrival class.
+  void Update(double recv_delta_ms, double send_delta_ms, double now_ms);
+
+  // Returns the estimated trend k multiplied by some gain.
+  // 0 < k < 1   ->  the delay increases, queues are filling up
+  //   k == 0    ->  the delay does not change
+  //   k < 0     ->  the delay decreases, queues are being emptied
+  double trendline_slope() const { return trendline_ * threshold_gain_; }
+
+  // Returns the number of deltas which the current estimator state is based on.
+  unsigned int num_of_deltas() const { return num_of_deltas_; }
+
+ private:
+  // Parameters.
+  const size_t window_size_;
+  const double smoothing_coef_;
+  const double threshold_gain_;
+  // Used by the existing threshold.
+  unsigned int num_of_deltas_;
+  // Exponential backoff filtering.
+  double accumulated_delay_;
+  double smoothed_delay_;
+  // Linear least squares regression.
+  std::list<std::pair<double, double>> delay_hist_;
+  double trendline_;
+
+  RTC_DISALLOW_COPY_AND_ASSIGN(TrendlineEstimator);
+};
+}  // namespace webrtc
+
+#endif  // WEBRTC_MODULES_CONGESTION_CONTROLLER_TRENDLINE_ESTIMATOR_H_

webrtc/modules/congestion_controller/trendline_estimator_unittest.cc

@@ -0,0 +1,114 @@
+/*
+ *  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.
+ */
+
+#include "webrtc/test/gtest.h"
+#include "webrtc/base/random.h"
+#include "webrtc/modules/congestion_controller/trendline_estimator.h"
+
+namespace webrtc {
+
+namespace {
+constexpr size_t kWindowSize = 15;
+constexpr double kSmoothing = 0.0;
+constexpr double kGain = 1;
+constexpr int64_t kAvgTimeBetweenPackets = 10;
+}  // namespace
+
+TEST(TrendlineEstimator, PerfectLineSlopeOneHalf) {
+  TrendlineEstimator estimator(kWindowSize, kSmoothing, kGain);
+  Random rand(0x1234567);
+  double now_ms = rand.Rand<double>() * 10000;
+  for (size_t i = 1; i < 2 * kWindowSize; i++) {
+    double send_delta = rand.Rand<double>() * 2 * kAvgTimeBetweenPackets;
+    double recv_delta = 2 * send_delta;
+    now_ms += recv_delta;
+    estimator.Update(recv_delta, send_delta, now_ms);
+    if (i < kWindowSize)
+      EXPECT_NEAR(estimator.trendline_slope(), 0, 0.001);
+    else
+      EXPECT_NEAR(estimator.trendline_slope(), 0.5, 0.001);
+  }
+}
+
+TEST(TrendlineEstimator, PerfectLineSlopeMinusOne) {
+  TrendlineEstimator estimator(kWindowSize, kSmoothing, kGain);
+  Random rand(0x1234567);
+  double now_ms = rand.Rand<double>() * 10000;
+  for (size_t i = 1; i < 2 * kWindowSize; i++) {
+    double send_delta = rand.Rand<double>() * 2 * kAvgTimeBetweenPackets;
+    double recv_delta = 0.5 * send_delta;
+    now_ms += recv_delta;
+    estimator.Update(recv_delta, send_delta, now_ms);
+    if (i < kWindowSize)
+      EXPECT_NEAR(estimator.trendline_slope(), 0, 0.001);
+    else
+      EXPECT_NEAR(estimator.trendline_slope(), -1, 0.001);
+  }
+}
+
+TEST(TrendlineEstimator, PerfectLineSlopeZero) {
+  TrendlineEstimator estimator(kWindowSize, kSmoothing, kGain);
+  Random rand(0x1234567);
+  double now_ms = rand.Rand<double>() * 10000;
+  for (size_t i = 1; i < 2 * kWindowSize; i++) {
+    double send_delta = rand.Rand<double>() * 2 * kAvgTimeBetweenPackets;
+    double recv_delta = send_delta;
+    now_ms += recv_delta;
+    estimator.Update(recv_delta, send_delta, now_ms);
+    EXPECT_NEAR(estimator.trendline_slope(), 0, 0.001);
+  }
+}
+
+TEST(TrendlineEstimator, JitteryLineSlopeOneHalf) {
+  TrendlineEstimator estimator(kWindowSize, kSmoothing, kGain);
+  Random rand(0x1234567);
+  double now_ms = rand.Rand<double>() * 10000;
+  for (size_t i = 1; i < 2 * kWindowSize; i++) {
+    double send_delta = rand.Rand<double>() * 2 * kAvgTimeBetweenPackets;
+    double recv_delta = 2 * send_delta + rand.Gaussian(0, send_delta / 3);
+    now_ms += recv_delta;
+    estimator.Update(recv_delta, send_delta, now_ms);
+    if (i < kWindowSize)
+      EXPECT_NEAR(estimator.trendline_slope(), 0, 0.001);
+    else
+      EXPECT_NEAR(estimator.trendline_slope(), 0.5, 0.1);
+  }
+}
+
+TEST(TrendlineEstimator, JitteryLineSlopeMinusOne) {
+  TrendlineEstimator estimator(kWindowSize, kSmoothing, kGain);
+  Random rand(0x1234567);
+  double now_ms = rand.Rand<double>() * 10000;
+  for (size_t i = 1; i < 2 * kWindowSize; i++) {
+    double send_delta = rand.Rand<double>() * 2 * kAvgTimeBetweenPackets;
+    double recv_delta = 0.5 * send_delta + rand.Gaussian(0, send_delta / 25);
+    now_ms += recv_delta;
+    estimator.Update(recv_delta, send_delta, now_ms);
+    if (i < kWindowSize)
+      EXPECT_NEAR(estimator.trendline_slope(), 0, 0.001);
+    else
+      EXPECT_NEAR(estimator.trendline_slope(), -1, 0.1);
+  }
+}
+
+TEST(TrendlineEstimator, JitteryLineSlopeZero) {
+  TrendlineEstimator estimator(kWindowSize, kSmoothing, kGain);
+  Random rand(0x1234567);
+  double now_ms = rand.Rand<double>() * 10000;
+  for (size_t i = 1; i < 2 * kWindowSize; i++) {
+    double send_delta = rand.Rand<double>() * 2 * kAvgTimeBetweenPackets;
+    double recv_delta = send_delta + rand.Gaussian(0, send_delta / 8);
+    now_ms += recv_delta;
+    estimator.Update(recv_delta, send_delta, now_ms);
+    EXPECT_NEAR(estimator.trendline_slope(), 0, 0.1);
+  }
+}
+
+}  // namespace webrtc

webrtc/modules/remote_bitrate_estimator/bwe_simulations.cc

@@ -242,6 +242,19 @@ TEST_P(BweSimulation, PacerGoogleWifiTrace3Mbps) {
   RunFor(300 * 1000);
 }
 
+TEST_P(BweSimulation, PacerGoogleWifiTrace3MbpsLowFramerate) {
+  PeriodicKeyFrameSource source(0, 5, 300, 0, 0, 1000);
+  PacedVideoSender sender(&uplink_, &source, GetParam());
+  RateCounterFilter counter1(&uplink_, 0, "sender_output",
+                             bwe_names[GetParam()]);
+  TraceBasedDeliveryFilter filter(&uplink_, 0, "link_capacity");
+  filter.set_max_delay_ms(500);
+  RateCounterFilter counter2(&uplink_, 0, "Receiver", bwe_names[GetParam()]);
+  PacketReceiver receiver(&uplink_, 0, GetParam(), true, true);
+  ASSERT_TRUE(filter.Init(test::ResourcePath("google-wifi-3mbps", "rx")));
+  RunFor(300 * 1000);
+}
+
 TEST_P(BweSimulation, SelfFairnessTest) {
   Random prng(Clock::GetRealTimeClock()->TimeInMicroseconds());
   const int kAllFlowIds[] = {0, 1, 2, 3};

webrtc/modules/remote_bitrate_estimator/test/plot_dynamics.py

@@ -140,8 +140,13 @@ def main():
   detector_state.addSubplot(['offset_ms'], "Time (s)", "Offset")
   detector_state.addSubplot(['gamma_ms'], "Time (s)", "Gamma")
 
+  trendline_state = Figure("TrendlineState")
+  trendline_state.addSubplot(["accumulated_delay_ms", "smoothed_delay_ms"],
+                             "Time (s)", "Delay (ms)")
+  trendline_state.addSubplot(["trendline_slope"], "Time (s)", "Slope")
+
   # Select which figures to plot here.
-  figures = [receiver, detector_state]
+  figures = [receiver, detector_state, trendline_state]
 
   # Add samples to the figures.
   for line in sys.stdin: