Let alr dectector use a budged to detect underuse.

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/format_macros.h"
 #include "webrtc/base/logging.h"
+#include "webrtc/base/timeutils.h"
 #include "webrtc/system_wrappers/include/field_trial.h"
 
-namespace {
-// Time period over which outgoing traffic is measured.
-constexpr int kMeasurementPeriodMs = 500;
-
-}  // namespace
-
 namespace webrtc {
 
 const char* AlrDetector::kScreenshareProbingBweExperimentName =
     "WebRTC-ProbingScreenshareBwe";
 
 AlrDetector::AlrDetector()
-    : alr_start_usage_percent_(kDefaultAlrStartUsagePercent),
-      alr_end_usage_percent_(kDefaultAlrEndUsagePercent),
-      rate_(kMeasurementPeriodMs, RateStatistics::kBpsScale),
-      estimated_bitrate_bps_(0) {
+    : bandwidth_usage_percent_(kDefaultAlrBandwidthUsagePercent),
+      alr_start_budget_level_percent_(kDefaultAlrStartBudgetLevelPercent),
+      alr_stop_budget_level_percent_(kDefaultAlrStopBudgetLevelPercent),
+      alr_budget_(0, true) {
   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;
+    alr_stop_budget_level_percent_ =
+        experiment_settings->alr_stop_budget_level_percent;
+    alr_start_budget_level_percent_ =
+        experiment_settings->alr_start_budget_level_percent;
+    bandwidth_usage_percent_ = experiment_settings->alr_bandwidth_usage_percent;
   }
 }
 
 AlrDetector::~AlrDetector() {}
 
-void AlrDetector::OnBytesSent(size_t bytes_sent, int64_t now_ms) {
-  RTC_DCHECK(estimated_bitrate_bps_);
+void AlrDetector::OnBytesSent(size_t bytes_sent, int64_t delta_time_ms) {
+  alr_budget_.UseBudget(bytes_sent);
+  alr_budget_.IncreaseBudget(delta_time_ms);

[philipel, 2017/07/10 11:41:05]

Not sure if it matters, but wont calling UseBudget and then IncreaseBudget cause
a bias to exit ALR somewhat quicker than entering it?

[tschumi, 2017/07/11 09:33:31]

I could do it the other way around but then we would have a bias on entering
ALR.

 
-  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 < alr_start_usage_percent_ && !alr_started_time_ms_) {
-    alr_started_time_ms_ = rtc::Optional<int64_t>(now_ms);
-  } else if (percentage > alr_end_usage_percent_ && alr_started_time_ms_) {
+  if (alr_budget_.budget_level_percent() > alr_start_budget_level_percent_ &&
+      !alr_started_time_ms_) {
+    alr_started_time_ms_ = rtc::Optional<int64_t>(rtc::TimeMillis());

[philipel, 2017/07/10 11:41:05]

Nit:
alr_start_time_ms_.emplace(rtc::TimeMillis());

[tschumi, 2017/07/11 09:33:31]

Done.

+  } else if (alr_budget_.budget_level_percent() <
+                 alr_stop_budget_level_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;
+  alr_budget_.set_target_rate_kbps(bitrate_bps * bandwidth_usage_percent_ /
+                                   (1000 * 100));
 }
 
 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-%" PRId64 "-%d-%d",
+  if (sscanf(group_name.c_str(), "%f,%" PRId64 ",%d,%d,%d",
              &settings.pacing_factor, &settings.max_paced_queue_time,
-             &settings.alr_start_usage_percent,
-             &settings.alr_end_usage_percent) == 4) {
+             &settings.alr_bandwidth_usage_percent,
+             &settings.alr_start_budget_level_percent,
+             &settings.alr_stop_budget_level_percent) == 5) {
     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;
+                 << ", ALR start bandwidth usage percent: "
+                 << settings.alr_bandwidth_usage_percent
+                 << ", ALR end budget level percent: "
+                 << settings.alr_start_budget_level_percent
+                 << ", ALR end budget level percent: "
+                 << settings.alr_stop_budget_level_percent;
   }
 
   return ret;
 }
 
 }  // namespace webrtc