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Add field trial to cap trendline slope in delay-based BWE.

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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}
This commit is contained in:
Björn Terelius
2019-11-22 11:36:52 +01:00
committed by Commit Bot
parent efbda8d90a
commit 9281436650
2 changed files with 133 additions and 15 deletions
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112
modules/congestion_controller/goog_cc/trendline_estimator.cc
View File

@ -28,7 +28,6 @@ namespace webrtc {
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 @@ size_t ReadTrendlineFilterWindowSize(
}
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 @@ absl::optional<double> LinearFitSlope(
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 @@ constexpr int kDeltaCounterMax = 1000;
} // 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 @@ TrendlineEstimator::TrendlineEstimator(
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 @@ void TrendlineEstimator::UpdateTrendline(double recv_delta_ms,
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);

36
modules/congestion_controller/goog_cc/trendline_estimator.h
View File

@ -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 @@ class TrendlineEstimator : public DelayIncreaseDetectorInterface {
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 @@ class TrendlineEstimator : public DelayIncreaseDetectorInterface {
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.