From 3361af35ddfef81dcc35983a155c6521f63a138f Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?=C3=85sa=20Persson?= <asapersson@webrtc.org>
Date: Mon, 18 May 2020 11:01:33 +0200
Subject: [PATCH] Add option to disable reduced jitter delay through field
 trial.
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Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

Bug: none
Change-Id: Id07cb7dd69cd6198eb95a5e9c0987943471f7da2
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/175565
Reviewed-by: Christoffer Rodbro <crodbro@webrtc.org>
Commit-Queue: Åsa Persson <asapersson@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#31320}
---
 modules/video_coding/jitter_estimator.cc      | 34 +++++++++++--------
 modules/video_coding/jitter_estimator.h       |  1 +
 .../video_coding/jitter_estimator_tests.cc    | 16 +++++++++
 3 files changed, 37 insertions(+), 14 deletions(-)

diff --git a/modules/video_coding/jitter_estimator.cc b/modules/video_coding/jitter_estimator.cc
index cd505835d1..44e2a9811e 100644
--- a/modules/video_coding/jitter_estimator.cc
+++ b/modules/video_coding/jitter_estimator.cc
@@ -23,6 +23,7 @@
 #include "rtc_base/experiments/jitter_upper_bound_experiment.h"
 #include "rtc_base/numerics/safe_conversions.h"
 #include "system_wrappers/include/clock.h"
+#include "system_wrappers/include/field_trial.h"
 
 namespace webrtc {
 namespace {
@@ -50,6 +51,8 @@ VCMJitterEstimator::VCMJitterEstimator(Clock* clock)
       time_deviation_upper_bound_(
           JitterUpperBoundExperiment::GetUpperBoundSigmas().value_or(
               kDefaultMaxTimestampDeviationInSigmas)),
+      enable_reduced_delay_(
+          !field_trial::IsEnabled("WebRTC-ReducedJitterDelayKillSwitch")),
       clock_(clock) {
   Reset();
 }
@@ -395,22 +398,25 @@ int VCMJitterEstimator::GetJitterEstimate(
     }
   }
 
-  static const double kJitterScaleLowThreshold = 5.0;
-  static const double kJitterScaleHighThreshold = 10.0;
-  double fps = GetFrameRate();
-  // Ignore jitter for very low fps streams.
-  if (fps < kJitterScaleLowThreshold) {
-    if (fps == 0.0) {
-      return rtc::checked_cast<int>(std::max(0.0, jitterMS) + 0.5);
+  if (enable_reduced_delay_) {
+    static const double kJitterScaleLowThreshold = 5.0;
+    static const double kJitterScaleHighThreshold = 10.0;
+    double fps = GetFrameRate();
+    // Ignore jitter for very low fps streams.
+    if (fps < kJitterScaleLowThreshold) {
+      if (fps == 0.0) {
+        return rtc::checked_cast<int>(std::max(0.0, jitterMS) + 0.5);
+      }
+      return 0;
     }
-    return 0;
-  }
 
-  // Semi-low frame rate; scale by factor linearly interpolated from 0.0 at
-  // kJitterScaleLowThreshold to 1.0 at kJitterScaleHighThreshold.
-  if (fps < kJitterScaleHighThreshold) {
-    jitterMS = (1.0 / (kJitterScaleHighThreshold - kJitterScaleLowThreshold)) *
-               (fps - kJitterScaleLowThreshold) * jitterMS;
+    // Semi-low frame rate; scale by factor linearly interpolated from 0.0 at
+    // kJitterScaleLowThreshold to 1.0 at kJitterScaleHighThreshold.
+    if (fps < kJitterScaleHighThreshold) {
+      jitterMS =
+          (1.0 / (kJitterScaleHighThreshold - kJitterScaleLowThreshold)) *
+          (fps - kJitterScaleLowThreshold) * jitterMS;
+    }
   }
 
   return rtc::checked_cast<int>(std::max(0.0, jitterMS) + 0.5);
diff --git a/modules/video_coding/jitter_estimator.h b/modules/video_coding/jitter_estimator.h
index d9798b40a1..1d69b95769 100644
--- a/modules/video_coding/jitter_estimator.h
+++ b/modules/video_coding/jitter_estimator.h
@@ -150,6 +150,7 @@ class VCMJitterEstimator {
 
   rtc::RollingAccumulator<uint64_t> fps_counter_;
   const double time_deviation_upper_bound_;
+  const bool enable_reduced_delay_;
   Clock* clock_;
 };
 
diff --git a/modules/video_coding/jitter_estimator_tests.cc b/modules/video_coding/jitter_estimator_tests.cc
index 1ad9abb56f..14baae7e81 100644
--- a/modules/video_coding/jitter_estimator_tests.cc
+++ b/modules/video_coding/jitter_estimator_tests.cc
@@ -72,6 +72,22 @@ TEST_F(TestVCMJitterEstimator, TestLowRate) {
   }
 }
 
+TEST_F(TestVCMJitterEstimator, TestLowRateDisabled) {
+  test::ScopedFieldTrials field_trials(
+      "WebRTC-ReducedJitterDelayKillSwitch/Enabled/");
+  SetUp();
+
+  ValueGenerator gen(10);
+  uint64_t time_delta_us = rtc::kNumMicrosecsPerSec / 5;
+  for (int i = 0; i < 60; ++i) {
+    estimator_->UpdateEstimate(gen.Delay(), gen.FrameSize());
+    AdvanceClock(time_delta_us);
+    if (i > 2)
+      EXPECT_GT(estimator_->GetJitterEstimate(0, absl::nullopt), 0);
+    gen.Advance();
+  }
+}
+
 TEST_F(TestVCMJitterEstimator, TestUpperBound) {
   struct TestContext {
     TestContext()