From ea3dddf1d0880e89d84a7e502f65c65993d4169d Mon Sep 17 00:00:00 2001
From: Sebastian Jansson <srte@webrtc.org>
Date: Tue, 16 Jul 2019 16:31:50 +0200
Subject: [PATCH] Use capacity bounds in AimdRateControl if available.
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

Bug: webrtc:10742
Change-Id: I139f7053d33092efe6430d82596b05c730855383
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/145725
Commit-Queue: Sebastian Jansson <srte@webrtc.org>
Reviewed-by: Björn Terelius <terelius@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#28584}
---
 api/transport/network_types.h                 |  7 ++--
 .../aimd_rate_control.cc                      | 40 ++++++++++++-------
 2 files changed, 28 insertions(+), 19 deletions(-)

diff --git a/api/transport/network_types.h b/api/transport/network_types.h
index 45b651ea73..9e79bce844 100644
--- a/api/transport/network_types.h
+++ b/api/transport/network_types.h
@@ -236,11 +236,10 @@ struct NetworkStateEstimate {
 
   // Total estimated link capacity.
   DataRate link_capacity = DataRate::MinusInfinity();
-  // Lower bound of link capacity estimate.
+  // Used as a safe measure of available capacity.
   DataRate link_capacity_lower = DataRate::MinusInfinity();
-  // Expected available capacity for sending data after cross traffic is taken
-  // into consideration.
-  DataRate available_capacity = DataRate::MinusInfinity();
+  // Used as limit for increasing bitrate.
+  DataRate link_capacity_upper = DataRate::MinusInfinity();
 
   TimeDelta pre_link_buffer_delay = TimeDelta::MinusInfinity();
   TimeDelta post_link_buffer_delay = TimeDelta::MinusInfinity();
diff --git a/modules/remote_bitrate_estimator/aimd_rate_control.cc b/modules/remote_bitrate_estimator/aimd_rate_control.cc
index 1e5d292cf5..0b523819f3 100644
--- a/modules/remote_bitrate_estimator/aimd_rate_control.cc
+++ b/modules/remote_bitrate_estimator/aimd_rate_control.cc
@@ -305,18 +305,24 @@ DataRate AimdRateControl::ChangeBitrate(DataRate new_bitrate,
 
     case kRcDecrease:
       if (network_estimate_ && capacity_deviation_ratio_threshold_) {
-        // If we have a low variance network estimate, we use it over the
-        // acknowledged rate to avoid dropping the bitrate too far. This avoids
-        // overcompensating when the send rate is lower than the capacity.
-        double deviation_ratio = network_estimate_->link_capacity_std_dev /
-                                 network_estimate_->link_capacity;
-        if (deviation_ratio < *capacity_deviation_ratio_threshold_) {
-          double available_ratio =
-              std::max(0.0, 1.0 - network_estimate_->cross_traffic_ratio *
-                                      cross_traffic_factor_);
-          DataRate available_rate =
-              network_estimate_->link_capacity * available_ratio;
-          estimated_throughput = std::max(available_rate, estimated_throughput);
+        DataRate lower_bound = network_estimate_->link_capacity_lower;
+        // TODO(srte): Remove this when link_capacity_lower is available.
+        if (lower_bound.IsInfinite()) {
+          // If we have a low variance network estimate, we use it over the
+          // acknowledged rate to avoid dropping the bitrate too far. This
+          // avoids overcompensating when the send rate is lower than the
+          // capacity.
+          double deviation_ratio = network_estimate_->link_capacity_std_dev /
+                                   network_estimate_->link_capacity;
+          if (deviation_ratio < *capacity_deviation_ratio_threshold_) {
+            double available_ratio =
+                std::max(0.0, 1.0 - network_estimate_->cross_traffic_ratio *
+                                        cross_traffic_factor_);
+            lower_bound = network_estimate_->link_capacity * available_ratio;
+          }
+        }
+        if (lower_bound > DataRate::Zero()) {
+          estimated_throughput = std::max(lower_bound, estimated_throughput);
         }
       }
       if (estimated_throughput > low_throughput_threshold_) {
@@ -388,9 +394,13 @@ DataRate AimdRateControl::ClampBitrate(DataRate new_bitrate,
   }
 
   if (network_estimate_ && capacity_limit_deviation_factor_) {
-    DataRate upper_bound = network_estimate_->link_capacity +
-                           network_estimate_->link_capacity_std_dev *
-                               capacity_limit_deviation_factor_.Value();
+    DataRate upper_bound = network_estimate_->link_capacity_upper;
+    // TODO(srte): Remove this when link_capacity_lower is available.
+    if (upper_bound.IsMinusInfinity()) {
+      upper_bound = network_estimate_->link_capacity +
+                    network_estimate_->link_capacity_std_dev *
+                        capacity_limit_deviation_factor_.Value();
+    }
     new_bitrate = std::min(new_bitrate, upper_bound);
   }
   new_bitrate = std::max(new_bitrate, min_configured_bitrate_);