Fix bug in BitrateProber where an old probe added at a high bitrate will stay active indefinit…

webrtc/modules/pacing/bitrate_prober.cc

 /*
  *  Copyright (c) 2014 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 23 matching lines @@
 constexpr int kMaxProbeDelayMs = 3;
 
 // Number of times probing is retried before the cluster is dropped.
 constexpr int kMaxRetryAttempts = 3;
 
 // The min probe packet size is scaled with the bitrate we're probing at.
 // This defines the max min probe packet size, meaning that on high bitrates
 // we have a min probe packet size of 200 bytes.
 constexpr size_t kMinProbePacketSize = 200;
 
+constexpr int64_t kProbeClusterTimeoutMs = 5000;
+
 }  // namespace
 
 BitrateProber::BitrateProber()
     : probing_state_(ProbingState::kDisabled),
       next_probe_time_ms_(-1),
       next_cluster_id_(0) {
   SetEnabled(true);
 }
 
 void BitrateProber::SetEnabled(bool enable) {
@@ skipping 17 matching lines @@
   // probing.
   if (probing_state_ == ProbingState::kInactive && !clusters_.empty() &&
       packet_size >=
           std::min<size_t>(RecommendedMinProbeSize(), kMinProbePacketSize)) {
     // Send next probe right away.
     next_probe_time_ms_ = -1;
     probing_state_ = ProbingState::kActive;
   }
 }
 
-void BitrateProber::CreateProbeCluster(int bitrate_bps) {
+void BitrateProber::CreateProbeCluster(int bitrate_bps, int64_t now_ms) {
   RTC_DCHECK(probing_state_ != ProbingState::kDisabled);
+  while (!clusters_.empty() &&
+         now_ms - clusters_.front().time_created_ms > kProbeClusterTimeoutMs) {
+    clusters_.pop();
+  }
+
   ProbeCluster cluster;
   cluster.min_probes = kMinProbePacketsSent;
   cluster.min_bytes = bitrate_bps * kMinProbeDurationMs / 8000;
   cluster.bitrate_bps = bitrate_bps;
+  cluster.time_created_ms = now_ms;
   cluster.id = next_cluster_id_++;
   clusters_.push(cluster);
 
   LOG(LS_INFO) << "Probe cluster (bitrate:min bytes:min packets): ("
                << cluster.bitrate_bps << ":" << cluster.min_bytes << ":"
                << cluster.min_probes << ")";
   // If we are already probing, continue to do so. Otherwise set it to
   // kInactive and wait for OnIncomingPacket to start the probing.
   if (probing_state_ != ProbingState::kActive)
     probing_state_ = ProbingState::kInactive;
 }
 
-void BitrateProber::ResetState() {
+void BitrateProber::ResetState(int64_t now_ms) {
   RTC_DCHECK(probing_state_ == ProbingState::kActive);
 
   // Recreate all probing clusters.
   std::queue<ProbeCluster> clusters;
   clusters.swap(clusters_);
   while (!clusters.empty()) {
     if (clusters.front().retries < kMaxRetryAttempts) {
-      CreateProbeCluster(clusters.front().bitrate_bps);
+      CreateProbeCluster(clusters.front().bitrate_bps, now_ms);
       clusters_.back().retries = clusters.front().retries + 1;
     }
     clusters.pop();
   }
 
   probing_state_ = ProbingState::kInactive;
 }
 
 int BitrateProber::TimeUntilNextProbe(int64_t now_ms) {
   // Probing is not active or probing is already complete.
   if (probing_state_ != ProbingState::kActive || clusters_.empty())
     return -1;
 
   int time_until_probe_ms = 0;
   if (next_probe_time_ms_ >= 0) {
     time_until_probe_ms = next_probe_time_ms_ - now_ms;
     if (time_until_probe_ms < -kMaxProbeDelayMs) {
-      ResetState();
+      ResetState(now_ms);
       return -1;
     }
   }
 
   return std::max(time_until_probe_ms, 0);
 }
 
 int BitrateProber::CurrentClusterId() const {
   RTC_DCHECK(!clusters_.empty());
   RTC_DCHECK(ProbingState::kActive == probing_state_);
@@ skipping 36 matching lines @@
 
   // Compute the time delta from the cluster start to ensure probe bitrate stays
   // close to the target bitrate. Result is in milliseconds.
   int64_t delta_ms = (8000ll * cluster.sent_bytes + cluster.bitrate_bps / 2) /
                   cluster.bitrate_bps;
   return cluster.time_started_ms + delta_ms;
 }
 
 
 }  // namespace webrtc