Improve bitrate probing for the audio-only case.

webrtc/modules/pacing/bitrate_prober.cc

Index: webrtc/modules/pacing/bitrate_prober.cc
diff --git a/webrtc/modules/pacing/bitrate_prober.cc b/webrtc/modules/pacing/bitrate_prober.cc
index bdf48fda1de5a793fb68f3545a16ba842f184c60..9d89df12436c73c066df3e77283c5c2ac13c55bf 100644
--- a/webrtc/modules/pacing/bitrate_prober.cc
+++ b/webrtc/modules/pacing/bitrate_prober.cc
@@ -64,9 +64,10 @@ bool BitrateProber::IsProbing() const {
 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) {
+  const size_t kMinProbePacketSize = 200;

[philipel, 2017/01/25 13:39:37]

Move to anonymous namespace. 

+  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;
@@ -136,7 +137,7 @@ int BitrateProber::CurrentClusterId() const {
 // 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) {