[feat] add robust throughput estimator

src/qos/acknowledged_bitrate_estimator_interface.h

@@ -22,6 +22,44 @@
 
 namespace webrtc {
 
+struct RobustThroughputEstimatorSettings {
+  static constexpr char kKey[] = "WebRTC-Bwe-RobustThroughputEstimatorSettings";
+
+  RobustThroughputEstimatorSettings();
+
+  // Set `enabled` to true to use the RobustThroughputEstimator, false to use
+  // the AcknowledgedBitrateEstimator.
+  bool enabled = true;
+
+  // The estimator keeps the smallest window containing at least
+  // `window_packets` and at least the packets received during the last
+  // `min_window_duration` milliseconds.
+  // (This means that it may store more than `window_packets` at high bitrates,
+  // and a longer duration than `min_window_duration` at low bitrates.)
+  // However, if will never store more than kMaxPackets (for performance
+  // reasons), and never longer than max_window_duration (to avoid very old
+  // packets influencing the estimate for example when sending is paused).
+  unsigned window_packets = 20;
+  unsigned max_window_packets = 500;
+  TimeDelta min_window_duration = TimeDelta::Seconds(1);
+  TimeDelta max_window_duration = TimeDelta::Seconds(5);
+
+  // The estimator window requires at least `required_packets` packets
+  // to produce an estimate.
+  unsigned required_packets = 10;
+
+  // If audio packets aren't included in allocation (i.e. the
+  // estimated available bandwidth is divided only among the video
+  // streams), then `unacked_weight` should be set to 0.
+  // If audio packets are included in allocation, but not in bandwidth
+  // estimation (i.e. they don't have transport-wide sequence numbers,
+  // but we nevertheless divide the estimated available bandwidth among
+  // both audio and video streams), then `unacked_weight` should be set to 1.
+  // If all packets have transport-wide sequence numbers, then the value
+  // of `unacked_weight` doesn't matter.
+  double unacked_weight = 1.0;
+};
+
 class AcknowledgedBitrateEstimatorInterface {
  public:
   static std::unique_ptr<AcknowledgedBitrateEstimatorInterface> Create();