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Add loss-based BWE experiment which allows us to try different parameters.

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BUG=webrtc:5839
R=terelius@webrtc.org

Review-Url: https://codereview.webrtc.org/2786353002 .
Cr-Commit-Position: refs/heads/master@{#17490}
This commit is contained in:
Stefan Holmer
2017-03-31 15:53:27 +02:00
parent fdbfdc9786
commit 9c79ed9224
2 changed files with 94 additions and 18 deletions
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109
webrtc/modules/bitrate_controller/send_side_bandwidth_estimation.cc
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@ -12,6 +12,8 @@
#include <algorithm>
#include <cmath>
#include <limits>
#include <string>
#include "webrtc/base/checks.h"
#include "webrtc/base/logging.h"
@ -35,6 +37,10 @@ const int64_t kFeedbackIntervalMs = 1500;
const int64_t kFeedbackTimeoutIntervals = 3;
const int64_t kTimeoutIntervalMs = 1000;
const float kDefaultLowLossThreshold = 0.02f;
const float kDefaultHighLossThreshold = 0.1f;
const int kDefaultBitrateThresholdKbps = 0;
struct UmaRampUpMetric {
const char* metric_name;
int bitrate_kbps;
@ -47,6 +53,52 @@ const UmaRampUpMetric kUmaRampupMetrics[] = {
const size_t kNumUmaRampupMetrics =
sizeof(kUmaRampupMetrics) / sizeof(kUmaRampupMetrics[0]);
const char kBweLosExperiment[] = "WebRTC-BweLossExperiment";
bool BweLossExperimentIsEnabled() {
std::string experiment_string =
webrtc::field_trial::FindFullName(kBweLosExperiment);
// The experiment is enabled iff the field trial string begins with "Enabled".
return experiment_string.find("Enabled") == 0;
}
bool ReadBweLossExperimentParameters(float* low_loss_threshold,
float* high_loss_threshold,
uint32_t* bitrate_threshold_kbps) {
RTC_DCHECK(low_loss_threshold);
RTC_DCHECK(high_loss_threshold);
RTC_DCHECK(bitrate_threshold_kbps);
std::string experiment_string =
webrtc::field_trial::FindFullName(kBweLosExperiment);
int parsed_values =
sscanf(experiment_string.c_str(), "Enabled-%f,%f,%u", low_loss_threshold,
high_loss_threshold, bitrate_threshold_kbps);
if (parsed_values == 3) {
RTC_CHECK_GT(*low_loss_threshold, 0.0f)
<< "Loss threshold must be greater than 0.";
RTC_CHECK_LE(*low_loss_threshold, 1.0f)
<< "Loss threshold must be less than or equal to 1.";
RTC_CHECK_GT(*high_loss_threshold, 0.0f)
<< "Loss threshold must be greater than 0.";
RTC_CHECK_LE(*high_loss_threshold, 1.0f)
<< "Loss threshold must be less than or equal to 1.";
RTC_CHECK_LE(*low_loss_threshold, *high_loss_threshold)
<< "The low loss threshold must be less than or equal to the high loss "
"threshold.";
RTC_CHECK_GE(*bitrate_threshold_kbps, 0)
<< "Bitrate threshold can't be negative.";
RTC_CHECK_LT(*bitrate_threshold_kbps,
std::numeric_limits<int>::max() / 1000)
<< "Bitrate must be smaller enough to avoid overflows.";
return true;
}
LOG(LS_WARNING) << "Failed to parse parameters for BweLossExperiment "
"experiment from field trial string. Using default.";
*low_loss_threshold = kDefaultLowLossThreshold;
*high_loss_threshold = kDefaultHighLossThreshold;
*bitrate_threshold_kbps = kDefaultBitrateThresholdKbps;
return false;
}
} // namespace
SendSideBandwidthEstimation::SendSideBandwidthEstimation(RtcEventLog* event_log)
@ -74,8 +126,22 @@ SendSideBandwidthEstimation::SendSideBandwidthEstimation(RtcEventLog* event_log)
event_log_(event_log),
last_rtc_event_log_ms_(-1),
in_timeout_experiment_(
webrtc::field_trial::IsEnabled("WebRTC-FeedbackTimeout")) {
webrtc::field_trial::IsEnabled("WebRTC-FeedbackTimeout")),
low_loss_threshold_(kDefaultLowLossThreshold),
high_loss_threshold_(kDefaultHighLossThreshold),
bitrate_threshold_bps_(1000 * kDefaultBitrateThresholdKbps) {
RTC_DCHECK(event_log);
if (BweLossExperimentIsEnabled()) {
uint32_t bitrate_threshold_kbps;
if (ReadBweLossExperimentParameters(&low_loss_threshold_,
&high_loss_threshold_,
&bitrate_threshold_kbps)) {
LOG(LS_INFO) << "Enabled BweLossExperiment with parameters "
<< low_loss_threshold_ << ", " << high_loss_threshold_
<< ", " << bitrate_threshold_kbps;
bitrate_threshold_bps_ = bitrate_threshold_kbps * 1000;
}
}
}
SendSideBandwidthEstimation::~SendSideBandwidthEstimation() {}
@ -229,7 +295,12 @@ void SendSideBandwidthEstimation::UpdateEstimate(int64_t now_ms) {
int64_t time_since_packet_report_ms = now_ms - last_packet_report_ms_;
int64_t time_since_feedback_ms = now_ms - last_feedback_ms_;
if (time_since_packet_report_ms < 1.2 * kFeedbackIntervalMs) {
if (last_fraction_loss_ <= 5) {
// We only care about loss above a given bitrate threshold.
float loss = last_fraction_loss_ / 256.0f;
// We only make decisions based on loss when the bitrate is above a
// threshold. This is a crude way of handling loss which is uncorrelated
// to congestion.
if (bitrate_ < bitrate_threshold_bps_ || loss <= low_loss_threshold_) {
// Loss < 2%: Increase rate by 8% of the min bitrate in the last
// kBweIncreaseIntervalMs.
// Note that by remembering the bitrate over the last second one can
@ -247,23 +318,25 @@ void SendSideBandwidthEstimation::UpdateEstimate(int64_t now_ms) {
// (gives a little extra increase at low rates, negligible at higher
// rates).
bitrate_ += 1000;
} else if (last_fraction_loss_ <= 26) {
// Loss between 2% - 10%: Do nothing.
} else {
// Loss > 10%: Limit the rate decreases to once a kBweDecreaseIntervalMs
// + rtt.
if (!has_decreased_since_last_fraction_loss_ &&
(now_ms - time_last_decrease_ms_) >=
(kBweDecreaseIntervalMs + last_round_trip_time_ms_)) {
time_last_decrease_ms_ = now_ms;
} else if (bitrate_ > bitrate_threshold_bps_) {
if (loss <= high_loss_threshold_) {
// Loss between 2% - 10%: Do nothing.
} else {
// Loss > 10%: Limit the rate decreases to once a kBweDecreaseIntervalMs
// + rtt.
if (!has_decreased_since_last_fraction_loss_ &&
(now_ms - time_last_decrease_ms_) >=
(kBweDecreaseIntervalMs + last_round_trip_time_ms_)) {
time_last_decrease_ms_ = now_ms;
// Reduce rate:
// newRate = rate * (1 - 0.5*lossRate);
// where packetLoss = 256*lossRate;
bitrate_ = static_cast<uint32_t>(
(bitrate_ * static_cast<double>(512 - last_fraction_loss_)) /
512.0);
has_decreased_since_last_fraction_loss_ = true;
// Reduce rate:
// newRate = rate * (1 - 0.5*lossRate);
// where packetLoss = 256*lossRate;
bitrate_ = static_cast<uint32_t>(
(bitrate_ * static_cast<double>(512 - last_fraction_loss_)) /
512.0);
has_decreased_since_last_fraction_loss_ = true;
}
}
}
} else if (time_since_feedback_ms >