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

webrtc/modules/congestion_controller/trendline_estimator.cc

+/*
+ *  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/logging.h"
+#include "webrtc/modules/remote_bitrate_estimator/include/bwe_defines.h"
+#include "webrtc/modules/remote_bitrate_estimator/test/bwe_test_logging.h"
+
+namespace webrtc {
+
+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),
+      last_smoothed_delay_(0),
+      accumulated_delay_hist_(),
+      sum_x_(0),
+      sum_y_(0),
+      sum_xy_(0),
+      sum_x2_(0),
+      trendline_(0) {}
+
+TrendlineEstimator::~TrendlineEstimator() {}
+
+void TrendlineEstimator::Update(double recv_delta_ms,
+                                double send_delta_ms,
+                                int64_t 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_);
+  last_smoothed_delay_ = smoothed_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.
+  accumulated_delay_hist_.push_back(std::make_pair(now_ms, smoothed_delay_));
+  sum_x_ += now_ms;
+  sum_y_ += smoothed_delay_;
+  sum_xy_ += static_cast<double>(now_ms) * static_cast<double>(smoothed_delay_);
+  sum_x2_ += static_cast<double>(now_ms) * static_cast<double>(now_ms);
+  if (accumulated_delay_hist_.size() > window_size_) {
+    sum_x_ -= accumulated_delay_hist_.front().first;
+    sum_y_ -= accumulated_delay_hist_.front().second;
+    sum_xy_ -= static_cast<double>(accumulated_delay_hist_.front().first) *
+               static_cast<double>(accumulated_delay_hist_.front().second);
+    sum_x2_ -= static_cast<double>(accumulated_delay_hist_.front().first) *
+               static_cast<double>(accumulated_delay_hist_.front().first);
+    accumulated_delay_hist_.pop_front();
+  }
+  if (accumulated_delay_hist_.size() == window_size_) {
+    trendline_ = (window_size_ * sum_xy_ - sum_x_ * sum_y_) /
+                 (window_size_ * sum_x2_ - sum_x_ * sum_x_);
+  }
+
+  BWE_TEST_LOGGING_PLOT(1, "trendline_slope", now_ms, trendline_);
+}
+
+}  // namespace webrtc