BitrateProber: Support higher probing bitrates

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.
  */
 
 #include "webrtc/modules/pacing/bitrate_prober.h"
 
 #include <algorithm>
 
 #include "webrtc/base/checks.h"
 #include "webrtc/base/logging.h"
 #include "webrtc/modules/pacing/paced_sender.h"
 
 namespace webrtc {
 
 namespace {
 
 // Inactivity threshold above which probing is restarted.
 constexpr int kInactivityThresholdMs = 5000;
 
-int ComputeDeltaFromBitrate(size_t packet_size, uint32_t bitrate_bps) {
+// A minimum interval between probes to allow scheduling to be feasible.
+constexpr int kMinProbeDeltaMs = 1;
+
+int ComputeDeltaFromBitrate(size_t probe_size, uint32_t bitrate_bps) {
   RTC_CHECK_GT(bitrate_bps, 0u);
-  // Compute the time delta needed to send packet_size bytes at bitrate_bps
+  // Compute the time delta needed to send probe_size bytes at bitrate_bps
   // bps. Result is in milliseconds.
-  return static_cast<int>((1000ll * packet_size * 8) / bitrate_bps);
+  return static_cast<int>((1000ll * probe_size * 8) / bitrate_bps);
 }
 }  // namespace
 
 BitrateProber::BitrateProber()
     : probing_state_(ProbingState::kDisabled),
-      packet_size_last_sent_(0),
+      probe_size_last_sent_(0),
       time_last_probe_sent_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";
@@ skipping 11 matching lines @@
 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) {
     probing_state_ = ProbingState::kActive;
   }
 }
 
-void BitrateProber::CreateProbeCluster(int bitrate_bps, int num_packets) {
+void BitrateProber::CreateProbeCluster(int bitrate_bps, int num_probes) {
   RTC_DCHECK(probing_state_ != ProbingState::kDisabled);
   ProbeCluster cluster;
-  cluster.max_probe_packets = num_packets;
+  cluster.max_probes = num_probes;
   cluster.probe_bitrate_bps = bitrate_bps;
   cluster.id = next_cluster_id_++;
   clusters_.push(cluster);
-  LOG(LS_INFO) << "Probe cluster (bitrate:packets): ("
-               << cluster.probe_bitrate_bps << ":" << cluster.max_probe_packets
+  LOG(LS_INFO) << "Probe cluster (bitrate:probes): ("
+               << cluster.probe_bitrate_bps << ":" << cluster.max_probes
                << ") ";
   if (probing_state_ != ProbingState::kActive)
     probing_state_ = ProbingState::kInactive;
 }
 
 void BitrateProber::ResetState() {
   time_last_probe_sent_ms_ = -1;
-  packet_size_last_sent_ = 0;
+  probe_size_last_sent_ = 0;
 
   // Recreate all probing clusters.
   std::queue<ProbeCluster> clusters;
   clusters.swap(clusters_);
   while (!clusters.empty()) {
     CreateProbeCluster(clusters.front().probe_bitrate_bps,
-                       clusters.front().max_probe_packets);
+                       clusters.front().max_probes);
     clusters.pop();
   }
   // If its enabled, reset to inactive.
   if (probing_state_ != ProbingState::kDisabled)
     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;
   // time_last_probe_sent_ms_ of -1 indicates no probes have yet been sent.
   int64_t elapsed_time_ms;
   if (time_last_probe_sent_ms_ == -1) {
     elapsed_time_ms = 0;
   } else {
     elapsed_time_ms = now_ms - time_last_probe_sent_ms_;
   }
   // If no probes have been sent for a while, abort current probing and
   // reset.
   if (elapsed_time_ms > kInactivityThresholdMs) {
     ResetState();
     return -1;
   }
   // We will send the first probe packet immediately if no packet has been
   // sent before.
   int time_until_probe_ms = 0;
-  if (packet_size_last_sent_ != 0 && probing_state_ == ProbingState::kActive) {
+  if (probe_size_last_sent_ != 0 && probing_state_ == ProbingState::kActive) {
     int next_delta_ms = ComputeDeltaFromBitrate(
-        packet_size_last_sent_, clusters_.front().probe_bitrate_bps);
+        probe_size_last_sent_, clusters_.front().probe_bitrate_bps);
     time_until_probe_ms = next_delta_ms - elapsed_time_ms;
-    // There is no point in trying to probe with less than 1 ms between packets
-    // as it essentially means trying to probe at infinite bandwidth.
-    const int kMinProbeDeltaMs = 1;
     // If we have waited more than 3 ms for a new packet to probe with we will
     // consider this probing session over.
     const int kMaxProbeDelayMs = 3;
     if (next_delta_ms < kMinProbeDeltaMs ||
         time_until_probe_ms < -kMaxProbeDelayMs) {
       probing_state_ = ProbingState::kSuspended;
       LOG(LS_INFO) << "Delta too small or missed probing accurately, suspend";
       time_until_probe_ms = 0;
     }
   }
   return std::max(time_until_probe_ms, 0);
 }
 
 int BitrateProber::CurrentClusterId() const {
   RTC_DCHECK(!clusters_.empty());
   RTC_DCHECK(ProbingState::kActive == probing_state_);
   return clusters_.front().id;
 }
 
-size_t BitrateProber::RecommendedPacketSize() const {
-  return packet_size_last_sent_;
+// 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::RecommendedProbeSize() const {

[stefan-webrtc, 2016/09/16 07:42:53]

Isn't this the recommended minimum size? Larger sizes are still ok, and perhaps
even recommended, right?

[Irfan, 2016/09/19 06:05:11]

Right, updated to reflect that.

+  RTC_DCHECK(!clusters_.empty());
+  return clusters_.front().probe_bitrate_bps * 2 * kMinProbeDeltaMs /
+         (8 * 1000);
 }
 
-void BitrateProber::PacketSent(int64_t now_ms, size_t packet_size) {
-  assert(packet_size > 0);
-  if (packet_size < PacedSender::kMinProbePacketSize)
-    return;
-  packet_size_last_sent_ = packet_size;
-  if (probing_state_ != ProbingState::kActive)
-    return;
+void BitrateProber::ProbeSent(int64_t now_ms, size_t bytes) {
+  RTC_DCHECK(probing_state_ == ProbingState::kActive);

[stefan-webrtc, 2016/09/16 07:42:53]

DCHECK_EQ

[Irfan, 2016/09/19 06:05:11]

DCHECK_EQ does not work on scoped enums

[stefan-webrtc, 2016/09/19 07:24:56]

Acknowledged.

+  assert(bytes > 0);

[stefan-webrtc, 2016/09/16 07:42:53]

RTC_DCHECK_GT

[Irfan, 2016/09/19 06:05:11]

This assert is actually redundant given it is an unsigned type. Removed.

[stefan-webrtc, 2016/09/19 07:24:55]

Is 0 not still possible?

[Irfan, 2016/09/19 18:23:30]

Ah yes, added

+  probe_size_last_sent_ = bytes;
   time_last_probe_sent_ms_ = now_ms;
   if (!clusters_.empty()) {
     ProbeCluster* cluster = &clusters_.front();
-    ++cluster->sent_probe_packets;
-    if (cluster->sent_probe_packets == cluster->max_probe_packets)
+    ++cluster->sent_probes;
+    if (cluster->sent_probes == cluster->max_probes)
       clusters_.pop();
     if (clusters_.empty())
       probing_state_ = ProbingState::kSuspended;
   }
 }
 }  // namespace webrtc