1 files changed, 204 insertions, 0 deletions
diff --git a/third_party/libwebrtc/modules/pacing/bitrate_prober.cc b/third_party/libwebrtc/modules/pacing/bitrate_prober.cc
new file mode 100644
index 0000000000..ec9182fca2
--- /dev/null
+++ b/third_party/libwebrtc/modules/pacing/bitrate_prober.cc
@@ -0,0 +1,204 @@
+/*
+ *  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 "modules/pacing/bitrate_prober.h"
+
+#include <algorithm>
+
+#include "absl/memory/memory.h"
+#include "api/rtc_event_log/rtc_event.h"
+#include "api/rtc_event_log/rtc_event_log.h"
+#include "logging/rtc_event_log/events/rtc_event_probe_cluster_created.h"
+#include "rtc_base/checks.h"
+#include "rtc_base/logging.h"
+#include "system_wrappers/include/metrics.h"
+
+namespace webrtc {
+
+namespace {
+// 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 DataSize kMinProbePacketSize = DataSize::Bytes(200);
+
+constexpr TimeDelta kProbeClusterTimeout = TimeDelta::Seconds(5);
+
+}  // namespace
+
+BitrateProberConfig::BitrateProberConfig(
+    const FieldTrialsView* key_value_config)
+    : min_probe_delta("min_probe_delta", TimeDelta::Millis(1)),
+      max_probe_delay("max_probe_delay", TimeDelta::Millis(10)) {
+  ParseFieldTrial({&min_probe_delta, &max_probe_delay},
+                  key_value_config->Lookup("WebRTC-Bwe-ProbingBehavior"));
+}
+
+BitrateProber::~BitrateProber() {
+  RTC_HISTOGRAM_COUNTS_1000("WebRTC.BWE.Probing.TotalProbeClustersRequested",
+                            total_probe_count_);
+  RTC_HISTOGRAM_COUNTS_1000("WebRTC.BWE.Probing.TotalFailedProbeClusters",
+                            total_failed_probe_count_);
+}
+
+BitrateProber::BitrateProber(const FieldTrialsView& field_trials)
+    : probing_state_(ProbingState::kDisabled),
+      next_probe_time_(Timestamp::PlusInfinity()),
+      total_probe_count_(0),
+      total_failed_probe_count_(0),
+      config_(&field_trials) {
+  SetEnabled(true);
+}
+
+void BitrateProber::SetEnabled(bool enable) {
+  if (enable) {
+    if (probing_state_ == ProbingState::kDisabled) {
+      probing_state_ = ProbingState::kInactive;
+      RTC_LOG(LS_INFO) << "Bandwidth probing enabled, set to inactive";
+    }
+  } else {
+    probing_state_ = ProbingState::kDisabled;
+    RTC_LOG(LS_INFO) << "Bandwidth probing disabled";
+  }
+}
+
+void BitrateProber::OnIncomingPacket(DataSize packet_size) {
+  // Don't initialize probing unless we have something large enough to start
+  // probing.
+  if (probing_state_ == ProbingState::kInactive && !clusters_.empty() &&
+      packet_size >= std::min(RecommendedMinProbeSize(), kMinProbePacketSize)) {
+    // Send next probe right away.
+    next_probe_time_ = Timestamp::MinusInfinity();
+    probing_state_ = ProbingState::kActive;
+  }
+}
+
+void BitrateProber::CreateProbeCluster(
+    const ProbeClusterConfig& cluster_config) {
+  RTC_DCHECK(probing_state_ != ProbingState::kDisabled);
+
+  total_probe_count_++;
+  while (!clusters_.empty() &&
+         cluster_config.at_time - clusters_.front().requested_at >
+             kProbeClusterTimeout) {
+    clusters_.pop();
+    total_failed_probe_count_++;
+  }
+
+  ProbeCluster cluster;
+  cluster.requested_at = cluster_config.at_time;
+  cluster.pace_info.probe_cluster_min_probes =
+      cluster_config.target_probe_count;
+  cluster.pace_info.probe_cluster_min_bytes =
+      (cluster_config.target_data_rate * cluster_config.target_duration)
+          .bytes();
+  RTC_DCHECK_GE(cluster.pace_info.probe_cluster_min_bytes, 0);
+  cluster.pace_info.send_bitrate_bps = cluster_config.target_data_rate.bps();
+  cluster.pace_info.probe_cluster_id = cluster_config.id;
+  clusters_.push(cluster);
+
+  RTC_LOG(LS_INFO) << "Probe cluster (bitrate:min bytes:min packets): ("
+                   << cluster.pace_info.send_bitrate_bps << ":"
+                   << cluster.pace_info.probe_cluster_min_bytes << ":"
+                   << cluster.pace_info.probe_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;
+}
+
+Timestamp BitrateProber::NextProbeTime(Timestamp now) const {
+  // Probing is not active or probing is already complete.
+  if (probing_state_ != ProbingState::kActive || clusters_.empty()) {
+    return Timestamp::PlusInfinity();
+  }
+
+  return next_probe_time_;
+}
+
+absl::optional<PacedPacketInfo> BitrateProber::CurrentCluster(Timestamp now) {
+  if (clusters_.empty() || probing_state_ != ProbingState::kActive) {
+    return absl::nullopt;
+  }
+
+  if (next_probe_time_.IsFinite() &&
+      now - next_probe_time_ > config_.max_probe_delay.Get()) {
+    RTC_DLOG(LS_WARNING) << "Probe delay too high"
+                            " (next_ms:"
+                         << next_probe_time_.ms() << ", now_ms: " << now.ms()
+                         << "), discarding probe cluster.";
+    clusters_.pop();
+    if (clusters_.empty()) {
+      probing_state_ = ProbingState::kSuspended;
+      return absl::nullopt;
+    }
+  }
+
+  PacedPacketInfo info = clusters_.front().pace_info;
+  info.probe_cluster_bytes_sent = clusters_.front().sent_bytes;
+  return info;
+}
+
+// Probe size is recommended based on the probe bitrate required. We choose
+// a minimum of twice `kMinProbeDeltaMs` interval to allow scheduling to be
+// feasible.
+DataSize BitrateProber::RecommendedMinProbeSize() const {
+  if (clusters_.empty()) {
+    return DataSize::Zero();
+  }
+  DataRate send_rate =
+      DataRate::BitsPerSec(clusters_.front().pace_info.send_bitrate_bps);
+  return 2 * send_rate * config_.min_probe_delta;
+}
+
+void BitrateProber::ProbeSent(Timestamp now, DataSize size) {
+  RTC_DCHECK(probing_state_ == ProbingState::kActive);
+  RTC_DCHECK(!size.IsZero());
+
+  if (!clusters_.empty()) {
+    ProbeCluster* cluster = &clusters_.front();
+    if (cluster->sent_probes == 0) {
+      RTC_DCHECK(cluster->started_at.IsInfinite());
+      cluster->started_at = now;
+    }
+    cluster->sent_bytes += size.bytes<int>();
+    cluster->sent_probes += 1;
+    next_probe_time_ = CalculateNextProbeTime(*cluster);
+    if (cluster->sent_bytes >= cluster->pace_info.probe_cluster_min_bytes &&
+        cluster->sent_probes >= cluster->pace_info.probe_cluster_min_probes) {
+      RTC_HISTOGRAM_COUNTS_100000("WebRTC.BWE.Probing.ProbeClusterSizeInBytes",
+                                  cluster->sent_bytes);
+      RTC_HISTOGRAM_COUNTS_100("WebRTC.BWE.Probing.ProbesPerCluster",
+                               cluster->sent_probes);
+      RTC_HISTOGRAM_COUNTS_10000("WebRTC.BWE.Probing.TimePerProbeCluster",
+                                 (now - cluster->started_at).ms());
+
+      clusters_.pop();
+    }
+    if (clusters_.empty()) {
+      probing_state_ = ProbingState::kSuspended;
+    }
+  }
+}
+
+Timestamp BitrateProber::CalculateNextProbeTime(
+    const ProbeCluster& cluster) const {
+  RTC_CHECK_GT(cluster.pace_info.send_bitrate_bps, 0);
+  RTC_CHECK(cluster.started_at.IsFinite());
+
+  // Compute the time delta from the cluster start to ensure probe bitrate stays
+  // close to the target bitrate. Result is in milliseconds.
+  DataSize sent_bytes = DataSize::Bytes(cluster.sent_bytes);
+  DataRate send_bitrate =
+      DataRate::BitsPerSec(cluster.pace_info.send_bitrate_bps);
+  TimeDelta delta = sent_bytes / send_bitrate;
+  return cluster.started_at + delta;
+}
+
+}  // namespace webrtc