Add probing to recover faster from large bitrate drops.

webrtc/modules/congestion_controller/probe_controller_unittest.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 <memory>
@@ skipping 15 matching lines @@
 
 namespace {
 
 constexpr int kMinBitrateBps = 100;
 constexpr int kStartBitrateBps = 300;
 constexpr int kMaxBitrateBps = 10000;
 
 constexpr int kExponentialProbingTimeoutMs = 5000;
 
 constexpr int kAlrProbeInterval = 5000;
+constexpr int kAlrEndedTimeoutMs = 3000;
+constexpr int kBitrateDropTimeoutMs = 5000;
 
 }  // namespace
 
 class ProbeControllerTest : public ::testing::Test {
  protected:
   ProbeControllerTest() : clock_(100000000L) {
     probe_controller_.reset(new ProbeController(&pacer_, &clock_));
   }
   ~ProbeControllerTest() override {}
 
@@ skipping 67 matching lines @@
                                  kMaxBitrateBps);
 
   // Advance far enough to cause a time out in waiting for probing result.
   clock_.AdvanceTimeMilliseconds(kExponentialProbingTimeoutMs);
   probe_controller_->Process();
 
   EXPECT_CALL(pacer_, CreateProbeCluster(_)).Times(0);
   probe_controller_->SetEstimatedBitrate(1800);
 }
 
-TEST_F(ProbeControllerTest, ProbeAfterEstimateDropInAlr) {
+TEST_F(ProbeControllerTest, RequestProbeInAlr) {
   EXPECT_CALL(pacer_, CreateProbeCluster(_)).Times(2);
   probe_controller_->SetBitrates(kMinBitrateBps, kStartBitrateBps,
                                  kMaxBitrateBps);
   probe_controller_->SetEstimatedBitrate(500);
   testing::Mock::VerifyAndClearExpectations(&pacer_);
-
-  // When bandwidth estimate drops the controller should send a probe at the
-  // previous bitrate.
-  EXPECT_CALL(pacer_, CreateProbeCluster(500)).Times(1);
+  EXPECT_CALL(pacer_, CreateProbeCluster(0.85 * 500)).Times(1);
   EXPECT_CALL(pacer_, GetApplicationLimitedRegionStartTime())
       .WillRepeatedly(
           Return(rtc::Optional<int64_t>(clock_.TimeInMilliseconds())));
   clock_.AdvanceTimeMilliseconds(kAlrProbeInterval + 1);
   probe_controller_->Process();
-  probe_controller_->SetEstimatedBitrate(50);
+  probe_controller_->SetEstimatedBitrate(250);
+  probe_controller_->RequestProbe();
+}
+
+TEST_F(ProbeControllerTest, RequestProbeWhenAlrEndedRecently) {
+  EXPECT_CALL(pacer_, CreateProbeCluster(_)).Times(2);
+  probe_controller_->SetBitrates(kMinBitrateBps, kStartBitrateBps,
+                                 kMaxBitrateBps);
+  probe_controller_->SetEstimatedBitrate(500);
+  testing::Mock::VerifyAndClearExpectations(&pacer_);
+  EXPECT_CALL(pacer_, CreateProbeCluster(0.85 * 500)).Times(1);
+  EXPECT_CALL(pacer_, GetApplicationLimitedRegionStartTime())
+      .WillRepeatedly(Return(rtc::Optional<int64_t>()));
+  clock_.AdvanceTimeMilliseconds(kAlrProbeInterval + 1);
+  probe_controller_->Process();
+  probe_controller_->SetEstimatedBitrate(250);
+  probe_controller_->SetAlrEndedTimeMs(clock_.TimeInMilliseconds());
+  clock_.AdvanceTimeMilliseconds(kAlrEndedTimeoutMs - 1);
+  probe_controller_->RequestProbe();
+}
+
+TEST_F(ProbeControllerTest, RequestProbeWhenAlrNotEndedRecently) {
+  EXPECT_CALL(pacer_, CreateProbeCluster(_)).Times(2);
+  probe_controller_->SetBitrates(kMinBitrateBps, kStartBitrateBps,
+                                 kMaxBitrateBps);
+  probe_controller_->SetEstimatedBitrate(500);
+  testing::Mock::VerifyAndClearExpectations(&pacer_);
+  EXPECT_CALL(pacer_, CreateProbeCluster(_)).Times(0);
+  EXPECT_CALL(pacer_, GetApplicationLimitedRegionStartTime())
+      .WillRepeatedly(Return(rtc::Optional<int64_t>()));
+  clock_.AdvanceTimeMilliseconds(kAlrProbeInterval + 1);
+  probe_controller_->Process();
+  probe_controller_->SetEstimatedBitrate(250);
+  probe_controller_->SetAlrEndedTimeMs(clock_.TimeInMilliseconds());
+  clock_.AdvanceTimeMilliseconds(kAlrEndedTimeoutMs + 1);
+  probe_controller_->RequestProbe();
+}
+
+TEST_F(ProbeControllerTest, RequestProbeWhenBweDropNotRecent) {
+  EXPECT_CALL(pacer_, CreateProbeCluster(_)).Times(2);
+  probe_controller_->SetBitrates(kMinBitrateBps, kStartBitrateBps,
+                                 kMaxBitrateBps);
+  probe_controller_->SetEstimatedBitrate(500);
+  testing::Mock::VerifyAndClearExpectations(&pacer_);
+  EXPECT_CALL(pacer_, CreateProbeCluster(_)).Times(0);
+  EXPECT_CALL(pacer_, GetApplicationLimitedRegionStartTime())
+      .WillRepeatedly(
+          Return(rtc::Optional<int64_t>(clock_.TimeInMilliseconds())));
+  clock_.AdvanceTimeMilliseconds(kAlrProbeInterval + 1);
+  probe_controller_->Process();
+  probe_controller_->SetEstimatedBitrate(250);
+  clock_.AdvanceTimeMilliseconds(kBitrateDropTimeoutMs + 1);
+  probe_controller_->RequestProbe();
 }
 
 TEST_F(ProbeControllerTest, PeriodicProbing) {
   EXPECT_CALL(pacer_, CreateProbeCluster(_)).Times(2);
   probe_controller_->EnablePeriodicAlrProbing(true);
   probe_controller_->SetBitrates(kMinBitrateBps, kStartBitrateBps,
                                  kMaxBitrateBps);
   probe_controller_->SetEstimatedBitrate(500);
   testing::Mock::VerifyAndClearExpectations(&pacer_);
 
@@ skipping 64 matching lines @@
   probe_controller_->SetEstimatedBitrate(60 * kMbpsMultiplier);
   testing::Mock::VerifyAndClearExpectations(&pacer_);
 
   // Verify that repeated probes aren't sent.
   EXPECT_CALL(pacer_, CreateProbeCluster(_)).Times(0);
   probe_controller_->SetEstimatedBitrate(100 * kMbpsMultiplier);
 }
 
 }  // namespace test
 }  // namespace webrtc