Reset the delay-based estimate before forcing a new loss-based send rate.

Without this fix the new estimate would be capped by the old delay-based
estimate. Also revert a part of https://codereview.webrtc.org/2949203002
that only pushes updates from the delay-based estimate if the estimate
change. This is reverted as a safety precaution to prevent situations
where the two estimators get out of sync.

Bug: webrtc:8495
Change-Id: I153f2af4a822e67d47c52bffc97a73ab931a15dd
Reviewed-on: https://webrtc-review.googlesource.com/20981
Reviewed-by: Stefan Holmer <stefan@webrtc.org>
Commit-Queue: Björn Terelius <terelius@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#20614}

modules/bitrate_controller/bitrate_controller_impl.cc

@@ -147,11 +147,13 @@ void BitrateControllerImpl::OnDelayBasedBweResult(
     return;
   {
     rtc::CritScope cs(&critsect_);
-    bandwidth_estimation_.UpdateDelayBasedEstimate(clock_->TimeInMilliseconds(),
-                                                   result.target_bitrate_bps);
     if (result.probe) {
       bandwidth_estimation_.SetSendBitrate(result.target_bitrate_bps);
     }
+    // Since SetSendBitrate now resets the delay-based estimate, we have to call
+    // UpdateDelayBasedEstimate after SetSendBitrate.
+    bandwidth_estimation_.UpdateDelayBasedEstimate(clock_->TimeInMilliseconds(),
+                                                   result.target_bitrate_bps);
   }
   MaybeTriggerOnNetworkChanged();
 }

modules/bitrate_controller/send_side_bandwidth_estimation.cc

@@ -158,6 +158,7 @@ void SendSideBandwidthEstimation::SetBitrates(int send_bitrate,
 
 void SendSideBandwidthEstimation::SetSendBitrate(int bitrate) {
   RTC_DCHECK_GT(bitrate, 0);
+  delay_based_bitrate_bps_ = 0;  // Reset to avoid being capped by the estimate.
   CapBitrateToThresholds(Clock::GetRealTimeClock()->TimeInMilliseconds(),
                          bitrate);
   // Clear last sent bitrate history so the new value can be used directly

modules/bitrate_controller/send_side_bandwidth_estimation_unittest.cc

@@ -136,4 +136,33 @@ TEST(SendSideBweTest, DoesntReapplyBitrateDecreaseWithoutFollowingRemb) {
   EXPECT_EQ(kRttMs, rtt_ms);
 }
 
+TEST(SendSideBweTest, SettingSendBitrateOverridesDelayBasedEstimate) {
+  ::testing::NiceMock<MockRtcEventLog> event_log;
+  SendSideBandwidthEstimation bwe(&event_log);
+  static const int kMinBitrateBps = 10000;
+  static const int kMaxBitrateBps = 10000000;
+  static const int kInitialBitrateBps = 300000;
+  static const int kDelayBasedBitrateBps = 350000;
+  static const int kForcedHighBitrate = 2500000;
+
+  int64_t now_ms = 0;
+  int bitrate_bps;
+  uint8_t fraction_loss;
+  int64_t rtt_ms;
+
+  bwe.SetMinMaxBitrate(kMinBitrateBps, kMaxBitrateBps);
+  bwe.SetSendBitrate(kInitialBitrateBps);
+
+  bwe.UpdateDelayBasedEstimate(now_ms, kDelayBasedBitrateBps);
+  bwe.UpdateEstimate(now_ms);
+  bwe.CurrentEstimate(&bitrate_bps, &fraction_loss, &rtt_ms);
+  EXPECT_GE(bitrate_bps, kInitialBitrateBps);
+  EXPECT_LE(bitrate_bps, kDelayBasedBitrateBps);
+
+  bwe.SetSendBitrate(kForcedHighBitrate);
+  bwe.CurrentEstimate(&bitrate_bps, &fraction_loss, &rtt_ms);
+  EXPECT_EQ(bitrate_bps, kForcedHighBitrate);
+}
+
+
 }  // namespace webrtc

modules/congestion_controller/delay_based_bwe.cc

@@ -296,10 +296,8 @@ bool DelayBasedBwe::UpdateEstimate(int64_t now_ms,
   const RateControlInput input(
       overusing ? BandwidthUsage::kBwOverusing : detector_.State(),
       acked_bitrate_bps, 0);
-  uint32_t prev_target_bitrate_bps = rate_control_.LatestEstimate();
   *target_bitrate_bps = rate_control_.Update(&input, now_ms);
-  return rate_control_.ValidEstimate() &&
+  return rate_control_.ValidEstimate();
-         prev_target_bitrate_bps != *target_bitrate_bps;
 }
 
 void DelayBasedBwe::OnRttUpdate(int64_t avg_rtt_ms, int64_t max_rtt_ms) {