Add AlrDetector

webrtc/modules/congestion_controller/alr_detector.cc

+/*
+ *  Copyright (c) 2016 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/congestion_controller/alr_detector.h"
+
+#include "webrtc/base/checks.h"
+#include "webrtc/base/logging.h"
+
+namespace {
+
+// Time period over which outgoing traffic is measured and considered a single
+// data point.
+constexpr int kMeasurementPeriodMs = 100;
+
+// Minimum number of consecutive measurements over |kMeasurementPeriodMs| time
+// that indicate sending rate is below |kUsagePercent| to consider being
+// application limited.
+constexpr int kApplicationLimitedThreshold = 5;
+
+// Sent traffic percentage as a function of network capaicty to consider traffic
+// as application limited.
+// NOTE: This is intentionally conservative at the moment until BW adjustments
+// of application limited region is fine tuned.
+constexpr int kUsagePercent = 30;
+
+}  // namespace
+
+namespace webrtc {
+
+AlrDetector::AlrDetector()
+    : measurement_interval_bytes_sent_(0),
+      measurement_interval_elapsed_time_ms_(0),
+      estimated_bitrate_bps_(0),
+      application_limited_count_(0) {}
+
+AlrDetector::~AlrDetector() {}
+
+void AlrDetector::OnBytesSent(size_t bytes_sent, int64_t elapsed_time_ms) {
+  if (measurement_interval_elapsed_time_ms_ > kMeasurementPeriodMs) {
+    RTC_DCHECK(estimated_bitrate_bps_);
+    int max_bytes =
+        (measurement_interval_elapsed_time_ms_ * estimated_bitrate_bps_) /
+        (8 * 1000);
+    RTC_DCHECK_GT(max_bytes, 0);
+    int utilization = (measurement_interval_bytes_sent_ * 100) / max_bytes;
+    if (utilization < kUsagePercent) {
+      application_limited_count_++;
+      if (application_limited_count_ == kApplicationLimitedThreshold)
+        LOG(LS_INFO) << "ALR start";
+    } else {
+      if (application_limited_count_ >= kApplicationLimitedThreshold)
+        LOG(LS_INFO) << "ALR stop";
+      application_limited_count_ = 0;
+    }
+    measurement_interval_elapsed_time_ms_ = elapsed_time_ms;
+    measurement_interval_bytes_sent_ = bytes_sent;
+  } else {
+    measurement_interval_elapsed_time_ms_ += elapsed_time_ms;
+    measurement_interval_bytes_sent_ += bytes_sent;
+  }
+}
+
+void AlrDetector::SetEstimatedBitrate(int bitrate_bps) {
+  RTC_DCHECK(bitrate_bps);
+  estimated_bitrate_bps_ = bitrate_bps;
+}
+
+bool AlrDetector::InApplicationLimitedRegion() {
+  return application_limited_count_ >= kApplicationLimitedThreshold;
+}
+
+}  // namespace webrtc