From 2afff37ba007429cd1cb65369ee815bceee6f3c9 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?=C3=85sa=20Persson?= <asapersson@webrtc.org>
Date: Thu, 11 Feb 2021 17:31:11 +0100
Subject: [PATCH] Update field trial for allowing cropped resolution when
 limiting max layers.
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Make max_ratio:0.1 default.

BUG: webrtc:12459
Change-Id: Ia938836f2b95467fce66a38f2525b1d2be1a352b
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/206803
Commit-Queue: Åsa Persson <asapersson@webrtc.org>
Reviewed-by: Ilya Nikolaevskiy <ilnik@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#33261}
---
 media/engine/simulcast.cc          |  4 +++-
 media/engine/simulcast_unittest.cc | 34 +++++++++++++++++++++++++-----
 2 files changed, 32 insertions(+), 6 deletions(-)

diff --git a/media/engine/simulcast.cc b/media/engine/simulcast.cc
index 6b3ed71553..ebc6a240fe 100644
--- a/media/engine/simulcast.cc
+++ b/media/engine/simulcast.cc
@@ -42,6 +42,8 @@ constexpr webrtc::DataRate Interpolate(const webrtc::DataRate& a,
 constexpr char kUseLegacySimulcastLayerLimitFieldTrial[] =
     "WebRTC-LegacySimulcastLayerLimit";
 
+constexpr double kDefaultMaxRoundupRate = 0.1;
+
 // TODO(webrtc:12415): Flip this to a kill switch when this feature launches.
 bool EnableLowresBitrateInterpolation(
     const webrtc::WebRtcKeyValueConfig& trials) {
@@ -209,7 +211,7 @@ SimulcastFormat InterpolateSimulcastFormat(
                      static_cast<float>(total_pixels_up - total_pixels_down);
 
   // Use upper resolution if |rate| is below the configured threshold.
-  size_t max_layers = (max_roundup_rate && rate < max_roundup_rate.value())
+  size_t max_layers = (rate < max_roundup_rate.value_or(kDefaultMaxRoundupRate))
                           ? formats[index - 1].max_layers
                           : formats[index].max_layers;
   webrtc::DataRate max_bitrate = Interpolate(formats[index - 1].max_bitrate,
diff --git a/media/engine/simulcast_unittest.cc b/media/engine/simulcast_unittest.cc
index 98ee109d1a..47a9db75a1 100644
--- a/media/engine/simulcast_unittest.cc
+++ b/media/engine/simulcast_unittest.cc
@@ -377,7 +377,9 @@ TEST(SimulcastTest, BitratesForCloseToStandardResolution) {
   }
 }
 
-TEST(SimulcastTest, MaxLayers) {
+TEST(SimulcastTest, MaxLayersWithRoundUpDisabled) {
+  test::ScopedFieldTrials field_trials(
+      "WebRTC-SimulcastLayerLimitRoundUp/max_ratio:0.0/");
   FieldTrialBasedConfig trials;
   const size_t kMinLayers = 1;
   const int kMaxLayers = 3;
@@ -403,9 +405,8 @@ TEST(SimulcastTest, MaxLayers) {
   EXPECT_EQ(1u, streams.size());
 }
 
-TEST(SimulcastTest, MaxLayersWithFieldTrial) {
-  test::ScopedFieldTrials field_trials(
-      "WebRTC-SimulcastLayerLimitRoundUp/max_ratio:0.1/");
+TEST(SimulcastTest, MaxLayersWithDefaultRoundUpRatio) {
+  // Default: "WebRTC-SimulcastLayerLimitRoundUp/max_ratio:0.1/"
   FieldTrialBasedConfig trials;
   const size_t kMinLayers = 1;
   const int kMaxLayers = 3;
@@ -420,7 +421,7 @@ TEST(SimulcastTest, MaxLayersWithFieldTrial) {
                                         kBitratePriority, kQpMax, !kScreenshare,
                                         true, trials);
   EXPECT_EQ(3u, streams.size());
-  streams = cricket::GetSimulcastConfig(kMinLayers, kMaxLayers, 960, 510,
+  streams = cricket::GetSimulcastConfig(kMinLayers, kMaxLayers, 960, 508,
                                         kBitratePriority, kQpMax, !kScreenshare,
                                         true, trials);
   EXPECT_EQ(2u, streams.size());
@@ -439,6 +440,29 @@ TEST(SimulcastTest, MaxLayersWithFieldTrial) {
   EXPECT_EQ(1u, streams.size());
 }
 
+TEST(SimulcastTest, MaxLayersWithRoundUpRatio) {
+  test::ScopedFieldTrials field_trials(
+      "WebRTC-SimulcastLayerLimitRoundUp/max_ratio:0.13/");
+  FieldTrialBasedConfig trials;
+  const size_t kMinLayers = 1;
+  const int kMaxLayers = 3;
+
+  std::vector<VideoStream> streams;
+  streams = cricket::GetSimulcastConfig(kMinLayers, kMaxLayers, 480, 270,
+                                        kBitratePriority, kQpMax, !kScreenshare,
+                                        true, trials);
+  EXPECT_EQ(2u, streams.size());
+  // Lowest cropped height where max layers from higher resolution is used.
+  streams = cricket::GetSimulcastConfig(kMinLayers, kMaxLayers, 480, 252,
+                                        kBitratePriority, kQpMax, !kScreenshare,
+                                        true, trials);
+  EXPECT_EQ(2u, streams.size());
+  streams = cricket::GetSimulcastConfig(kMinLayers, kMaxLayers, 480, 250,
+                                        kBitratePriority, kQpMax, !kScreenshare,
+                                        true, trials);
+  EXPECT_EQ(1u, streams.size());
+}
+
 TEST(SimulcastTest, BitratesInterpolatedForResBelow180p) {
   // TODO(webrtc:12415): Remove when feature launches.
   test::ScopedFieldTrials field_trials(