Add probing to recover faster from large bitrate drops.

webrtc/modules/congestion_controller/send_side_congestion_controller.cc

 /*
  *  Copyright (c) 2012 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.
  */
 
@@ skipping 265 matching lines @@
 void SendSideCongestionController::OnTransportFeedback(
     const rtcp::TransportFeedback& feedback) {
   RTC_DCHECK_RUNS_SERIALIZED(&worker_race_);
   transport_feedback_adapter_.OnTransportFeedback(feedback);
   std::vector<PacketFeedback> feedback_vector = ReceivedPacketFeedbackVector(
       transport_feedback_adapter_.GetTransportFeedbackVector());
   SortPacketFeedbackVector(&feedback_vector);
 
   bool currently_in_alr =
       pacer_->GetApplicationLimitedRegionStartTime().has_value();
-  if (!currently_in_alr && was_in_alr_) {
-    acknowledged_bitrate_estimator_->SetAlrEndedTimeMs(rtc::TimeMillis());
+  if (was_in_alr_ && !currently_in_alr) {
+    int64_t now_ms = rtc::TimeMillis();
+    acknowledged_bitrate_estimator_->SetAlrEndedTimeMs(now_ms);
+    probe_controller_->SetAlrEndedTimeMs(now_ms);
   }
   was_in_alr_ = currently_in_alr;
 
   acknowledged_bitrate_estimator_->IncomingPacketFeedbackVector(
       feedback_vector);
   DelayBasedBwe::Result result;
   {
     rtc::CritScope cs(&bwe_lock_);
     result = delay_based_bwe_->IncomingPacketFeedbackVector(
         feedback_vector, acknowledged_bitrate_estimator_->bitrate_bps());
   }
   if (result.updated)
     bitrate_controller_->OnDelayBasedBweResult(result);
+  if (result.suggested_probe_bps) {
+    probe_controller_->RequestProbe(*result.suggested_probe_bps);
+  }
 }
 
 std::vector<PacketFeedback>
 SendSideCongestionController::GetTransportFeedbackVector() const {
   RTC_DCHECK_RUNS_SERIALIZED(&worker_race_);
   return transport_feedback_adapter_.GetTransportFeedbackVector();
 }
 
 void SendSideCongestionController::MaybeTriggerOnNetworkChanged() {
   uint32_t bitrate_bps;
@@ skipping 47 matching lines @@
 bool SendSideCongestionController::IsSendQueueFull() const {
   return pacer_->ExpectedQueueTimeMs() > PacedSender::kMaxQueueLengthMs;
 }
 
 bool SendSideCongestionController::IsNetworkDown() const {
   rtc::CritScope cs(&network_state_lock_);
   return network_state_ == kNetworkDown;
 }
 
 }  // namespace webrtc