Improve bitrate probing for the audio-only case.

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 18 matching lines @@
 // The minimum probing duration in ms.
 constexpr int kMinProbeDurationMs = 15;
 
 // Maximum amount of time each probe can be delayed. Probe cluster is reset and
 // retried from the start when this limit is reached.
 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;
+
 }  // namespace
 
 BitrateProber::BitrateProber()
     : probing_state_(ProbingState::kDisabled),
       next_probe_time_ms_(-1),
       next_cluster_id_(0) {
   SetEnabled(true);
 }
 
 void BitrateProber::SetEnabled(bool enable) {
   if (enable) {
     if (probing_state_ == ProbingState::kDisabled) {
       probing_state_ = ProbingState::kInactive;
       LOG(LS_INFO) << "Bandwidth probing enabled, set to inactive";
     }
   } else {
     probing_state_ = ProbingState::kDisabled;
     LOG(LS_INFO) << "Bandwidth probing disabled";
   }
 }
 
 bool BitrateProber::IsProbing() const {
   return probing_state_ == ProbingState::kActive;
 }
 
 void BitrateProber::OnIncomingPacket(size_t packet_size) {
   // Don't initialize probing unless we have something large enough to start
   // probing.
-  if (probing_state_ == ProbingState::kInactive &&
-      !clusters_.empty() &&
-      packet_size >= PacedSender::kMinProbePacketSize) {
+  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) {
   RTC_DCHECK(probing_state_ != ProbingState::kDisabled);
   ProbeCluster cluster;
   cluster.min_probes = kMinProbePacketsSent;
@@ skipping 49 matching lines @@
   RTC_DCHECK(!clusters_.empty());
   RTC_DCHECK(ProbingState::kActive == probing_state_);
   return clusters_.front().id;
 }
 
 // Probe size is recommended based on the probe bitrate required. We choose
 // a minimum of twice |kMinProbeDeltaMs| interval to allow scheduling to be
 // feasible.
 size_t BitrateProber::RecommendedMinProbeSize() const {
   RTC_DCHECK(!clusters_.empty());
-  return clusters_.front().bitrate_bps * 2 * kMinProbeDeltaMs / (8 * 1000);
+  return clusters_.front().bitrate_bps * 3 * kMinProbeDeltaMs / (8 * 1000);
 }
 
 void BitrateProber::ProbeSent(int64_t now_ms, size_t bytes) {
   RTC_DCHECK(probing_state_ == ProbingState::kActive);
   RTC_DCHECK_GT(bytes, 0);
 
   if (!clusters_.empty()) {
     ProbeCluster* cluster = &clusters_.front();
     if (cluster->sent_probes == 0) {
       RTC_DCHECK_EQ(cluster->time_started_ms, -1);
@@ skipping 17 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