1 files changed, 166 insertions, 0 deletions
diff --git a/third_party/libwebrtc/modules/congestion_controller/goog_cc/bitrate_estimator.cc b/third_party/libwebrtc/modules/congestion_controller/goog_cc/bitrate_estimator.cc
new file mode 100644
index 0000000000..9c68e48886
--- /dev/null
+++ b/third_party/libwebrtc/modules/congestion_controller/goog_cc/bitrate_estimator.cc
@@ -0,0 +1,166 @@
+/*
+ *  Copyright (c) 2017 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/bitrate_estimator.h"
+
+#include <stdio.h>
+
+#include <algorithm>
+#include <cmath>
+#include <string>
+
+#include "api/units/data_rate.h"
+#include "modules/remote_bitrate_estimator/test/bwe_test_logging.h"
+#include "rtc_base/logging.h"
+
+namespace webrtc {
+
+namespace {
+constexpr int kInitialRateWindowMs = 500;
+constexpr int kRateWindowMs = 150;
+constexpr int kMinRateWindowMs = 150;
+constexpr int kMaxRateWindowMs = 1000;
+
+const char kBweThroughputWindowConfig[] = "WebRTC-BweThroughputWindowConfig";
+
+}  // namespace
+
+BitrateEstimator::BitrateEstimator(const FieldTrialsView* key_value_config)
+    : sum_(0),
+      initial_window_ms_("initial_window_ms",
+                         kInitialRateWindowMs,
+                         kMinRateWindowMs,
+                         kMaxRateWindowMs),
+      noninitial_window_ms_("window_ms",
+                            kRateWindowMs,
+                            kMinRateWindowMs,
+                            kMaxRateWindowMs),
+      uncertainty_scale_("scale", 10.0),
+      uncertainty_scale_in_alr_("scale_alr", uncertainty_scale_),
+      small_sample_uncertainty_scale_("scale_small", uncertainty_scale_),
+      small_sample_threshold_("small_thresh", DataSize::Zero()),
+      uncertainty_symmetry_cap_("symmetry_cap", DataRate::Zero()),
+      estimate_floor_("floor", DataRate::Zero()),
+      current_window_ms_(0),
+      prev_time_ms_(-1),
+      bitrate_estimate_kbps_(-1.0f),
+      bitrate_estimate_var_(50.0f) {
+  // E.g WebRTC-BweThroughputWindowConfig/initial_window_ms:350,window_ms:250/
+  ParseFieldTrial(
+      {&initial_window_ms_, &noninitial_window_ms_, &uncertainty_scale_,
+       &uncertainty_scale_in_alr_, &small_sample_uncertainty_scale_,
+       &small_sample_threshold_, &uncertainty_symmetry_cap_, &estimate_floor_},
+      key_value_config->Lookup(kBweThroughputWindowConfig));
+}
+
+BitrateEstimator::~BitrateEstimator() = default;
+
+void BitrateEstimator::Update(Timestamp at_time, DataSize amount, bool in_alr) {
+  int rate_window_ms = noninitial_window_ms_.Get();
+  // We use a larger window at the beginning to get a more stable sample that
+  // we can use to initialize the estimate.
+  if (bitrate_estimate_kbps_ < 0.f)
+    rate_window_ms = initial_window_ms_.Get();
+  bool is_small_sample = false;
+  float bitrate_sample_kbps = UpdateWindow(at_time.ms(), amount.bytes(),
+                                           rate_window_ms, &is_small_sample);
+  if (bitrate_sample_kbps < 0.0f)
+    return;
+  if (bitrate_estimate_kbps_ < 0.0f) {
+    // This is the very first sample we get. Use it to initialize the estimate.
+    bitrate_estimate_kbps_ = bitrate_sample_kbps;
+    return;
+  }
+  // Optionally use higher uncertainty for very small samples to avoid dropping
+  // estimate and for samples obtained in ALR.
+  float scale = uncertainty_scale_;
+  if (is_small_sample && bitrate_sample_kbps < bitrate_estimate_kbps_) {
+    scale = small_sample_uncertainty_scale_;
+  } else if (in_alr && bitrate_sample_kbps < bitrate_estimate_kbps_) {
+    // Optionally use higher uncertainty for samples obtained during ALR.
+    scale = uncertainty_scale_in_alr_;
+  }
+  // Define the sample uncertainty as a function of how far away it is from the
+  // current estimate. With low values of uncertainty_symmetry_cap_ we add more
+  // uncertainty to increases than to decreases. For higher values we approach
+  // symmetry.
+  float sample_uncertainty =
+      scale * std::abs(bitrate_estimate_kbps_ - bitrate_sample_kbps) /
+      (bitrate_estimate_kbps_ +
+       std::min(bitrate_sample_kbps,
+                uncertainty_symmetry_cap_.Get().kbps<float>()));
+
+  float sample_var = sample_uncertainty * sample_uncertainty;
+  // Update a bayesian estimate of the rate, weighting it lower if the sample
+  // uncertainty is large.
+  // The bitrate estimate uncertainty is increased with each update to model
+  // that the bitrate changes over time.
+  float pred_bitrate_estimate_var = bitrate_estimate_var_ + 5.f;
+  bitrate_estimate_kbps_ = (sample_var * bitrate_estimate_kbps_ +
+                            pred_bitrate_estimate_var * bitrate_sample_kbps) /
+                           (sample_var + pred_bitrate_estimate_var);
+  bitrate_estimate_kbps_ =
+      std::max(bitrate_estimate_kbps_, estimate_floor_.Get().kbps<float>());
+  bitrate_estimate_var_ = sample_var * pred_bitrate_estimate_var /
+                          (sample_var + pred_bitrate_estimate_var);
+  BWE_TEST_LOGGING_PLOT(1, "acknowledged_bitrate", at_time.ms(),
+                        bitrate_estimate_kbps_ * 1000);
+}
+
+float BitrateEstimator::UpdateWindow(int64_t now_ms,
+                                     int bytes,
+                                     int rate_window_ms,
+                                     bool* is_small_sample) {
+  RTC_DCHECK(is_small_sample != nullptr);
+  // Reset if time moves backwards.
+  if (now_ms < prev_time_ms_) {
+    prev_time_ms_ = -1;
+    sum_ = 0;
+    current_window_ms_ = 0;
+  }
+  if (prev_time_ms_ >= 0) {
+    current_window_ms_ += now_ms - prev_time_ms_;
+    // Reset if nothing has been received for more than a full window.
+    if (now_ms - prev_time_ms_ > rate_window_ms) {
+      sum_ = 0;
+      current_window_ms_ %= rate_window_ms;
+    }
+  }
+  prev_time_ms_ = now_ms;
+  float bitrate_sample = -1.0f;
+  if (current_window_ms_ >= rate_window_ms) {
+    *is_small_sample = sum_ < small_sample_threshold_->bytes();
+    bitrate_sample = 8.0f * sum_ / static_cast<float>(rate_window_ms);
+    current_window_ms_ -= rate_window_ms;
+    sum_ = 0;
+  }
+  sum_ += bytes;
+  return bitrate_sample;
+}
+
+absl::optional<DataRate> BitrateEstimator::bitrate() const {
+  if (bitrate_estimate_kbps_ < 0.f)
+    return absl::nullopt;
+  return DataRate::KilobitsPerSec(bitrate_estimate_kbps_);
+}
+
+absl::optional<DataRate> BitrateEstimator::PeekRate() const {
+  if (current_window_ms_ > 0)
+    return DataSize::Bytes(sum_) / TimeDelta::Millis(current_window_ms_);
+  return absl::nullopt;
+}
+
+void BitrateEstimator::ExpectFastRateChange() {
+  // By setting the bitrate-estimate variance to a higher value we allow the
+  // bitrate to change fast for the next few samples.
+  bitrate_estimate_var_ += 200;
+}
+
+}  // namespace webrtc