Refactor NACK bitrate allocation

webrtc/modules/congestion_controller/congestion_controller.cc

Index: webrtc/modules/congestion_controller/congestion_controller.cc
diff --git a/webrtc/modules/congestion_controller/congestion_controller.cc b/webrtc/modules/congestion_controller/congestion_controller.cc
index 7582258185e4ab4b70c87720a9bc3ef702716afa..d1ab03af0f8fe92d54749fc5046dcc2c47362f38 100644
--- a/webrtc/modules/congestion_controller/congestion_controller.cc
+++ b/webrtc/modules/congestion_controller/congestion_controller.cc
@@ -17,6 +17,7 @@
 #include "webrtc/base/checks.h"
 #include "webrtc/base/constructormagic.h"
 #include "webrtc/base/logging.h"
+#include "webrtc/base/rate_limiter.h"
 #include "webrtc/base/socket.h"
 #include "webrtc/base/thread_annotations.h"
 #include "webrtc/modules/bitrate_controller/include/bitrate_controller.h"
@@ -32,6 +33,8 @@ namespace webrtc {
 namespace {
 
 static const uint32_t kTimeOffsetSwitchThreshold = 30;
+static const int64_t kMinRetransmitWindowSizeMs = 30;
+static const int64_t kMaxRetransmitWindowSizeMs = 1000;
 
 // Makes sure that the bitrate and the min, max values are in valid range.
 static void ClampBitrates(int* bitrate_bps,
@@ -164,6 +167,8 @@ CongestionController::CongestionController(
           new WrappingBitrateEstimator(remote_bitrate_observer, clock_)),
       bitrate_controller_(
           BitrateController::CreateBitrateController(clock_, event_log)),
+      retransmission_rate_limiter_(
+          new RateLimiter(clock, kMaxRetransmitWindowSizeMs)),
       remote_estimator_proxy_(clock_, packet_router_.get()),
       transport_feedback_adapter_(bitrate_controller_.get(), clock_),
       min_bitrate_bps_(RemoteBitrateEstimator::kDefaultMinBitrateBps),
@@ -191,6 +196,8 @@ CongestionController::CongestionController(
       // construction.
       bitrate_controller_(
           BitrateController::CreateBitrateController(clock_, event_log)),
+      retransmission_rate_limiter_(
+          new RateLimiter(clock, kMaxRetransmitWindowSizeMs)),
       remote_estimator_proxy_(clock_, packet_router_.get()),
       transport_feedback_adapter_(bitrate_controller_.get(), clock_),
       min_bitrate_bps_(RemoteBitrateEstimator::kDefaultMinBitrateBps),
@@ -266,6 +273,10 @@ CongestionController::GetTransportFeedbackObserver() {
   return &transport_feedback_adapter_;
 }
 
+RateLimiter* CongestionController::GetRetransmissionRateLimiter() {
+  return retransmission_rate_limiter_.get();
+}
+
 void CongestionController::SetAllocatedSendBitrateLimits(
     int min_send_bitrate_bps,
     int max_padding_bitrate_bps) {
@@ -299,6 +310,14 @@ void CongestionController::OnSentPacket(const rtc::SentPacket& sent_packet) {
 void CongestionController::OnRttUpdate(int64_t avg_rtt_ms, int64_t max_rtt_ms) {
   remote_bitrate_estimator_->OnRttUpdate(avg_rtt_ms, max_rtt_ms);
   transport_feedback_adapter_.OnRttUpdate(avg_rtt_ms, max_rtt_ms);
+
+  int64_t nack_window_size_ms = max_rtt_ms;
+  if (nack_window_size_ms > kMaxRetransmitWindowSizeMs) {
+    nack_window_size_ms = kMaxRetransmitWindowSizeMs;
+  } else if (nack_window_size_ms < kMinRetransmitWindowSizeMs) {
+    nack_window_size_ms = kMinRetransmitWindowSizeMs;
+  }
+  retransmission_rate_limiter_->SetWindowSize(nack_window_size_ms);
 }
 
 int64_t CongestionController::TimeUntilNextProcess() {
@@ -323,8 +342,10 @@ void CongestionController::MaybeTriggerOnNetworkChanged() {
   int64_t rtt;
   bool estimate_changed = bitrate_controller_->GetNetworkParameters(
       &bitrate_bps, &fraction_loss, &rtt);
-  if (estimate_changed)
+  if (estimate_changed) {
     pacer_->SetEstimatedBitrate(bitrate_bps);
+    retransmission_rate_limiter_->SetMaxRate(bitrate_bps);
+  }
 
   bitrate_bps = IsNetworkDown() || IsSendQueueFull() ? 0 : bitrate_bps;