Fix issue where the first audio packets significantly impacts initial BWE negatively.

webrtc/modules/remote_bitrate_estimator/remote_bitrate_estimator_abs_send_time.cc

 /*
  *  Copyright (c) 2013 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 79 matching lines @@
       RemoteBitrateObserver* observer,
       Clock* clock,
       uint32_t min_bitrate_bps)
       : crit_sect_(CriticalSectionWrapper::CreateCriticalSection()),
         observer_(observer),
         clock_(clock),
         ssrcs_(),
         inter_arrival_(),
         estimator_(OverUseDetectorOptions()),
         detector_(OverUseDetectorOptions()),
-        incoming_bitrate_(1000, 8000),
+        incoming_bitrate_(kBitrateWindowMs, 8000),
         remote_rate_(min_bitrate_bps),
         last_process_time_(-1),
         process_interval_ms_(kProcessIntervalMs),
         total_propagation_delta_ms_(0),
         total_probes_received_(0),
         first_packet_time_ms_(-1) {
   assert(observer_);
   assert(clock_);
   LOG(LS_INFO) << "RemoteBitrateEstimatorAbsSendTime: Instantiating.";
 }
@@ skipping 70 matching lines @@
     // we will remove the oldest one.
     if (probes_.size() >= kMaxProbePackets)
       probes_.pop_front();
     return;
   }
 
   std::list<Cluster>::const_iterator best_it = FindBestProbe(clusters);
   if (best_it != clusters.end()) {
     int probe_bitrate_bps =
         std::min(best_it->GetSendBitrateBps(), best_it->GetRecvBitrateBps());
-    if (IsBitrateImproving(probe_bitrate_bps)) {
+    // Make sure that a probe sent on a lower bitrate than our estimate can't
+    // reduce the estimate.
+    if (IsBitrateImproving(probe_bitrate_bps) &&
+        probe_bitrate_bps > static_cast<int>(incoming_bitrate_.Rate(now_ms))) {
       LOG(LS_INFO) << "Probe successful, sent at "
                    << best_it->GetSendBitrateBps() << " bps, received at "
                    << best_it->GetRecvBitrateBps()
                    << " bps. Mean send delta: " << best_it->send_mean_ms
                    << " ms, mean recv delta: " << best_it->recv_mean_ms
                    << " ms, num probes: " << best_it->count;
       remote_rate_.SetEstimate(probe_bitrate_bps, now_ms);
     }
   }
 
@@ skipping 221 matching lines @@
 
   RemoveStaleEntries(
       &recent_update_time_ms_,
       &recent_propagation_delta_ms_,
       now_ms - kPropagationDeltaQueueMaxTimeMs);
 
   total_propagation_delta_ms_ =
       std::max(total_propagation_delta_ms_ + propagation_delta_ms, 0);
 }
 }  // namespace webrtc