Initiate mid-call probing even if estimated bitrate is at max configured bitrate.

webrtc/modules/congestion_controller/probe_controller.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.
  */
 
@@ skipping 54 matching lines @@
                                   int64_t start_bitrate_bps,
                                   int64_t max_bitrate_bps) {
   rtc::CritScope cs(&critsect_);
 
   if (start_bitrate_bps > 0)  {
     start_bitrate_bps_ = start_bitrate_bps;
   } else if (start_bitrate_bps_ == 0) {
     start_bitrate_bps_ = min_bitrate_bps;
   }
 
+  // The reason we use the variable |old_max_bitrate_pbs| is because we
+  // need to set |max_bitrate_bps_| before we call InitiateProbing.
   int64_t old_max_bitrate_bps = max_bitrate_bps_;
   max_bitrate_bps_ = max_bitrate_bps;
 
   switch (state_) {
     case State::kInit:
       if (network_state_ == kNetworkUp)
         InitiateExponentialProbing();
       break;
 
     case State::kWaitingForProbingResult:
       break;
 
     case State::kProbingComplete:
-      // Initiate probing when |max_bitrate_| was increased mid-call.
-      if (estimated_bitrate_bps_ != kExponentialProbingDisabled &&
-          estimated_bitrate_bps_ < old_max_bitrate_bps &&
-          max_bitrate_bps_ > old_max_bitrate_bps) {
+      // If the new max bitrate is higher than the old max bitrate and the
+      // estimate is lower than the new max bitrate then initiate probing.
+      if (estimated_bitrate_bps_ != 0 &&
+          old_max_bitrate_bps < max_bitrate_bps_ &&
+          estimated_bitrate_bps_ < max_bitrate_bps_) {
         // The assumption is that if we jump more than 20% in the bandwidth
         // estimate or if the bandwidth estimate is within 90% of the new
         // max bitrate then the probing attempt was successful.
         mid_call_probing_succcess_threshold_ =
             std::min(estimated_bitrate_bps_ * 1.2, max_bitrate_bps_ * 0.9);
         mid_call_probing_waiting_for_result_ = true;
         mid_call_probing_bitrate_bps_ = max_bitrate_bps_;
 
         RTC_HISTOGRAM_COUNTS_10000("WebRTC.BWE.MidCallProbing.Initiated",
                                    max_bitrate_bps_ / 1000);
@@ skipping 131 matching lines @@
     state_ = State::kWaitingForProbingResult;
     min_bitrate_to_probe_further_bps_ =
         (*(bitrates_to_probe.end() - 1)) * kRepeatedProbeMinPercentage / 100;
   } else {
     state_ = State::kProbingComplete;
     min_bitrate_to_probe_further_bps_ = kExponentialProbingDisabled;
   }
 }
 
 }  // namespace webrtc