Wire up experiment for improved screenshare bwe.

webrtc/modules/pacing/alr_detector.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/pacing/alr_detector.h"
 
+#include <string>
+
 #include "webrtc/base/checks.h"
 #include "webrtc/base/logging.h"
+#include "webrtc/system_wrappers/include/field_trial.h"
 
 namespace {
-
 // Time period over which outgoing traffic is measured.
 constexpr int kMeasurementPeriodMs = 500;
 
-// Sent traffic percentage as a function of network capacity used to determine
-// application-limited region. ALR region start when bandwidth usage drops below
-// kAlrStartUsagePercent and ends when it raises above kAlrEndUsagePercent.
-// NOTE: This is intentionally conservative at the moment until BW adjustments
-// of application limited region is fine tuned.
-constexpr int kAlrStartUsagePercent = 60;
-constexpr int kAlrEndUsagePercent = 70;
-
 }  // namespace
 
 namespace webrtc {
 
+const char* AlrDetector::kScreenshareProbingBweExperimentName =
+    "WebRTC-ProbingScreenshareBwe";
+
 AlrDetector::AlrDetector()
-    : rate_(kMeasurementPeriodMs, RateStatistics::kBpsScale) {}
+    : alr_start_usage_percent_(kDefaultAlrStartUsagePercent),
+      alr_end_usage_percent_(kDefaultAlrEndUsagePercent),
+      rate_(kMeasurementPeriodMs, RateStatistics::kBpsScale),
+      estimated_bitrate_bps_(0) {
+  rtc::Optional<AlrExperimentSettings> experiment_settings =
+      ParseAlrSettingsFromFieldTrial();
+  if (experiment_settings) {
+    alr_start_usage_percent_ = experiment_settings->alr_start_usage_percent;
+    alr_end_usage_percent_ = experiment_settings->alr_end_usage_percent;
+  }
+}
 
 AlrDetector::~AlrDetector() {}
 
 void AlrDetector::OnBytesSent(size_t bytes_sent, int64_t now_ms) {
   RTC_DCHECK(estimated_bitrate_bps_);
 
   rate_.Update(bytes_sent, now_ms);
   rtc::Optional<uint32_t> rate = rate_.Rate(now_ms);
   if (!rate)
     return;
 
   int percentage = static_cast<int>(*rate) * 100 / estimated_bitrate_bps_;
-  if (percentage < kAlrStartUsagePercent && !alr_started_time_ms_) {
+  if (percentage < alr_start_usage_percent_ && !alr_started_time_ms_) {
     alr_started_time_ms_ = rtc::Optional<int64_t>(now_ms);
-  } else if (percentage > kAlrEndUsagePercent && alr_started_time_ms_) {
+  } else if (percentage > alr_end_usage_percent_ && alr_started_time_ms_) {
     alr_started_time_ms_ = rtc::Optional<int64_t>();
   }
 }
 
 void AlrDetector::SetEstimatedBitrate(int bitrate_bps) {
   RTC_DCHECK(bitrate_bps);
   estimated_bitrate_bps_ = bitrate_bps;
 }
 
 rtc::Optional<int64_t> AlrDetector::GetApplicationLimitedRegionStartTime()
     const {
   return alr_started_time_ms_;
 }
 
+rtc::Optional<AlrDetector::AlrExperimentSettings>
+AlrDetector::ParseAlrSettingsFromFieldTrial() {
+  rtc::Optional<AlrExperimentSettings> ret;
+  std::string group_name =
+      field_trial::FindFullName(kScreenshareProbingBweExperimentName);
+
+  const std::string kIgnoredSuffix = "_Dogfood";
+  if (group_name.rfind(kIgnoredSuffix) ==
+      group_name.length() - kIgnoredSuffix.length()) {
+    group_name.resize(group_name.length() - kIgnoredSuffix.length());
+  }
+
+  if (group_name.empty())
+    return ret;
+
+  AlrExperimentSettings settings;
+  if (sscanf(group_name.c_str(), "%f-%ld-%d-%d", &settings.pacing_factor,
+             &settings.max_paced_queue_time, &settings.alr_start_usage_percent,
+             &settings.alr_end_usage_percent) == 4) {
+    ret.emplace(settings);
+    LOG(LS_INFO) << "Using screenshare ALR experiment settings: "
+                    "pacing factor: "
+                 << settings.pacing_factor << ", max pacer queue length: "
+                 << settings.max_paced_queue_time
+                 << ", ALR start usage percent: "
+                 << settings.alr_start_usage_percent
+                 << ", ALR end usage percent: "
+                 << settings.alr_end_usage_percent;
+  }
+
+  return ret;
+}
+
 }  // namespace webrtc