Add cap to video jitter buffer size/latency in experiment branches only.

Bug: webrtc:10664
Change-Id: I03762c8b318f26f2689e89545aa8cc8e5b4a4329
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/138081
Commit-Queue: Michael Horowitz <mhoro@webrtc.org>
Reviewed-by: Stefan Holmer <stefan@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#28155}

modules/video_coding/frame_buffer2.cc

@@ -299,10 +299,14 @@ EncodedFrame* FrameBuffer::GetNextFrame() {
     }
 
     float rtt_mult = protection_mode_ == kProtectionNackFEC ? 0.0 : 1.0;
+    absl::optional<double> rtt_mult_add_cap_ms = absl::nullopt;
     if (RttMultExperiment::RttMultEnabled()) {
       rtt_mult = RttMultExperiment::GetRttMultValue();
+      // TODO(mhoro): add RttMultExperiment::GetJitterEstCapValue();
+      rtt_mult_add_cap_ms = 200.0;
     }
-    timing_->SetJitterDelay(jitter_estimator_.GetJitterEstimate(rtt_mult));
+    timing_->SetJitterDelay(
+        jitter_estimator_.GetJitterEstimate(rtt_mult, rtt_mult_add_cap_ms));
     timing_->UpdateCurrentDelay(render_time_ms, now_ms);
   } else {
     if (RttMultExperiment::RttMultEnabled() || add_rtt_to_playout_delay_)

modules/video_coding/jitter_buffer.cc

@@ -582,7 +582,7 @@ void VCMJitterBuffer::FindAndInsertContinuousFramesWithState(
 uint32_t VCMJitterBuffer::EstimatedJitterMs() {
   rtc::CritScope cs(&crit_sect_);
   const double rtt_mult = 1.0f;
-  return jitter_estimate_.GetJitterEstimate(rtt_mult);
+  return jitter_estimate_.GetJitterEstimate(rtt_mult, absl::nullopt);
 }
 
 void VCMJitterBuffer::SetNackSettings(size_t max_nack_list_size,

modules/video_coding/jitter_estimator.cc

@@ -374,7 +374,9 @@ void VCMJitterEstimator::UpdateRtt(int64_t rttMs) {
 
 // Returns the current filtered estimate if available,
 // otherwise tries to calculate an estimate.
-int VCMJitterEstimator::GetJitterEstimate(double rttMultiplier) {
+int VCMJitterEstimator::GetJitterEstimate(
+    double rttMultiplier,
+    absl::optional<double> rttMultAddCapMs) {
   double jitterMS = CalculateEstimate() + OPERATING_SYSTEM_JITTER;
   uint64_t now = clock_->TimeInMicroseconds();
 
@@ -383,8 +385,14 @@ int VCMJitterEstimator::GetJitterEstimate(double rttMultiplier) {
 
   if (_filterJitterEstimate > jitterMS)
     jitterMS = _filterJitterEstimate;
-  if (_nackCount >= _nackLimit)
-    jitterMS += _rttFilter.RttMs() * rttMultiplier;
+  if (_nackCount >= _nackLimit) {
+    if (rttMultAddCapMs.has_value()) {
+      jitterMS +=
+          std::min(_rttFilter.RttMs() * rttMultiplier, rttMultAddCapMs.value());
+    } else {
+      jitterMS += _rttFilter.RttMs() * rttMultiplier;
+    }
+  }
 
   static const double kJitterScaleLowThreshold = 5.0;
   static const double kJitterScaleHighThreshold = 10.0;

modules/video_coding/jitter_estimator.h

@@ -46,7 +46,8 @@ class VCMJitterEstimator {
   //          - rttMultiplier  : RTT param multiplier (when applicable).
   //
   // Return value              : Jitter estimate in milliseconds.
-  virtual int GetJitterEstimate(double rttMultiplier);
+  virtual int GetJitterEstimate(double rttMultiplier,
+                                absl::optional<double> rttMultAddCapMs);
 
   // Updates the nack counter.
   void FrameNacked();

modules/video_coding/jitter_estimator_tests.cc

@@ -67,22 +67,43 @@ TEST_F(TestVCMJitterEstimator, TestLowRate) {
     estimator_->UpdateEstimate(gen.Delay(), gen.FrameSize());
     AdvanceClock(time_delta_us);
     if (i > 2)
-      EXPECT_EQ(estimator_->GetJitterEstimate(0), 0);
+      EXPECT_EQ(estimator_->GetJitterEstimate(0, absl::nullopt), 0);
     gen.Advance();
   }
 }
 
 TEST_F(TestVCMJitterEstimator, TestUpperBound) {
   struct TestContext {
-    TestContext() : upper_bound(0.0), percentiles(1000) {}
+    TestContext()
+        : upper_bound(0.0),
+          rtt_mult(0),
+          rtt_mult_add_cap_ms(absl::nullopt),
+          percentiles(1000) {}
     double upper_bound;
+    double rtt_mult;
+    absl::optional<double> rtt_mult_add_cap_ms;
     rtc::HistogramPercentileCounter percentiles;
   };
-  std::vector<TestContext> test_cases(2);
+  std::vector<TestContext> test_cases(4);
 
-  test_cases[0].upper_bound = 100.0;  // First use essentially no cap.
-  test_cases[1].upper_bound = 3.5;    // Second, reasonably small cap.
+  // Large upper bound, rtt_mult = 0, and nullopt for rtt_mult addition cap.
+  test_cases[0].upper_bound = 100.0;
+  test_cases[0].rtt_mult = 0;
+  test_cases[0].rtt_mult_add_cap_ms = absl::nullopt;
+  // Small upper bound, rtt_mult = 0, and nullopt for rtt_mult addition cap.
+  test_cases[1].upper_bound = 3.5;
+  test_cases[1].rtt_mult = 0;
+  test_cases[1].rtt_mult_add_cap_ms = absl::nullopt;
+  // Large upper bound, rtt_mult = 1, and large rtt_mult addition cap value.
+  test_cases[2].upper_bound = 1000.0;
+  test_cases[2].rtt_mult = 1.0;
+  test_cases[2].rtt_mult_add_cap_ms = 200.0;
+  // Large upper bound, rtt_mult = 1, and small rtt_mult addition cap value.
+  test_cases[3].upper_bound = 1000.0;
+  test_cases[3].rtt_mult = 1.0;
+  test_cases[3].rtt_mult_add_cap_ms = 10.0;
 
+  // Test jitter buffer upper_bound and rtt_mult addition cap sizes.
   for (TestContext& context : test_cases) {
     // Set up field trial and reset jitter estimator.
     char string_buf[64];
@@ -94,11 +115,15 @@ TEST_F(TestVCMJitterEstimator, TestUpperBound) {
 
     ValueGenerator gen(50);
     uint64_t time_delta_us = rtc::kNumMicrosecsPerSec / 30;
+    constexpr int64_t kRttMs = 250;
     for (int i = 0; i < 100; ++i) {
       estimator_->UpdateEstimate(gen.Delay(), gen.FrameSize());
       AdvanceClock(time_delta_us);
+      estimator_->FrameNacked();      // To test rtt_mult.
+      estimator_->UpdateRtt(kRttMs);  // To test rtt_mult.
       context.percentiles.Add(
-          static_cast<uint32_t>(estimator_->GetJitterEstimate(0)));
+          static_cast<uint32_t>(estimator_->GetJitterEstimate(
+              context.rtt_mult, context.rtt_mult_add_cap_ms)));
       gen.Advance();
     }
   }
@@ -112,6 +137,11 @@ TEST_F(TestVCMJitterEstimator, TestUpperBound) {
   uint32_t max_unbound = *test_cases[0].percentiles.GetPercentile(1.0);
   uint32_t max_bounded = *test_cases[1].percentiles.GetPercentile(1.0);
   EXPECT_GT(max_unbound, static_cast<uint32_t>(max_bounded * 1.25));
+
+  // With rtt_mult = 1, max should be lower with small rtt_mult add cap value.
+  max_unbound = *test_cases[2].percentiles.GetPercentile(1.0);
+  max_bounded = *test_cases[3].percentiles.GetPercentile(1.0);
+  EXPECT_GT(max_unbound, static_cast<uint32_t>(max_bounded * 1.25));
 }
 
 }  // namespace webrtc