Add field trial to cap trendline slope in delay-based BWE.
Bug: webrtc:10932
Change-Id: I34a36a8cad16d65143eff9c675ee98bdbf176ace
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/160014
Reviewed-by: Christoffer Rodbro <crodbro@webrtc.org>
Commit-Queue: Björn Terelius <terelius@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#29872}
diff --git a/modules/congestion_controller/goog_cc/trendline_estimator.cc b/modules/congestion_controller/goog_cc/trendline_estimator.cc
index 8f4f133..6675a3b 100644
--- a/modules/congestion_controller/goog_cc/trendline_estimator.cc
+++ b/modules/congestion_controller/goog_cc/trendline_estimator.cc
@@ -28,7 +28,6 @@
namespace {
// Parameters for linear least squares fit of regression line to noisy data.
-constexpr size_t kDefaultTrendlineWindowSize = 20;
constexpr double kDefaultTrendlineSmoothingCoeff = 0.9;
constexpr double kDefaultTrendlineThresholdGain = 4.0;
const char kBweWindowSizeInPacketsExperiment[] =
@@ -48,7 +47,7 @@
}
RTC_LOG(LS_WARNING) << "Failed to parse parameters for BweWindowSizeInPackets"
" experiment from field trial string. Using default.";
- return kDefaultTrendlineWindowSize;
+ return TrendlineEstimatorSettings::kDefaultTrendlineWindowSize;
}
absl::optional<double> LinearFitSlope(
@@ -77,6 +76,34 @@
return numerator / denominator;
}
+absl::optional<double> ComputeSlopeCap(
+ const std::deque<TrendlineEstimator::PacketTiming>& packets,
+ const TrendlineEstimatorSettings& settings) {
+ RTC_DCHECK(1 <= settings.beginning_packets &&
+ settings.beginning_packets < packets.size());
+ RTC_DCHECK(1 <= settings.end_packets &&
+ settings.end_packets < packets.size());
+ RTC_DCHECK(settings.beginning_packets + settings.end_packets <=
+ packets.size());
+ TrendlineEstimator::PacketTiming early = packets[0];
+ for (size_t i = 1; i < settings.beginning_packets; ++i) {
+ if (packets[i].raw_delay_ms < early.raw_delay_ms)
+ early = packets[i];
+ }
+ size_t late_start = packets.size() - settings.end_packets;
+ TrendlineEstimator::PacketTiming late = packets[late_start];
+ for (size_t i = late_start + 1; i < packets.size(); ++i) {
+ if (packets[i].raw_delay_ms < late.raw_delay_ms)
+ late = packets[i];
+ }
+ if (late.arrival_time_ms - early.arrival_time_ms < 1) {
+ return absl::nullopt;
+ }
+ return (late.raw_delay_ms - early.raw_delay_ms) /
+ (late.arrival_time_ms - early.arrival_time_ms) +
+ settings.cap_uncertainty;
+}
+
constexpr double kMaxAdaptOffsetMs = 15.0;
constexpr double kOverUsingTimeThreshold = 10;
constexpr int kMinNumDeltas = 60;
@@ -84,13 +111,56 @@
} // namespace
+constexpr char TrendlineEstimatorSettings::kKey[];
+
+TrendlineEstimatorSettings::TrendlineEstimatorSettings(
+ const WebRtcKeyValueConfig* key_value_config) {
+ if (key_value_config->Lookup(kBweWindowSizeInPacketsExperiment)
+ .find("Enabled") == 0) {
+ window_size = ReadTrendlineFilterWindowSize(key_value_config);
+ }
+ Parser()->Parse(key_value_config->Lookup(TrendlineEstimatorSettings::kKey));
+ if (window_size < 10 || 200 < window_size) {
+ RTC_LOG(LS_WARNING) << "Window size must be between 10 and 200 packets";
+ window_size = kDefaultTrendlineWindowSize;
+ }
+ if (enable_cap) {
+ if (beginning_packets < 1 || end_packets < 1 ||
+ beginning_packets > window_size || end_packets > window_size) {
+ RTC_LOG(LS_WARNING) << "Size of beginning and end must be between 1 and "
+ << window_size;
+ enable_cap = false;
+ beginning_packets = end_packets = 0;
+ cap_uncertainty = 0.0;
+ }
+ if (beginning_packets + end_packets > window_size) {
+ RTC_LOG(LS_WARNING)
+ << "Size of beginning plus end can't exceed the window size";
+ enable_cap = false;
+ beginning_packets = end_packets = 0;
+ cap_uncertainty = 0.0;
+ }
+ if (cap_uncertainty < 0.0 || 0.025 < cap_uncertainty) {
+ RTC_LOG(LS_WARNING) << "Cap uncertainty must be between 0 and 0.025";
+ cap_uncertainty = 0.0;
+ }
+ }
+}
+
+std::unique_ptr<StructParametersParser> TrendlineEstimatorSettings::Parser() {
+ return StructParametersParser::Create("sort", &enable_sort, //
+ "cap", &enable_cap, //
+ "beginning_packets",
+ &beginning_packets, //
+ "end_packets", &end_packets, //
+ "cap_uncertainty", &cap_uncertainty, //
+ "window_size", &window_size);
+}
+
TrendlineEstimator::TrendlineEstimator(
const WebRtcKeyValueConfig* key_value_config,
NetworkStatePredictor* network_state_predictor)
- : window_size_(key_value_config->Lookup(kBweWindowSizeInPacketsExperiment)
- .find("Enabled") == 0
- ? ReadTrendlineFilterWindowSize(key_value_config)
- : kDefaultTrendlineWindowSize),
+ : settings_(key_value_config),
smoothing_coef_(kDefaultTrendlineSmoothingCoeff),
threshold_gain_(kDefaultTrendlineThresholdGain),
num_of_deltas_(0),
@@ -111,8 +181,8 @@
hypothesis_predicted_(BandwidthUsage::kBwNormal),
network_state_predictor_(network_state_predictor) {
RTC_LOG(LS_INFO)
- << "Using Trendline filter for delay change estimation with window size "
- << window_size_ << " and "
+ << "Using Trendline filter for delay change estimation with settings "
+ << settings_.Parser()->Encode() << " and "
<< (network_state_predictor_ ? "injected" : "no")
<< " network state predictor";
}
@@ -139,20 +209,38 @@
BWE_TEST_LOGGING_PLOT(1, "smoothed_delay_ms", arrival_time_ms,
smoothed_delay_);
- // Simple linear regression.
+ // Maintain packet window
delay_hist_.emplace_back(
static_cast<double>(arrival_time_ms - first_arrival_time_ms_),
- smoothed_delay_);
- if (delay_hist_.size() > window_size_)
+ smoothed_delay_, accumulated_delay_);
+ if (settings_.enable_sort) {
+ for (size_t i = delay_hist_.size() - 1;
+ i > 0 &&
+ delay_hist_[i].arrival_time_ms < delay_hist_[i - 1].arrival_time_ms;
+ --i) {
+ std::swap(delay_hist_[i], delay_hist_[i - 1]);
+ }
+ }
+ if (delay_hist_.size() > settings_.window_size)
delay_hist_.pop_front();
+
+ // Simple linear regression.
double trend = prev_trend_;
- if (delay_hist_.size() == window_size_) {
+ if (delay_hist_.size() == settings_.window_size) {
// Update trend_ if it is possible to fit a line to the data. The delay
// trend can be seen as an estimate of (send_rate - capacity)/capacity.
// 0 < trend < 1 -> the delay increases, queues are filling up
// trend == 0 -> the delay does not change
// trend < 0 -> the delay decreases, queues are being emptied
trend = LinearFitSlope(delay_hist_).value_or(trend);
+ if (settings_.enable_cap) {
+ absl::optional<double> cap = ComputeSlopeCap(delay_hist_, settings_);
+ // We only use the cap to filter out overuse detections, not
+ // to detect additional underuses.
+ if (trend >= 0 && cap.has_value() && trend > cap.value()) {
+ trend = cap.value();
+ }
+ }
}
BWE_TEST_LOGGING_PLOT(1, "trendline_slope", arrival_time_ms, trend);
diff --git a/modules/congestion_controller/goog_cc/trendline_estimator.h b/modules/congestion_controller/goog_cc/trendline_estimator.h
index 5bec23b..2db2903 100644
--- a/modules/congestion_controller/goog_cc/trendline_estimator.h
+++ b/modules/congestion_controller/goog_cc/trendline_estimator.h
@@ -22,9 +22,35 @@
#include "modules/congestion_controller/goog_cc/delay_increase_detector_interface.h"
#include "modules/remote_bitrate_estimator/include/bwe_defines.h"
#include "rtc_base/constructor_magic.h"
+#include "rtc_base/experiments/struct_parameters_parser.h"
namespace webrtc {
+struct TrendlineEstimatorSettings {
+ static constexpr char kKey[] = "WebRTC-Bwe-TrendlineEstimatorSettings";
+ static constexpr unsigned kDefaultTrendlineWindowSize = 20;
+
+ TrendlineEstimatorSettings() = delete;
+ explicit TrendlineEstimatorSettings(
+ const WebRtcKeyValueConfig* key_value_config);
+
+ // Sort the packets in the window. Should be redundant,
+ // but then almost no cost.
+ bool enable_sort = false;
+
+ // Cap the trendline slope based on the minimum delay seen
+ // in the beginning_packets and end_packets respectively.
+ bool enable_cap = false;
+ unsigned beginning_packets = 7;
+ unsigned end_packets = 7;
+ double cap_uncertainty = 0.0;
+
+ // Size (in packets) of the window.
+ unsigned window_size = kDefaultTrendlineWindowSize;
+
+ std::unique_ptr<StructParametersParser> Parser();
+};
+
class TrendlineEstimator : public DelayIncreaseDetectorInterface {
public:
TrendlineEstimator(const WebRtcKeyValueConfig* key_value_config,
@@ -50,11 +76,15 @@
BandwidthUsage State() const override;
struct PacketTiming {
- PacketTiming(double arrival_time_ms, double smoothed_delay_ms)
+ PacketTiming(double arrival_time_ms,
+ double smoothed_delay_ms,
+ double raw_delay_ms)
: arrival_time_ms(arrival_time_ms),
- smoothed_delay_ms(smoothed_delay_ms) {}
+ smoothed_delay_ms(smoothed_delay_ms),
+ raw_delay_ms(raw_delay_ms) {}
double arrival_time_ms;
double smoothed_delay_ms;
+ double raw_delay_ms;
};
private:
@@ -64,7 +94,7 @@
void UpdateThreshold(double modified_offset, int64_t now_ms);
// Parameters.
- const size_t window_size_;
+ TrendlineEstimatorSettings settings_;
const double smoothing_coef_;
const double threshold_gain_;
// Used by the existing threshold.